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Evaluation of a Buried Vertical Well Leachate Recirculation System and Settlement Resulting from Moisture Addition using...

Permanent Link: http://ufdc.ufl.edu/UFE0024697/00001

Material Information

Title: Evaluation of a Buried Vertical Well Leachate Recirculation System and Settlement Resulting from Moisture Addition using Vertical Wells for Municipal Solid Waste Landfills
Physical Description: 1 online resource (194 p.)
Language: english
Creator: Kadambala, Ravi
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2009

Subjects

Subjects / Keywords: bioreactor, landfill, piezometers, pore, settlement, townsend, vertical
Environmental Engineering Sciences -- Dissertations, Academic -- UF
Genre: Environmental Engineering Sciences thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: An emerging waste management trend in the United States is to operate a landfill as a bioreactor. Effective moisture addition is the key to operating a bioreactor and this is most commonly accomplished using leachate recirculation. Vertical wells are relatively common in retrofit landfills. Vertical wells were installed to operate cell 1 and part of cell 2 as a bioreactor at the New River Regional Landfill (NRRL). Several lessons were learnt from the injection trials that prompted this research. This dissertation was organized into three main research objectives. The first objective was to evaluate the performance of a unique method for adding leachate in the landfill by burying the vertical wells. A cumulative volume of 8431 m3 (2.2 million gallons) of leachate was recirculated intermittently in the buried vertical well clusters over the period of 153 days. Leachate was injected under a pressure higher than the screen length of the vertical wells in the cluster without causing any surface seeps on the landfill. The average flow rate varied substantially from 9.3times10-4 to 14.2times10-4m3/sec (14.7 to 22.5 gpm) with increase in the well depth of the vertical well cluster from 6 to 9m. The entire screen length of the vertical wells in a cluster was not getting used during the initial period of leachate re-circulation due to a significant reduction in pressures between the first and the last vertical well in the cluster. Comparison of field test results indicated that the average leachate flow rate of the buried vertical well clusters was almost the same or higher compared to the conventional vertical wells. The second objective was to examine the temporal and spatial impact of leachate recirculation into buried vertical wells on the pore water pressure in the surrounding waste was investigated due to concerns with slope stability. The piezometers showed a steady increase in pore pressure in the surrounding waste over time and would continue to increase until the leachate addition in the well reached a steady state. Even though large pressures were present in the bottom of a buried vertical well during leachate injection it significantly reduced in the surrounding waste. Even though the hydrostatic head increased with the depth of the vertical well during leachate injection, the pore water pressure in the waste did not increase proportionally indicating that the permeability of waste was lower in the deeper sections of the landfill. Also there was a significant reduction in the pore water pressure in just few meters below the bottom of the buried vertical well which indicates the anisotropic nature of the waste. Thus, the stability of the landfill due to leachate addition in the buried vertical well may not be a concern if a suitable distance is maintained from the side slope of the landfill. The third objective was to evaluate the effect on landfill settlement resulting from moisture addition using vertical wells. The surface of the landfill settled an average of 2.48m (8.1ft) or 11.3% of the initial height in period of 5.3 years after bioreactor operations. The higher waste settlement was observed around the vertical wells with leachate addition compared to the vertical wells with no leachate addition. The average settlement percentage increased significantly between 0-800 m3 and 1600-2400 m3 of leachate addition. Settlement percentage was higher in the top and the bottom layers compared to the middle layers of the landfill due to leachate addition.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Ravi Kadambala.
Thesis: Thesis (Ph.D.)--University of Florida, 2009.
Local: Adviser: Townsend, Timothy G.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2011-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2009
System ID: UFE0024697:00001

Permanent Link: http://ufdc.ufl.edu/UFE0024697/00001

Material Information

Title: Evaluation of a Buried Vertical Well Leachate Recirculation System and Settlement Resulting from Moisture Addition using Vertical Wells for Municipal Solid Waste Landfills
Physical Description: 1 online resource (194 p.)
Language: english
Creator: Kadambala, Ravi
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2009

Subjects

Subjects / Keywords: bioreactor, landfill, piezometers, pore, settlement, townsend, vertical
Environmental Engineering Sciences -- Dissertations, Academic -- UF
Genre: Environmental Engineering Sciences thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: An emerging waste management trend in the United States is to operate a landfill as a bioreactor. Effective moisture addition is the key to operating a bioreactor and this is most commonly accomplished using leachate recirculation. Vertical wells are relatively common in retrofit landfills. Vertical wells were installed to operate cell 1 and part of cell 2 as a bioreactor at the New River Regional Landfill (NRRL). Several lessons were learnt from the injection trials that prompted this research. This dissertation was organized into three main research objectives. The first objective was to evaluate the performance of a unique method for adding leachate in the landfill by burying the vertical wells. A cumulative volume of 8431 m3 (2.2 million gallons) of leachate was recirculated intermittently in the buried vertical well clusters over the period of 153 days. Leachate was injected under a pressure higher than the screen length of the vertical wells in the cluster without causing any surface seeps on the landfill. The average flow rate varied substantially from 9.3times10-4 to 14.2times10-4m3/sec (14.7 to 22.5 gpm) with increase in the well depth of the vertical well cluster from 6 to 9m. The entire screen length of the vertical wells in a cluster was not getting used during the initial period of leachate re-circulation due to a significant reduction in pressures between the first and the last vertical well in the cluster. Comparison of field test results indicated that the average leachate flow rate of the buried vertical well clusters was almost the same or higher compared to the conventional vertical wells. The second objective was to examine the temporal and spatial impact of leachate recirculation into buried vertical wells on the pore water pressure in the surrounding waste was investigated due to concerns with slope stability. The piezometers showed a steady increase in pore pressure in the surrounding waste over time and would continue to increase until the leachate addition in the well reached a steady state. Even though large pressures were present in the bottom of a buried vertical well during leachate injection it significantly reduced in the surrounding waste. Even though the hydrostatic head increased with the depth of the vertical well during leachate injection, the pore water pressure in the waste did not increase proportionally indicating that the permeability of waste was lower in the deeper sections of the landfill. Also there was a significant reduction in the pore water pressure in just few meters below the bottom of the buried vertical well which indicates the anisotropic nature of the waste. Thus, the stability of the landfill due to leachate addition in the buried vertical well may not be a concern if a suitable distance is maintained from the side slope of the landfill. The third objective was to evaluate the effect on landfill settlement resulting from moisture addition using vertical wells. The surface of the landfill settled an average of 2.48m (8.1ft) or 11.3% of the initial height in period of 5.3 years after bioreactor operations. The higher waste settlement was observed around the vertical wells with leachate addition compared to the vertical wells with no leachate addition. The average settlement percentage increased significantly between 0-800 m3 and 1600-2400 m3 of leachate addition. Settlement percentage was higher in the top and the bottom layers compared to the middle layers of the landfill due to leachate addition.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Ravi Kadambala.
Thesis: Thesis (Ph.D.)--University of Florida, 2009.
Local: Adviser: Townsend, Timothy G.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2011-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2009
System ID: UFE0024697:00001


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1 EVALUATION OF A BURIED VERTICAL WELL LEACHATE RECIRCULATION SYSTEM AND SETTLEMENT RESULTING FROM MOISTURE ADDITION USING VERTICAL WELLS FOR MUNICIPAL SOLID WASTE LANDFILLS By RAVI SHANKAR KADAMBALA A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2009

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2 2009 Ravi Shankar Kadambala

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3 To my advisor, parents and loving wife

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4 ACKNOWLEDGMENTS I would like to express my sincerest gratitude and appreciation to the chairman of my committee, Dr. Timothy G. Townsend, for his guidance, patience and support though out my graduate study at University of Flor ida. It was indeed a great privilege and an honor to work with him I will always be indebted to him for mentoring me as a researcher and training me for the professional world. I would also like to thank the other members of my committee, Dr. Michael D. A nnable, Dr. David Bloomquist, and Dr. Louis H. Motz for their participation and guidance. This work was funded by the Hinkley Center for Solid and Hazardous Waste Management (HCSHWM) and the New River Solid Waste Authority (NRSWA) I am thankful to Darrel l ONeal, Executive Director, Perry Kent and Lydia Greene of NRSWA for their guidance, support and believing in me to conduct research in the landfill Special thanks go to Richard Crews and David Mckinney for their relentless help throughout the construct ion of my project. I am thankful to John Schert of FCSHWM for his active support and encouragement in spite of accidently crashing one of the state vehicles. I would like to thank Dr. Pradeep Jain, Dr. Jae Hac Ko, Youngmin Cho and Karamjit Singh for providing me with excellent support in planning research and valuable inputs on data analysis. I also acknowledge the support of my friends and fellow graduate students especially Shrawan Singh, Dr. Hwidong Kim, Dr. Dinesh Kumar, Aaron Jordan and Dr. Qiyong Xu for their assistance and cooperation in this work. Last, but not least, I would like to thank my wife Anupama Sahu for her understanding and love during the past few years. Her support and encouragement was in the end what made this dissertation possible. My family, Adinarayana and Indira receive my deepest gratitude and love for their dedication and the many years of support during my undergraduate studies that provided the foundation for this work.

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5 TABLE OF CONTENTS ACKNOWLEDGMENTS ...............................................................................................................4 page LIST OF TABLES ...........................................................................................................................8 LIST OF FIGURES .........................................................................................................................9 ABSTRACT ...................................................................................................................................18 CHAPTER 1 INTRODUCTION ..................................................................................................................20 1.1 Background .......................................................................................................................20 1.2 Problem Stat ement ............................................................................................................22 1.3 Research Objectives ..........................................................................................................24 1.4 Research Approach ...........................................................................................................26 1.5 Outline of Proposal ...........................................................................................................27 2 EVALUATION OF A BURIED VERTICAL WELL LEACHATE RECIRCULATION SYSTEM FOR MUNICIPAL SOLID WASTE LANDFILLS ..............................................28 2.1 Introduction .......................................................................................................................28 2.2 Materials and Methods .....................................................................................................30 2.2.1 Site Description ......................................................................................................30 2.2.2 Concept of Buried Vertical Well Clusters ..............................................................31 2.2.3 Experimental Set up and Construction of the Buried Vertical Well Clusters ........32 2.2.4 System Operation and Monitoring .........................................................................34 2.3 Results and Discussion .....................................................................................................35 2.3.1 Overall Performance ...............................................................................................35 2.3.2 Performance of a Vertical Well Cluster .................................................................37 2.3.3 Comparison of two Buried Vertical Well Clusters With the Same Depth .............38 2.3.4 Impact of Well Depth on the Performance of the Vertical Well Clusters ..............39 2.3.5 Comparison of Field Test Results of Buried Vertical We lls with Conventional Vertical Wells ..............................................................................................................41 2.3.6 Assessment of Technology .....................................................................................41 3 TEMPORAL AND SPATIAL PORE WATER PRESSURE DISTRIBUTION SURROUNDING VERTICAL LANDFILL LEACHATE RECIRCULATION WELL ......53 3.1 Introduction .......................................................................................................................53 3.2 Materials and Methods .....................................................................................................55 3.2.1 Site Description ......................................................................................................55 3.2.2 Experiment Set up and Construction ......................................................................56

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6 3.2.3 Sys tem Operation and Monitoring .........................................................................57 3.2.4 Data Management ...................................................................................................58 3.3 Results and Discussion .....................................................................................................59 3.3.1 Overall Sensor Performance ...................................................................................59 3.3.2 Pore Pressures in the Waste before Leachate Recirculation ..................................59 3.3.3 Hydrodynamic Lag Time in Reading the Pore Water Pressure by the Piezometer Encased in Grout .......................................................................................60 3.3.4 Piezometer Responses in the Initial Period of Leachate Re circulation .................61 3.3.5 Temporal Impact of Leachate Recirculation on the Pore Pressure in the Surrounding Waste .......................................................................................................63 3.3.6 Spatial impact of leachate recirculatio n on the pore pressure in the S urrounding waste .......................................................................................................64 3.3.7 Implications of t his Research with Side Slope Stability ........................................66 3.4 Conclusi on ........................................................................................................................67 4 LANDFILL SETTLEMENT RESULTING FROM MOISTURE ADDITION USING VERTICAL WELLS ..............................................................................................................79 4.1 Introduction .......................................................................................................................79 4.2 Materials and Methods .....................................................................................................81 4.2.1 Site Configuration ..................................................................................................81 4.2.2 Operation of the Bioreac tor ....................................................................................82 4.2.3 Settlement and Moisture Content Measurements ...................................................83 4.2.4 Data Management ...................................................................................................84 4.3 Results and Discussion .....................................................................................................85 4.3.1Settlement and the Average Space Gained Over the Bioreactor Operation Period ...........................................................................................................................85 4.3.2 Total Settlement at Various Cross Sections of the Bioreactor ...............................87 4.3.3 Settlement in Various Layers of the Landfill .........................................................88 4.3.4 Lateral Settlement around the Vertical Well Clusters ............................................89 4.3.5 Impact of Leachate Addition on Settlement in Various Sections of the Landfill .........................................................................................................................90 4.3.6 Impact of Leachate Addition on the Settlement in Various Layers of the Landfill .........................................................................................................................91 4.4 Conclusion ........................................................................................................................92 5 SUMMARY AND CONCLUSIONS .....................................................................................99 5.1 Summary ...........................................................................................................................99 5.2 Conclusion ......................................................................................................................103 5.3 Future work .....................................................................................................................104 APPENDIX A CONSTRUCTION PHOTOS OF THE BURIED VERTICAL WELL CLUSTERS ..........106 B HEAD LOSS DUE TO FRICTION .....................................................................................109

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7 C PRESSURE AND TEMPERATURE DATA OF THE BURIED VERTICAL WELL CLUSTERS ..........................................................................................................................113 D CONSTRUCTION PHOTOS OF THE EXPERIMENTAL SETUP TO MEASURE PORE PRESSURE DISTRIBUTION IN A LANDFILL .....................................................118 E EXPERIMENTAL SETUP AND RESULTS TO DETERMINE THE HYDRODYNAMIC LAG TIME OF PIEZOMETERS ENCASED IN GROUT ...............120 F UNIT CONVERSION AND NORMAILIZATION OF VW PIEZOMETERS ...................124 F.1 Calculation to Convert Pore Pressure Measured in Frequency to Units of Pressure .....124 F.2 Normalization of Pore Pressure Data of a Piezometer ...................................................124 F.3 Example of Piezometers not Considered for Analysis ...................................................126 G PORE PRESSURE AND TEMPERATURE OF INDIVIDUAL PIEZOMETERS .............128 H ESTIMATION OF POTENTIAL PORE PRESSURE DISTRIBUTION IN A LANDFILL ...........................................................................................................................180 I SUPPLEMENTAL FIGURES AND GRAPHS TO DETERMINE SETTLEMENT IN A BIOREACTOR LANDFILL DUE TO MOISTURE ADDITION .......................................182 J ESTIMATION OF PREDICTED SETTLEMEN T ..............................................................187 LIST OF REFERENCES .............................................................................................................191 BIOGRAPHICAL SKETCH .......................................................................................................195

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8 LIST OF TABLE S Table page 21 Field injection test result of buried vertical wells clusters .................................................51 22 Comparison of field test results of buried vertical well clu sters with different depths .....51 23 Comparison of field test results of buried vertical well clusters with vertical wells .........52 B 1 Total head loss of the leachate in a pipe due to friction...................................................112 E 1 Hydrodynamic lag time in reading the pore water pressure by the VW piezometer encased in grout due to transition from unsatura ted to saturated media as a result of leachate addition ..............................................................................................................123 J 1 Mechanical settlement occurring in the various layers of the landfill due to the overburden pressure of the leachate addition ...................................................................188

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9 LIST OF FIGURE S Figure page 31 Plan view of NRRL indicating the buried vertical well clusters .......................................69 32 Plan view of the buried vertical wells and the multi level piezometer wells .....................70 33 Cross section view of the buried vertical wells and the multi level piezometer wells ......70 34 Pore pressures measured by the VW Piezometers at various depths inside the landfill prior to leachate recirculation ............................................................................................71 35 P iezometer responses to leachate recirculation at various depths and at a fixed radial distance of 1.5m from the well during the first few days of operation at an average flow rate of 13.67104 m3/sec ...........................................................................................72 36 Piezometer responses to leachate recirculation in radial direction from the vertical well during the first few days of operation at an average flow rate of 13.67104 m3/sec .................................................................................................................................73 37 Temporal impact of leachate injection on the pore pressures of surrounding waste in radial direction and at a depth of (a) 5.8 m, (b) 8.8 m, (c) 11.9 m, (d) 14.9 m and (e) 18 m from the surface of the landfill .................................................................................75 38 Spatial impact on the pore pressures of surrounding waste in radial direction and at a depth of (a) 5.8 m, (b) 8.8 m, (c) 14.9 m and (d) 18 m from the surface of the landfill during leachate recirculation at a pressure of 20 m of w.c.at the bottom of the buried vertical well and a flow rate was 6 x 104 m3/s ..................................................................76 39 Spatial impact on the pore pressures of surrounding waste in vertical direction and at a radial dista nce of (a) 2.15 m, (b) 3 m, (c) 6.3 m and (d) 7.8 m from the buried vertical well during leachate recirculation at a pressure of 20 m of w.c.at the bottom of the buried vertical well and a flow rate was 6 x 104 m3/s .............................................78 41 Plan view of new river regional landfill indicating the bioreactor area (Adapted from as built drawings provided by Jones Edmunds and Associates) .......................................93 42 Schemat ic view of a vertical well cluster and monitoring wells .......................................94 43 Settlement at the surface and at various depths in the landfill over time with leachate recirculation .......................................................................................................................94 44 Air space gained from the surface of the landfill and at various depths along with the cumulative volume of leachate recirculated over time ......................................................95 45 C ross section of the landfill indicating the change in landfill surface due to settlement over period of 5.35 years ..................................................................................96

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10 46 Settlement percentage in various layers of the landfill ......................................................96 47 Average lateral settlement from the vertical wells with and without leachate addition ....97 48 Average settlement due to leachate additio n in various sections of the landfill ................97 49 Settlement due to leachate addition in the inner sections of the landfill ...........................98 A 1 Dr illing a vertical well in a trench using the solid stem open flight auger drilling rig on the surface of the landfill. ...........................................................................................106 A 2 Pointed tail bit attached to the tip of the solid stem open fligh t auger .............................106 A 3 Insertion of slotted pipe through the temporary HDPE pipe ...........................................107 A 4 Customized pipe assembly being placed inside t he drilled vertical well .........................107 A 5 Datalogger to measure and record pressure and temperature data from the piezometers and thermocouple wires ...............................................................................108 C 1 Change in pressure and temperature at the bottom of the first vertical well in the 6m well depth cluster of section I due to leachate recirculation ............................................113 C 2 Change in pressu re and temperature at the bottom of the last vertical well in the 6m well depth cluster of section I due to leachate recirculation ............................................114 C 3 Change in pressure and temperature at the bottom of t he first vertical well in the 9m well depth cluster of section I due to leachate recirculation ............................................114 C 4 Change in pressure and temperature at the bottom of the first vertical well in the 12m we ll depth cluster of section I due to leachate recirculation ............................................115 C 5 Change in pressure and temperature at the bottom of the first vertical well in the 6m well depth cluster of section II due t o leachate recirculation ...........................................115 C 6 Change in pressure and temperature at the bottom of the last vertical well in the 9m well depth cluster of section II due to leachate recirculation ...........................................116 C 7 Change in pressure and temperature at the bottom of the first vertical well in the 12m well depth cluster of section II due to leachate recirculation ...........................................116 C 8 Change in pressure and temperature at the bottom of the last vertical well in the 12m well depth cluster of section II due to leachate recirculation ...........................................117 D 1 Hollow s tem open flight auger being used for drilling ....................................................118 D 2 Assembling part of multilevel piezometer assembly ......................................................118 D 3 Installation of the multilevel piezometer in the borehole with a crane ..........................119

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11 D 4 Grouting of Multi level VW piezometer assembly .........................................................119 E 1 Experime ntal set up to determine the hydrodynamic lag time in reading the pore water pressure by a VW piezometer encased in grout .....................................................121 E 2 Time taken by the piezometer to fully dissipate the water that was used to make the grout mixture to the surrounding sand media ..................................................................122 F 1 Pore pressure data measured the piezometer since calibration by the manufacturer .......125 F 2 Actual pore pressure measured a VW piezometer since starting leachate addition on day 1313 ...........................................................................................................................125 F 3 Normalized pore pressure measured a VW piezometer since st arting leachate addition on day 1313 ........................................................................................................126 F 4 An example of a VW piezometer that was not considered for interpretation of results due to highly erratic and fluctuating pore water pressure data ........................................127 G 1 Pore pressure and temperature data of piezometer A1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recircu lation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................129 G 2 Pore pressure and temperature data of piezometer A2: (a) Pore pressure over time from the calibratio n day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................130 G 3 Pore pressure an d temperature data of piezometer A4: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................131 G 4 Pore pressure and temperature data of piezometer B1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculati on, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................132 G 5 Pore pressure and temperature data of piezometer B2: (a) Pore pressure over time from the calibration da y, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................133 G 6 Pore pressure and te mperature data of piezometer B3: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................134

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12 G 7 Pore pressure and temperature data of piezometer B4: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................135 G 8 Pore pressure and temperature data of piezometer B5: (a) Pore pressure over time from the calibration day, ( b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................136 G 9 Pore pressure and temper ature data of piezometer C1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................137 G 10 Pore pressure and temperature data of piezometer C2: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................138 G 11 Pore pressure and temperature data of piezometer C3: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................139 G 12 Pore pressure and tempera ture data of piezometer C5: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................140 G 13 Pore pressure and temperature data of piezometer D1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................141 G 14 Pore pressure and temperature data of piezometer D3: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................142 G 15 Pore pressure and temperat ure data of piezometer D5: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................143 G 16 Pore pressure and temperature data of piezometer G1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning

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13 of leachate recirculation, (c) N ormalized pore pressure during the initial days of leachate injection. ............................................................................................................144 G 17 Pore pressure and temperature data of piezometer G2: (a) Pore pressure over time from the calibration day, (b) N ormalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................145 G 18 Pore pressure and temperatu re data of piezometer G5: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................146 G 19 Pore pressure and temperature data of piezometer H3: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) No rmalized pore pressure during the initial days of leachate injection. ............................................................................................................147 G 20 Pore pressure and temperature data of piezometer E1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................148 G 21 Pore pressure and temperatur e data of piezometer E2: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................149 G 22 Pore pressure and temperature data of piezometer F1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Nor malized pore pressure during the initial days of leachate injection. ............................................................................................................150 G 23 Pore pressure and temperature data of piezometer F3: (a) Pore pressure over time from the calibration day, (b) Nor malized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................151 G 24 Pore pressure and temperature data of piezometer F5: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................152 G 25 Pore pressure and temperature data of piezometer I1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Norm alized pore pressure during the initial days of leachate injection. ............................................................................................................153

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14 G 26 Pore pressure and temperature data of piezometer I2: (a) Pore pressure over time from the calibration day, (b) Norm alized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................154 G 27 Pore pressure and temperature data of piezometer I3: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................155 G 28 Pore pressure and temperature data of piezometer I4: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................156 G 29 Pore pressure and temperature data of piezometer J2: (a) Pore pressure over time from the calibration day, (b) Norma lized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................157 G 30 Pore pressure and temperature d ata of piezometer K1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................158 G 31 Pore pressure and temperature data of piezometer K2: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normal ized pore pressure during the initial days of leachate injection. ............................................................................................................159 G 32 Pore pressure and temperature data of piezometer L1: (a) Pore pressure over time from the calibration day, (b) Normal ized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................160 G 33 Pore pressure and temperature da ta of piezometer L2: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................161 G 34 Pore pressure and temperature data of piezometer L3: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normali zed pore pressure during the initial days of leachate injection. ............................................................................................................162 G 35 Pore pressure and temperature data of piezometer L4: (a) Pore pressure over time from the calibration day, (b) Normali zed pore pressure over time from the beginning

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15 of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................163 G 36 Pore pressure and temperature dat a of piezometer L5: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................164 G 37 Pore pressure and temperature data of piezometer M2: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normaliz ed pore pressure during the initial days of leachate injection. ............................................................................................................165 G 38 Pore pressure and temperature data of piezometer M3: (a) Pore pressure over time from the calibration day, (b) Normaliz ed pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................166 G 39 Pore pressure and temperature data of piezometer O1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................167 G 40 Pore pressure and temperature data of piezometer O2: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................168 G 41 Pore pressure and temperature data of piezometer O3: (a) Pore pressure over time from the calibration day, (b) Normalize d pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................169 G 42 Pore pressure and temperature data of piezometer Q4: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................170 G 43 Pore pressure and temperature data of piezometer Q5: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................171 G 44 Pore pressure and temperature data of piezometer P1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................172

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16 G 45 Pore pressure and temperature data o f piezometer P2: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................173 G 46 Pore pressure and temperature data of piezometer P3: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................174 G 47 Pore pressure and temperature data of piezometer P4: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................175 G 48 Pore pressure and temperature data of piezometer P5: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................176 G 49 Pore pressure and temperature data of piezometer R1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized p ore pressure during the initial days of leachate injection. ............................................................................................................177 G 50 Pore pressure and temperature data of piezometer R2: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................178 G 51 Pore pressure and temperature data of piezometer R3: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. ............................................................................................................179 H 1 Gas pressure distribution within in the landfill for different permeability of waste ........181 H 2 Gas pressure distribution within in the landfill for different gas collection rates for the leachate collection system ..........................................................................................181 I 1 Plan view showing the location of injection clusters (Adapted from as built drawings provided by Jones Edmunds and Ass ociates) ..................................................................182 I 2 Elevation contours of the bioreactor landfill in 2002 and 2007 .......................................183 I 3 Schematic diagram of various sections of the bioreactor area along the corresponding settlement % and the amount of liquids injected .............................................................184

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17 I 4 Percentage Settlement vs. moisture content in various layers of a landfill .....................185 I 5 Moisture content at different depths in the bioreactor area of the landfill in 2007 .........186 J 1 Leachate added in the various layers of the landfill ........................................................190

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18 Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy EVALUATION OF A BURI ED VERTICAL WELL LEACHATE RECIRCULATION SYSTEM AND SETTLEMENT RESULTING FROM MOISTURE ADDITION USING VERTICAL WELLS FOR MUNICIPAL SOLID WASTE LANDFILLS By Ravi Shankar Kadambala December 2009 Chair: Timothy G. Townsend Major: Environmental Engineering S ciences An emerging waste management trend in the United States is to operate a landfill as a bioreactor. E ffective moisture addition is the key to operating a bioreactor and this is most commonly accomplished using l eachate recirculation Vertical wells are relatively common in retrofit landfills Vertical wells were installed to operate cell 1 and part of cell 2 as a bioreactor at the New River Regional Landfill (NRRL). S everal lessons were learnt from the injection trials that prompted this research. T his dissertation was organized into three main research objectives. The first objective was to evaluate the performance of a unique method for adding leachate in the landfill by burying the vertical wells. A cumulative volume of 8431 m3 (2.2 million gallon s) of leachate was recirculated intermittently in the buried vertical well clusters over the period of 153 days Leachate was injected under a pressure higher than the screen length of the vertical wells in the cluster without causing any surface seeps on the landfill. The average flow rate varied substantially from 9.3104 to 14.2104m3/sec (14.7 to 22.5 gpm) with increase in the well depth of the vertical well cluster from 6 to 9m. The entire screen length of the vertical wells in a cluster was not gett ing used during the initial period of leachate re circulation due to a significant reduction in pressures between the first and the l ast vertical well in the cluster.

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19 Comparison of field test results indicated that the average leachate flow rate of the bur ied vertical well clusters was almost the same or higher compared to the conventional vertical wells. The second objective was to examine the temporal and spatial impact of leachate recirculation into buried vertical wells on the pore water pressure in the surrounding waste was investigated due to concerns with slope stability. The piezometers showed a steady increase in pore pressure in the surrounding waste over time and would continue to increase until the leachate addition in the well reached a steady s tate. Even though large pressures were present in the bottom of a buried vertical well during leachate injection it significantly reduced in the surrounding waste. Even though the hydrostatic head increased with the depth of the vertical well during leacha te injection, the pore water pressure in the waste did not increase proportionally indicating that the permeability of waste was lower in the deeper sections of the landfill. Also there was a significant reduction in the pore water pressure in just few met ers below the bottom of the buried vertical well which indicates the anisotropic nature of the waste. Thus, the stability of the landfill due to leachate addition in the buried vertical well may not be a concern if a sui t able distance is maintained from th e side slope of the landfill. The third objective was to evaluate the effect on landfill settlement resulting from moisture addition using vertical wells The surface of the landfill settled an average of 2.48m (8.1ft) or 11.3% of the initial height in per iod of 5.3 years after bioreactor operations The higher waste settlement was observed around the vertical wells with leachate addition compared to the vertical wells with no leachate addition. The average settlement percentage inc reased significantly betw een 0 800 m3 and 16002400 m3 of leachate addition. Settlement percentage was higher in the top and the bottom layers compared to the middle layers of the landfill due to leachate addition.

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20 CHAPTER 1 INTRODUCTION 1.1 Background In 2005, U.S. residents, businesses, and institutions produced more than 245 million tons of municipal solid waste (MSW), which is approximately 4.5 pounds of waste per person per day (US EPA 2007). M SW, more commonly known as trash or garbage, is managed in several ways including source reduction, recycling, composting, disposal in landfills, or incineration. According to the Environmental Protection Agency (EPA), currently 32 percent of MSW is recove red and recycled or composted, 14 percent is burned at combustion facilities, and the remaining 54 percent is disposed of in landfills in the United States. Landfills have evolved in the last two decades, moving from open dumps with little or no control into a controlled and sophisticated containment systems. Within a MSW landfill, biological, chemical, and physical processes occur that result in the degradation of wastes and the production of leachate and gas (Pohland 1975, Reinhart and Townsend 1998). Conventional landfills in the United State are designed and operated in accordance with the principles described in Subtitle D of the Resource Conservation and Recovery Act (RCRA) and are equipped with liners, caps, and a leachate collection system. The waste in these landfills may take a long time to degrade or decompose, resulting in the need to care for these facilities indefinitely into the future. Alternatively, a landfill operated as a bioreactor rapidly transforms and degrades organic waste (US EPA 200 7, Pohland 1999), thus reducing the long term impacts and needed care of the facility. A bioreactors increase in waste degradation and stabilization is accomplished through the addition of moisture and possibly air to enhance microbial processes (Reinhart and Townsend 1998). The Solid Waste Association of North America (SWANA) has defined a bioreactor landfill as "any permitted Subtitle D landfill or landfill cell where leachate or air is

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21 injected in a controlled fashion into the waste mass in order to acc elerate or enhance biostabilization of the waste (US EPA 2009). Three types of bioreactor landfill configurations are commonly referred to. The anaerobic bioreactor utilizes moisture addition to the waste mass (in the form of re circulated leachate and ot her sources) to promote biodegradation in the absence of oxygen (anaerobically). With an aerobic bioreactor landfill, air is injected into the waste mass in addition to adding moisture to promote and accelerate aerobic waste stabilization. In some bioreact or landfill operations, waste degradation is enhanced by employing a sequential aerobic anaerobic treatment to rapidly degrade organics in the upper sections of the landfill and collect gas from the lower sections. The objective of the sequential aerobic a naerobic treatment is to cause the rapid biodegradation of food and other easily degradable waste in the aerobic stage in order to reduce the production of organic acids in the anaerobic stage resulting in the earlier onset of methanogenesis (Waste Managem ent 2004, John Pichtel 2005). The potential advantages of bioreactor landfills include: Decomposition and biological stabilization in years vs. decades in dry tombs (Pohland et al 1999) Reduced leachate treatment and disposal costs (Pohland et al 1999) Greater flexibility in leachate management and treatment (Khire et al. 2006) Reduced risk associated with contamination from spills during off site transportation, treatment, and disposal of leachate (Khire et al 2006) 15 to 30 percent gain in landfill space due to an increase in the density of waste mass (El Fadel et al 1999) Significantly increased LFG generation that when captured can be used for energy use onsite or sold (Barlaz et al 1990) Reduced post closure care (Pohland et al 1975, 1980) Bior eactor landfills also have a few disadvantages. These disadvantages include reduction in the shear strength of MSW potentially reducing the factor of safety against slope stability of the landfill, potential leachate breakouts from the sides of the landfil l, increase in the leachate head build up on the liner potentially increasing the risk for ground water contamination,

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22 increase in the landfill gas production increasing the risk of harmful green house gases entering the atmosphere (Khire et al 2006; Ha yd ar et al 2005). Over the past couple of decades several investigations have been done on various aspects of the bioreactor processes to make bioreactor a viable option for solid waste management (Pohland et al 1975, 1980; Pohland et al 1999; Townsend et al 1996; Reinhart et al 1997, 2002; Mehta et al 2002). 1.2 Problem Statement An effective moisture addition system is a key element in operating a bioreactor (Townsend et al. 1996). Vertical injection wells and horizontal trenches are the two most c ommon methods of subsurface leachate recirculation. Both these types of leachate injection methods can inject relatively large quantities of leachate in the subsurface landfill, offer minimum exposure pathways, and provide good all weather performance. Ho rizontal trenches are more commonly used in modern lined landfills. Vertical wells are relatively common in retrofit landfills where it is not cost effective or not possible to install horizontal trenches. Several full scale bioreactor landfills have been implemented in US to evaluate the operation and performance of bioreactor landfills (Jain et al 2005; Pacey et al. 1999; Zhao et al 2008; Benson et al. 2006). One such full scale bioreactor is at the New River Regional Landfill (NRRL) located in Union C ounty, Florida. The NRRL receives approximately 1000 metric tons per day of waste consisting of mixed residential and commercial waste. The landfill currently consists of five contiguous lined landfill cells totaling approximately 30 hectares Approximat ely 4 hectares (Cell 1 and part of Cell 2) were retrofitted to operate as a bioreactor landfill. A detailed description of the site and the bioreactor can be found e lsewhere ( Jain et al. 2005). Jain et al. (2005) evaluated the performance of vertical well s for landfill leachate recirculation and several lessons were learnt that prompted this research.

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23 I njection trials conducted found surface seeps to occur around the injection wells if liquids were added at a hydrostatic head above the surface of the land fill. A large number of vertical wells penetrating the surface geomembrane contributed to air intrusion into the gas collection system which reduced the efficiency of the gas collection system. Differential settlement was observed around the vertical clust ers due to leachate addition resulting in an uneven surface of the landfill at the end of the bioreactor operation. Also, recirculating leachate at a constant pressure below the surface of the landfill required constant monitoring of the system a nd check f or seeps. T he se vertical wells had to be dismantled to add more waste on surface of landfill. I n an attempt to solve some of the limitations associated with vertical wells t his research evaluated the performance of a unique method for adding leachate in the landfill by burying the vertical wells in a layer of waste During the period of operation of the landfill as a bioreactor at NRRL, over 6 million gallons of liquid was added. The addition of leachate accelerates decomposition of the refuse in bioreact ors considerably changing the geotechnical characteristics of the waste in the landfill, and thereby increases the concern for waste stability (Hossain et al. 2009). The Dona Juana Landfill was the central solid waste disposal facility for Bogata, Columbi a and treated leachate by recirculating it back into the landfill. The catastrophic slope failure of the Dona Juana Landfill (Hendron et al. 1999; Gonzalez Garcia and Espinosa Silva 2003) showed that the design and analysis methods established for dry landfills where pore pressures within the waste are not considered may not be appropriate for wet or bioreactor landfills. Jain et al. (2005) have mathematically modeled the impact of leachate recirculation into vertical wells on the pore water pressure of the surrounding waste in the landfill, but very little is known about the pressures that actually develop within landfills as a result of added liquids. So, one of the objectives of this research

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24 was to examine the temporal and spatial impact of leachate reci rculation into buried vertical wells on the pore water pressure in the surrounding waste. Since operating the NRRL landfill as a bioreactor, the landfill has settled an average of 8.124 ft. The settlement mechanisms in MSW landfills are complex as compared with typical soil consolidation. Settlement in a landfill is due to primary and secondary settlement that occurs simultaneously (Park et al. 1997, 2002; Ling et al. 1998; Durmusoglu et al. 2005; Kim 2007). Primary settlement takes place within the first f ew months after the placement of waste due to overburden pressure. The determination of secondary settlement in a landfill is a major concern as this account for majority of the settlement. This settlement is mainly due to the decomposition of organic was te. The increase in waste degradation and stabilization is accomplished through the addition of moisture to enhance microbial processes in an anaerobic bioreactor landfill. In addition to this in a bioreactor landfill, moisture addition increases the speci fic weight of the waste in a bioreactor landfill. Increased specific weight results in greater mechanical settlement of the landfill. The compacted nature of the waste in a landfill exhibits heterogeneous and anisotropic material property that makes prediction of settlement over time very challenging. While the literature has reported some field settlement observations ( Ramin Yazdani et al. 1999; El Fadel et al. 1999; Benson et al. 2007) no attempt has been made to relate the amount of leachate recirculated or the moisture content of the waste to the settlement in a bioreactor landfill. 1.3 Research Objectives The purpose of this doctoral research was to explore some of the specific aspects of bioreactor design and operation. Some of the experiments conducted at the site and in the lab are described in this dissertation.

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25 The first objective was to inject leachate in the buried vertical wells at a pressure higher than the screen length of the vertical well without causing surface seeps on the landfill. Six buried vertical well clusters were installed in cell 4 of NRRL. The clusters had a depth of 6, 9, and 12 m respectively wit h replicates. Each cluster had nine vertical wells connected to a single lateral leachate recirculation line via manifold system. T wo piezometers and two thermocouples were placed at the bottom of the vertical wells to measure pressure and temperature respectively in each cluster Also, each of the lateral leachate recirculation lines had a flow meter and pressure gauge to measure flo wrate, cumulative volume and pressure for every buried vertical well cluster A lift of waste was placed on top to bury the vertical well clusters. The second objective was to examine the temporal and spatial impact of leachate recirculation into buried vertical wells on the pore water pressure in the surrounding waste in a full scale MSW landfill. Two 12.2 m deep buried vertical wells were drilled at a distance of 7.6 m from each other in cell 4 of NRRL. Surrounding these vertical wells were 18 multi leve l VW piezometer wells at a distance of 1.5 m from each other. Each multi level VW piezometer wells had five VW piezometers at a distance of three meters from each other. All the piezometers were connected to a datalogger to measure, and recorded pore press ure and temperature spatially from the buried vertical wells in the surrounding waste. A lift of waste was placed on top to the experimental set up to bury the vertical wells and the piezometers. Both the lateral leachate recirculation lines had a flow me ter and pressure gauge to measure flowrate, cumulative volume and injection pressure of leachate in the buried vertical wells. The third objective was to evaluate the effect on landfill settlement resulting from moisture addition using vertical wells based on the settlement investigation conducted in the bioreactor area of the landfill at NRRL Because of the way waste in a landfill is deposited and compacted

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26 in thin layers; it is commonly regarded as anisotropic (Townsend et al. 1995; McCreanor et al. 1998; Landva et al. 1998). So, one of the objectives of this research was to characterize the settlement in various layers of the landfill, and the impact of moisture content on the settlement in various layers of the landfill. 1.4 Research Approach Objective 1. To inject leachate in buried vertical wells at a pressure higher than the screen length of the vertical well without causing surface seeps on the landfill Approach. L eachate re circulation was carried out i n the buried vertical well clusters at differen t depths for a period of 153 days The flowrate and leachate injection pressure and pressure at the bottom of the vertical wells during leachate re circulation were monitored to assess the hydraulic performance of the buried vertical well clusters A relat ionship between flowrate and pressure for the well clusters a t various depths were developed. The average flow rate, and flowrate per unit screen length of the buried vertical well clusters were compared with conventional vertical wells. Objective 2. To e valuate the temporal and spatial impact of leachate recirculation into buried vertical wells on the pore water pressure in the surrounding waste in a full scale MSW landfill Approach. Leachate recirculation was carried out intermittently in the main buried vertical well for a period of 122 days The flowrate, leachate injection pressure cumulative volume of leachate injected, and t he change in pore water pressure and temperature in all the piezometer s was closely monitored during and after leachate re circulation over time. Surfer software and sigma plot 10.0 were used to determine and evaluate the change in pore water pressure surrounding the waste spatially and temporally from the buried vertical well

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27 Objective 3 To evaluate the effect on landfill settlement resulting from moisture addition using vertical wells. Approach. Leachate re circulation was carried out intermittently in the bioreactor area from 2003 until 2007. The cumulative volume of leachate added was recorded for each vertical well cluster. The settlement of the waste at the surface and at different depths was monitored though out the period of bioreactor operation. Several waste samples were augured before and after the bioreactor operation to measure the moisture content at different loca tions and depths within the bioreactor area. The overall air space gained by the bioreactor and the rate of settlement in various layers for the landfill was calculated. The bioreactor area was divided into 16 equal sections of area 2525m2. For each of these sections, the cumulative volume of leachate added and the overall settlement was calculated. T he rate of settlement was characterized based on the amount of leachate added in the various sections of the landfill Each of these sections was further divi ded into various layers to characterize the impact of leachate addition on the settlement in various layers of the landfill. 1.5 Outline of Proposal The dissertation is presented in six chapters. Chapter 1 presents introduction, problem statement, objectiv es and research approach. Chapters 2 to 4 are classified into three stand alone manuscripts. Chapter 2 evaluates the buried vertical well leachate recirculation system for municipal solid waste landfills Chapter 3 evaluates the temporal and spatial impac t of leachate recirculation into vertical wells on the pore water pressure in the surrounding waste. Chapter 4 characterizes the landfill settlement resulting from moisture addition using vertical wells f rom the available data of the full scale bioreactor at the New River Regional Landfill, Raiford. C hapter 5 presents a summary, conclusions and recommendations for future work.

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28 CHAPTER 2 EVALUATION OF A BURI ED VERTICAL WELL LEA CHATE RECIRCULATION SYSTEM FOR MUNICIPAL SOLID WASTE LANDFILL S 2.1 Introduction An emerging waste management trend in the United States is to operate a landfill as a bioreactor. The waste in bioreactor landfills undergo faster stabilization compared to conventional landfills by creating an in situ environment conducive to microbial degradation of waste, such as through the addition of moisture and possibly air to enhance microbial processes (Reinhart and Townsend 1998). Effective moisture addition is the key to operating a bioreactor (Townsend et al. 1996) and this is most commonly a ccomplished using leachate recirculation. Multiple pilot studies and full scale landfills have demonstrated the benefits of leachate recirculation (Pohland et al. 1975, 1980; Leckie et al. 1979; Buivid et al. 1981; Barber and Maris 1984, Na tale and Anders on 1985; Watson et al. 1987). Leachate recirculation can be accomplished in several ways including prewetting, spraying, surface ponds, horizontal infiltration systems and vertical injection wells. The hydraulic properties of the municipal solid waste gre atly impact the effectiveness of the chosen recirculation method (McCreanor and Reinhart 1999; Rosqvist and Destouni 2000; Rosqvist et al. 2005). Vertical injection wells and horizontal trenches are the two most common methods of leachate recirculation as they can inject relatively large quantities of leachate, offer minimum exposure pathways and provide good all weather performance (Townsend et al. 1995; Reinhart and Al Yousfi 1996; Miller and Emge 1997; Warith et al. 2001; Mehta et al. 2002; Jain et al. 2005; Haydar and Khire 2005; Benson et al. 2007; Khire and Mukherjee 2007). Horizontal trenches are more commonly used in modern lined landfills. Vertical wells are relatively common in retrofit landfills where it is not cost effective or not possible to in stall horizontal trenches.

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29 Several full scale bioreactor landfills have been implemented in the US to evaluate the performance of vertical wells for recirculating leachate in bioreactor landfills (Reinhart et al. 1995; Jain et al. 2005; Benson et al. 2007). One such full scale bioreactor is at the New River Regional Landfill (NRRL) located in Union County, Florida. NRRL landfill was not initially designed for bioreactor operation and it was retrofitted with vertical wells after the final waste elevation i n the test area was reached. Vertical wells were preferred over surface trenches or an infiltration pond because thick layers of the low permeability cover material (clayey sand) would hamper the downward movement of moisture from the surface type moistur e addition system. While designing the vertical well system, it was hypothesized that most of the liquid would flow through the bottom portion of a well that is screened across the entire landfill depth due to the greater water column head and a potential preferential flow to the leachate collection system (LCS). A cluster of three wells screened at different depths, therefore, was considered over a single fully screened well. A detailed description of the site and the bioreact or can be found elsewhere (J ain et al. 2005). Jain et al. 2005 evaluated the performance of vertical wells for landfill leachate recirculation and found that the depth at which the leachate is injected into the vertical wells is one of the important factors dictating the amount of leachate added to the waste. Injection trials conducted found surface seeps to occur around the injection wells if liquids were added at a hydrostatic head above the surface of the landfill. A large number of vertical wells penetrating the surface geomembr ane contributed to air intrusion into the gas collection system which reduced the efficiency of the gas collection system. Differential settlement was observed around the vertical clusters due to leachate addition resulting in uneven surface of the landfil l at the end

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30 of the bioreactor operation. Also recirculating leachate at a constant pressure below the surface of the landfill required constant monitoring of the system and check for seeps. This research evaluated the performance of a unique method for ad ding leachate in the landfill by burying the vertical wells in an attempt to solve some of the limitations associated with vertical wells. The main objective of this research was to inject leachate in these buried vertical wells at a pressure higher than t he screen length of the vertical well without causing surface seeps on the landfill. Data on the flow rate, the associated pressure and the impact of the depth in response to leachate recirculation are presented. The flow rates of the buried vertical wells were compared with conventional vertical wells to evaluate the performance this method. 2.2 Materials and Methods 2.2.1 Site Description The experimental setup was built on Cell 4 and part of Cell 2 at the New River Regional Landfill located in Union County, Florida. The NRRL receives approximately 1000 metric tons per day of waste consisting of mixed residential and commercial waste. The landfill currently consists of five contiguous lined class I landfill cells totaling approximately 30 hectares, as s hown in Figure 21. Cell 4 and Cell 2 are approximately 7.8 and 3.6 hectares respectively in area and both these cells are equipped with a double liner system. The average height of the waste from the surface of the landfill to the leachate collection sys tem at the time of construction was approximately 21 m. The density of the landfilled waste was approximated to be 710 kg/m3. A clayey sandy soil mined on site was used as daily cover. Leachate recirculation was permitted in cell 2 and cell 4 at the time o f operation; however the maximum permitted amount of leachate recirculated in cell 4 and cell 2 was 122 m3 and 132.6 m3 per day respectively.

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31 2.2.2 Concept of Buried Vertical Well Clusters The buried vertical well clusters were built based on the following design criteria. The buried vertical wells should have the ability to add leachate at a pressure higher than the screen length of the vertical well without causing surface seeps on the landfill. Fewer pipes should penetrate through the side slope of the l andfill and connect to the vertical wells for easier maintenance of the landfill. The buried vertical wells should withstand uneven settlement of waste over time due to decomposition of waste and over burden pressure of the leachate injected. In this metho d of leachate recirculation, several vertical wells are drilled uniformly on the surface of a landfill before placing the final lift of waste on the landfill. These vertical wells are then grouped into several clusters. The vertical wells in each cluster a re connected to a single lateral leachate recirculation line via manifold system. This lateral leachate recirculation line extends all the way to the side slope of the landfill and is connected to the main leachate recirculation system of the landfill. Ano ther lift of waste is then placed on top of these vertical well clusters. To account for the uneven settlement of waste in the landfill over time, the slotted pipe in the vertical wells is not directly connected to the lateral leachate recirculation line via manifold system. Instead the manifold system extend s by a couple of feet into the vertical well so that the slotted pipe barely overlaps the manifold system as shown in Figure 2 2. When the settlement occurs in the landfill, the slotted pipe can furthe r slides inside the manifold system and prevent it damaging. The buried vertical well clusters have a number of potential advantages over conventional vertical wells. Large quantities of leachate can be injected under pressure in buried vertical well clus ters in a relatively shorter period of time compared to conventional vertical wells without causing surface seeps on the landfill. More waste can be placed on top of the landfill without

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32 dismantling the system. Fewer pipes penetrate through the side slope of the landfill compared to the number of buried vertical wells making it easy to maintain the landfill. The buried vertical wells also have a few disadvantages. The buried vertical wells cannot be repaired or fixed after installation due to potential dama ged caused to the pipes due to the over burden pressure of the waste on top of the buried vertical wells or uneven settlement of waste over a period of time due to leachate addition. There is potential for seeps over time if the pressure head of the leacha te injected is higher than the well depth and the thickness of waste on top of the vertical well clusters. 2.2.3 Experimental Set u p and Construction of the Buried Vertical Well Clusters The ex perimental set up consisted of six buried vertical well cluste rs located at a distance of 30m away from each other (except for one cluster that was located at a distance of 23 m away from the other cluster) as shown in Figure 2 3. The six well clusters were group into two sections; I and II. Each section had three we ll clusters of depths of 6, 9 and 12 m respectively as shown in Figure 2 4. Each clusters had 9 vertical wells located at a distance of 15 m away from each other within the cluster. All the nine wells in each cluster were connected to a single lateral leachate recirculation line via manifold system. This lateral leachate recirculation extended to the side slope of the landfill and was connected to the main leachate recirculation system of the landfill as shown in Figure 2 3. In this chapter the first and the last vertical well in a vertical well cluster is defined as the vertical wells closest and farthest to the lateral leachate recirculation line. Two vibrating wire (VW) piezometers (Model: 4500 S Geokon Inc.), placed on the bottom of the first and the l ast vertical well as shown in Figure 23 were used to measure the pressure and temperature of the leachate injected in the buried vertical well clusters. Two T type thermocouple wires ( PVC/PVC Ripcord, Type T, # 24 AWG, Nanmac Corporation), placed on the bottom of two other vertical wells as shown in Figure 2 3 were used to meas ure temperature

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33 in the other locations of the well cluster The 12 VW piezometers and 12 thermocouple wires were connected to a Campbell Scientific (CR10X) data logger using two multiplexers. Multilogger software (Canary system) was used to program the CR10X data logger to measure and record data at regular intervals. The frequency of data collection was initially set at every hour and then reset to every 10 minutes just before re c irculating leachate in the buried vertical well clusters for the first time. The multilogger software converted the pressure measured in digits into units of pressure by using the ABC factors and equation given in the geokon calibration sheets for each VW piezometer. A pressure transducer, pressure gauge, flow meter and globe valve were attached to the lateral leachate recirculation lines on the side slope of the landfill as shown in Figure 2 3. The leachate injection pressure was measured using a 0 20 mA pressure transducer (GE Druck, Connecticut, U.S.) and read using a loop calibrator (UPS II, GE Druck Inc.). A (030 psi Omega) pressure gauge was also connected for the same purpose. The flow rate and cumulative volume of leachate injected in the buried ve rtical wells clusters were measured using th e SeaMetrics IP80 flow meters (C ontrol ware house, Ocala ) The globe valves were used to control the flow rate of leachate injected in every cluster. Construction of the experimental set up began in summer 2006 on cell 4 at the NRRL. The vertical well clusters were installed inside a 0.75 1m deep trench using a hydraulic excavator (385C L caterpillar) and then back filled with waste to protect the pipes from getting damaged due to placement of waste and movement o f compactors on top of the buried vertical well clusters. A solid stem open flight auger with a diameter of 11.5 cm, attached to the drilling rig was used for drilling the boreholes as shown in Figure A 1 of Appendix A. A pointed tail bit was attached to the bottom of the solid stem open flight auger as shown in Figure A 2 of Appendix

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34 A. A temporary HDPE pipe was inserted inside the well after drilling. A slotted PVC pipe of diameter 5 cm was then inserted into the well through the HDPE pipe as shown in Fi gure A 3 of Appendix A. A cap was placed on the temporary HDPE pipe and the drilling rig was moved to the next well location until all the wells in a cluster were drilled. Customized HDPE manifold assembl y was made for every well based on its location to c onnect the vertical wells to the lateral leachate injection line. The temporary pipes were removed from the verticals wells and its respective manifold assembly was placed inside the vertical well as shown in Figure A 4 of Appendix A. These manifold assemblies were welded in situ using heat infusion welding to the lateral leachate recirculation line (SDR 17 HDPE, 7.6 cm diameter), that extended all the way to the side slope of the landfill. This lateral leachate recirculation line was connected to the main leachate recirculation system of the landfill. The VW piezometers and thermocouple wires were placed inside the bottom of the vertical wells by drilling 1 inch hole on top of the vertical well manifold assembly. The VW piezometers and the thermocouple wir es were then dropped through the hole in its respective wells, until it hit the bottom of the well. The hole was then plugged using an epoxy resin. The VW piezometer and the thermocouple wires were extended all the way to the side slope of the landfill and connected to the datalogger as shown in Figure A 5. The trenches were then back filled with waste. A layer of around three meters of waste then placed to bury the vertical well clusters. 2.2.4 System Operation and Monitoring Leachate recirculation was car ried out in all the six vertical well cluster s and operated for a period of 153 days. The leachate generated in all the cells at this site was used for leachate recirculation. Groundwater was used as a supplemental source of moisture if enough leachate was not available. The leachat e recirculation in the well clusters was intermittently operated for the first 105 days during the operating hours of the facility (8:00 AM to 5:00 PM) and closely

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35 monitored for operational constraints. Based on the experience gained from operating the well clusters, the system was then operated continuously (24 hours a day, seven days a week) for a period of 48 days with occasional intervals. The data logger recorded leachate pressure and temperature at the bottom of the vert ical wells continuously from all the 12 VW piezometers and 12 thermocoupl es and are annexed in appendix B The time of operation, cumulative flow rate, flow rate and pressure of leachate recirculation were recorded every hour m anually for all the six well clusters during the entire leachate recirculation period. The leachate injection pressure in this chapter is defined as the pressure of leachate just before it enters in the first vertical well in a cluster. This pressure was calculated by subtracting the pressure due to elevation difference between the top of a vertical well and the corresponding pressure gauge in the lateral leachate line and also the frictional loss due to pipe flow as shown in Appendix C A total of 80120 m3 (20,000 to 32,000 gallons) of leachate were added per day in all the well clusters. The leachate injection pressures were maintained at 4 8 m of water column. T he flow rates were maintained at 39 104m3/s per well cluster so that the total volume of leachate injected per day does not exceed the permit limit of 32,000 gallons. 2.3 Results and Discussion 2.3.1 Overall Performance A cumulative volume of 8,431 m3 (2.2 million gallons) of leachate was recirculated intermittently in all six buried vertical well clusters over a period o f 153 days. Table 21 shows the well depth, screen length, cumulative volume of leachate injected, total hours of operation, average flow rate, average leachate injection pressure and the average hydrostatic head at the bottom of the first vertical well in all the six buried vertical well clusters. A total of 1400 2300 m3 of leachate was added per vertical well clusters in four vertical well clusters. H owever only 115 and 362 m3 of leachate was added in the remaining two vertical well clusters respectively

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36 The average flow rate of leachate in the 6 m deep vertical well cluster in section II was only around 35% as compared to the other 6m deep well cluster in section I at similar operating pressures indicating a restricted flow in that cluster. This may b e due to a kink in the lateral leachate recirculation line of the cluster The 9m deep vertical well cluster in section II immediately started leaking leachate from the lateral recirculation line buried in the side slope of the landfill during leachate re circulation. This cluster was shut down for an extended period of time to repair the leak. Hence the 6m and the 9 m deep vertical well clusters in section II were not used for the interpretation of results. Results shown in Table 21 indicate that the lea chate recirculated in the buried vertical well clusters of section I had an average flow rates of 6.266.91 x 104 m3/sec at a lateral injection pressure of 6.136.39 m of water column (w.c.) in the vertical well clusters. The average flow rates of leach ate recirculated increased slightly with the depth of the vertical well clusters at similar operating pr essure. The surface of cell 4 was checked frequently for seeps. No seeps were found either on the surface or the side slope of cell 2 and cell 4 during the leachate recirculation period. The lateral leachate recirculation lines on the side slope of the landfill leaked leachate at the pipe joints few times during operating period. It was difficult to properly weld the SDR 17 HDPE pipes in situ on the side slope of the landfill due to smaller thickness of the pipe Hence a thicker SDR 11 HDPE pipes are recommended for future construction work. Only 3 out of 12 thermocouples and 8 out of 12 VW piezometer that were placed in the vertical well cluster and buried in the landfill worked properly. It was observed in the past as well that not all geotechnical instruments buried inside the landfill have worked properly due to the na ture of the waste (Jonnalagadda 2004; Jain 2005; Larson 2007). Since the wires of t hese

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37 instruments were directly buried in the waste, it is recommended to pass these wires though conduit pipes to prevent them from damage 2.3.2 Performance of a Vertical Well Cluster A 6 m deep buried vertical well cluster from section I was chosen to i llustrate the performance of a typical buried vertical well cluster. A cumulative volume of 1 ,806 m3 of leachate was added in 802 hours of intermittent leachate injection over a period of 153 days as shown in Table 21. The average flow rate of leachate re circulated in this vertical well cluster was 6.26 x 104 m3/sec (9.92 gpm) at an average leachate injection pressure of 6.39 m of w.c. (21 ft of w.c.). Figure 25 presents the c hange in pressure and temperature at the bottom of the first vertical well in the cluster during the initial days of leachate recirculation. Results indicate that as soon as the leachate recirculation was started the piezometer quickly attained the leachate pressure and temperature compared to the gradual decrease in pressure and t emperature when the leachate recirculation was stopped. On the 2nd day of operation, the hydrostatic head at the bottom of the well was 7.2 m of w.c, indicating that leachate was injected at a pressure higher than the screen length (6 m depth) of the verti cal well. Figure 2 7 presents the change in hydrostatic head and temperature in the first vertical well of the cluster over time. The graph indicates that the leachate was constantly injected at a pressure higher than the screen length of the vertical well for at least one vertical well in a cluster during the entire period of leachate recirculation. Figure 2 7 presents the change in hydrostatic head in the first and the last vertical wells of the cluster during leachate recirculation over time. Results in dicate that the pressure in the last vertical well was significant ly lower than the first vertical well Also the entire screen length in the last vertical well was not getting utilized during the initial 100 days of leachate recirculation.

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38 Since the first vertical well was closest to the leachate recirculation line, the first vertical well received more leachate and was subjected to a higher leachate injection pressure compared to the last vertical well. Also, the pressure loss between first and last vertical well might be due to the back pressures exerted by the landfill gas that would be present in the vertical wells. However, as the time progressed, the pressure at the bottom of the wells was almost the same except when leachate recirculation system was running. This suggests that the leachate was getting distributed in all the vertical wells of a cluster. Figure 28 presents that change in flow rate per unit leachate injection pressure head over time. The graph indicates that the flow rate decreased ove r time due to a reduction in the hydraulic gradient with volume of liquids added. The hydraulic gradient reduces due to an increase in the flow path length of the leachate as the zone of impact increases. The flow rate of leachate recirculated attains a st eady state value when the lateral extent of the liquids movement approach as steady state value (Townsend et al. 2006). Using the design charts of vertical well system for liquids addition at bioreactor landfills created by Townsend et al. (2006), it was determined that a leachate volume of 25155m3 was needed for the 6 m deep buried vertical well cluster to reach a steady state condition assuming an anisotropy of 20 and a drainable porosity of 0.5. 2.3.3 Comparison of two Buried Vertical Well Clusters With the Same Depth To compare the performance of two vertical well clusters with same depth, 12 m deep buried vertical wells clusters from section I and section II were chosen. Leachate recirculation was carried intermittently over a period of 80 days in both the well clusters and operated at similar leachate injection pressure of 6 7 m of w.c.. A total of 1,100 m3 of leachate was added in the vertical well cluster of section I as compared to only 730 m3 of leachate added in the vertical

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39 well cluster of Sectio n II. Also the average leachate recirculation flow rate was 14.8 104 m3/sec in section I compared to only 8.64104 m3/sec in section II. Figure 29 presents the change in flow rate of leachate added at various leachate injection pressures between 12 m deep vertical well clusters of section I and section II. Results indicate that at a constant pressure, the flow rate of leachate injected was higher in section I compared to section II. The loss in flow rate in section II well clusters might be caused by a kink in the lateral leachate injection line or broken joints between the pipes due to over burden pressure of the waste above of the well clusters. Hence, it is again suggested to use thicker HDPE pipes such as SDR 11 for future construction work. Figure 210 presents the change in hydrostatic head in the first vertical well between two 12 m deep vertical well clusters over cumulative volume of leachate added. The hydrostatic head increased linearly with cumulative volume of leachate added indicating similar performance of both the well clusters. The minor difference of around 2 m of w.c in the hydrostatic head between the two clusters might be due to the heterogeneous nature of the waste. 2.3.4 Impact of Well Depth on the Performance of the Vertical Well Clusters T he vertical well clusters of different depths were compared to determine the impact of the depth on the performance of vertical well clusters. Since the flow rate of leachate injected depends on the volume of leachate added in the waste, three vertical well clusters of section I of different depths were compared after injecting 1000m3 of leachate. Table 22 provides the well depths, screen length, hours of operation, average flow rate, average leachate injection pressure, and the flow rates per unit screen length for the vertical well clusters. The average flow rate varied substantially from 9.3104 to 14.2104m3/sec (14.7 to 22.5 gpm) with increase in the well depth of the ver tical well cluster from 6 to 9m. H owever the flow rates between 9m an d 12m deep vertical well clusters did not vary substantially. This could be due to two reasons. The

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40 permeability of the waste is lower with increase in the depth of the landfill as shown in chapter 3. Also, not all the screen length in the individual verti cal wells of the cluster might have been utilized during the initial period of leachate recirculation as evident from the 6m deep well cluster. The flow rate per unit screen length decreased with increase in the depth of the landfill as shown in Table 22. The substantial difference in the flow rate per unit screen length between 9m and 12m compared to the 6m and 9m deep well cluster suggest that higher screen length was not getting utilized in the 12m deep well cluster. Figure 211 presents change in pre ssure due to leachate recirculation at the bottom of the first vertical well in three vertical well clusters over time. The graphs indicate that leachate was recirculated under a pressure higher than the screen length of the vertical well in all the three vertical well clusters. The leachate level gradually rose in all the vertical well clusters with time. After stopping leachate recirculation it was observed that hydrostatic head of the leachate in the wells was higher with increase in the well depth of th e landfill. This may be due to a lower permeability of the waste in deeper sections of the landfill (Jain et al. 2005b) which causes the surrounding waste to saturate quickly compared to the shallow sections of the landfill. To further understand the impac t of depth on the performance of the vertical well clusters, leachate was injected at various pressures and its corresponding flow rates were measured. Figure 212 indicates that the flow rates of leachate injected did not vary significantly with the well depth of the vertical well clusters at various leachate injection pressures. For example, at a leachate injection pressure of 5m of w.c, the flow rates were 10.5x 104 and 11.5 x 104 m3/ sec (16.6 and 18.2 gpm) for 6m and 12 m deep vertical well cluster respectively. This is due to the

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41 fact the leachate recirculation in the vertical well clusters have not reached a steady state as shown earlier for the 6m deep vertical well cluster. 2.3.5 Comparison of Field Test Results of Buried Vertical Wells with Conv entional Vertical Wells Field test results of the buried vertical well clusters were compared with the field test results of a conventional vertical well conducted by Jain 2005 as shown in Table 23. Since a layer of waste was placed on top of the vertical well clusters, the well depth from the surface of the landfill was higher than the actual length of the vertical well clusters inside the waste. Results indicated that substantial amount of leachate was added in the well clusters compared to individual v ertical wells in the same period of time. The average leachate flow rate per unit screen length of the buried vertical well clusters was almost the same or higher compared to the conventional vertical wells. The flow rate per unit screen length of the vert ical well clusters were lower than the 6m deep vertical well, but higher than the 16.2 and 18 m deep vertical well. The higher flow rate in the 6m deep vertical well might be due to the lower permeability of waste in the shallow sections of the landfill. A lso, not all the screen length in the individual vertical wells of the cluster might have been utilized during the initial period of leachate recirculation. 2.3.6 Assessment of Technology A cumulative volume of 8431 m3 (2.2 million gallons) of leachate wa s recirculated intermittently in the buried vertical well clusters over the period of 153 days without causing any surface seeps on the landfill. Of the six buried vertical well clusters only one buried vertical well cluster had a lower leachate injection rate compared to the others and was not fixable due to a restricted flow between the lateral leachate recirculation line and the vertical wells in the cluster. The average flow rate varied substantially from 9.3104 to 14.2104m3/sec (14.7 to 22.5 gpm)

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42 with increase in the well depth of the vertical well cluster from 6 to 9m. Leachate was injected under a pressure of 6.136.39 m of w.c. in the buried vertical well clusters without causing any surface seeps on the landfill. Since there was significant red uction in pressures between the first and the last vertical well in the cluster during leachate recirculation, not all the available screen length was getting used during the initial period of leachate re circulation However, as the time progressed, the p ressure at the bottom of the wells was almost the same except when leachate recirculation system was running. This suggests that the leachate was eventually getting distributed in all the vertical wells of a cluster. Comparison of field test results of Ja in, 2005 indicated that the average leachate flow rate per unit screen length of the buried vertical well clusters was almost the same or higher compared to the conventional vertical wells. However the biggest advantage of using this method is that constan t monitoring of the leachate recirculation system was not required and the ability to inject leachate in the buried vertical wells at a pressure higher than the screen length of the vertical well without causing surface seeps on the landfill Also, the mai ntenance of the landfill was easier as fewer leachate injection lines penetrated from the side slope of the landfill. Due to occasional leaks on leachate injection lines on the side slope of the landfill and possible kinks inside the lateral leachate inje ction lines, it is recommended to use a thicker HDPE pipe such as SDR 11 for future applications.

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43 Figure 21. Plan view of various cells and the leachate recirculation system at the NRRL

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44 Due to settlement of the landfill Lift of waste on top of the buried vertical wells HDPE pipe Slotted PVC pipe Initial length of the slotted pipe Final length of the slotted pipe Surface of the landfill Surface of the landfillBefore Settlement After SettlementChange in elevation Figure 2 2. Cross section of a buried well before and due to settlement Figure 2 3. Plan view of the modified vertical well clusters in cell 4 at NRRL Leachate recirculation lines

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45 Figure 2 4. Cross section view of the modified vertical well clusters in cell 4 at NRRL Days 0 5 10 15 20 Pressure (m of H 2 0) 0 2 4 6 8 10 12 14 Temperature (C) 20 30 40 50 Pressure Temperature Figure 25. Change in pressure and temperature at the bottom of t he first vertical well of a 6 m deep vertical well cluster during the initial days of leachate recirculation

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46 Days 0 20 40 60 80 100 120 140 160 Pressure (m of H 2 0) 0 5 10 15 20 25 30 Temperature (C) -20 0 20 40 60 Pressure (6m deep cluster) Temperature (6m deep cluster) Figure 26. Change in pressure and temperature at the bottom of the first vertical well of a 6 m deep vertical well cluster over time Day 1 = 7-30-08 0 20 40 60 80 100 120 140 160 Pressure at the bottom of the well (m of w.c. ) 0 5 10 15 20 20 m (first well) 20 m (last well) 1 to 165 = 11/1/08 to 4/25/09 Figure 27. Change in pressure at the bottom of the first and the last vertical well in a 6 m deep vertical well cluster due to the leachate recirculation over time (Day 1 to 165 = 11/1/08 to 4/25/09)

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47 Days 0 20 40 60 80 100 120 140 Flow rate per unit leachate injection pressure x 10 -5 (m 2 /sec) 0 5 10 15 20 25 30 35 Figure 28. Change in flow rate per unit leachate injection p ressure over time Leachate injection pressure (m of w.c.) 0 2 4 6 8 10 12 Flowrate (x 10 -4 m 3 /sec) 0 2 4 6 8 10 12 14 12 m deep (Section II) 12 m deep (Section I) Figure 29. Change in flow rate of leachate added at various leachate injection pressures between 12 m deep vertical well clusters of section I and section II

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48 Cumulativ volume of leachate added (m 3 ) 0 200 400 600 800 1000 Pressure (m of w.c.) 0 2 4 6 8 10 12 14 16 12m deep cluster (Section II) 12m deep cluster (Section I) Figure 210. Change in hydrostatic pressure in the first vertical well be tween two 12 m deep vertical well clusters over cumulative volume of leachate added

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49 90 to 260 = 10/28/08 to 4/16/09 0 20 40 60 80 100 120 140 160 Pressure (m of w.c. ) 0 2 4 6 8 10 12 14 6 m deep well cluster 0 20 40 60 80 100 120 140 160 Pressure (m of w.c. ) 0 2 4 6 8 10 12 14 16 9 m deep well cluster Days 0 20 40 60 80 100 120 140 160 Pressure (m of w.c. ) 0 2 4 6 8 10 12 14 16 12 m deep well cluster Day 1 = 11-11-08 Figure 211. Change in pressure due to leachate recirculation at the bottom of the first vertical well in 6 m, 9m and 12m deep vertical well clusters over time

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50 Pressure (m of water column) 0 2 4 6 8 Flowrate (x 10-4 m3/sec) 0 2 4 6 8 10 12 14 6 m deep vertical well cluster 9 m deep vertical well cluster 12 m deep vertical well cluster 6m depth 12m depth 9m depth F igure 212. Change in flow rate at various leachate injection pressures in 6, 9 and 12 m deep vertical well clusters

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51 Table 2 1. Field injection test result of buried vertical wells clusters Section Name of the cluster Depth of well cluster Screen lengt h Total volume of leachate added Total hours of operation Average flow rate Average leachate injection pressure Average pressure at the bottom of the first vertical well in a cluster (m) (m) (m3) (hr) (x 10 4 m3/sec) (m of w.c.) (m of w.c.) I F 12 10.7 2389.39 960 6.91 6.133.1 7.334.69 I D 9 7.6 2295.1 957 6.66 6.133.4 6.014.93 I B 6 4.6 1806.44 802 6.26 6.394.2 4.943.69 II E 12 10.7 1462.35 556 7.31 7.543.15 2.792.28 II C 9 7.6 362.404 101 9.97 1.583.75 II A 6 4.6 115.326 147 2.18 5.23.5 1.681.28 Table 22. Comparison of field test results of buried vertical well clusters with different depths Type of vertical well Well depth (m) Screen length (m) Total volume injected (m 3 ) Total hours of injection Average flow rate (x 104 m3/s) Average leachate injection pressure (m of w.c.) Flow rate per unit screen length (x 105 m3/s m2) Vertical well cluster 6 4.6 1068.7 317.9 9.3 6.394.2 2.2 Vertical well cluster 9 7.6 1051.9 205.7 14.2 6.133.4 2.1 Vertical well cluster 12 10.7 1022.7 1 86.7 15.2 6.133.1 1.6

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52 Table 23. Comparison of field test results of buried vertical well clusters with vertical wells Type of vertical well Well depth from surface of the landfill (m) Screen length (m) Total volume injected (m3) Total hours of injec tion Average flowrate per vertical well (x 10-4 m3/sec) Flowrate per unit screen length (x 10-5 m3/sec m) Vertical well 6.1 3.05 118 313 1.0 3.3 Vertical well 16.2 6.1 151 364 1.1 1.8 Vertical well 18 6.1 97 364 0.7 1.1 Vertical well cluster 11 4.6 1068.7 317.9 1.0 2.2 Vertical well cluster 14 7.6 1051.9 205.7 1.6 2.1 Vertical well cluster 17 10.7 1022.7 186.7 1.7 1.6

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53 CHAPTER 3 TEMPORAL AND SPATIAL PORE WATER PRESSURE DISTRIBUTION SURROUNDING VERTICAL LANDFILL LE ACHATE RECIRCULATION WELL 3.1 Int roduction Modern engineered landfills have evolved from conventional dry tomb landfills to highly engineered containment system s designed to minimize the impact of municipal solid waste (MSW) on the environment and human health. For over a decade now, bioreactor technology has received much attention as it changes the goal of landfilling from storage of waste to treatment of waste. The addition of leachate is one of the important and cost effective methods that provide control and process optimization in the operation of a bioreactor landfil l (Townsend et al. 1995; Reinha rt et al. 1996; Reinhart and Townsend 1997). Several full scale bioreactors have been operational in the United States (Townsend et al. 1995; Hudgins et al. 2000, Smith et al 2000; Jain et al 2005; C.H. Benson et al. 2007; Larson 2007). The accelerated decomposition of refuse in bioreactor landfills considerably changes the geotechnical characteristics of the waste in the landfill, and thereby increases the concern for waste stability ( Hossain et al. 2009). An increase in the hydrostatic pressure of water in the interstitial spaces of the waste and cover soil (referred to as pore water pressure ) decreases the effective stress between waste and soil particles, which in turns leads to a de crease in the shear strength of the waste mass (Koerner et al. 2000). A reduction in shear strength can in some circumstances lead to a slope failure. The catastrophic slope failure of the Dona Juana Landfill (Hendron et al. 1999; Gonzalez Garcia and Espi nosa Silva 2003) showed that the design and analysis methods established for dry landfills where pore pressures within the waste are not considered may not be appropriate for wet or bioreactor landfills. Koerner and Soong (2000) have addressed the influenc e of leachate on the stability of the waste mass by calculating the factor of safety using the pore leachate pressure in the waste.

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54 Several mathematical models have been developed to simulate the impact of leachate addition in the waste using vertical wells (McCreanor et al. 1996; Khire et al. 2006; Jain et al. 2007). Simulation results of Jain et al. (2007) indicated that even though large pore pressure existed near the well during leachate addition, that pressure dissipated within a smaller radial distan ce from the well and that the anisotropic ratio had a significant impact on the lateral extent of moisture distribution. Although, a mathematical model gives us useful information on impact of leachate recirculation into vertical wells, very little is kno wn about the pressures that actually develop within full scale MSW landfills as a result of added leachate. The objective of the research in this chapter i s to examine the temporal and spatial impact of leachate recirculation into buried vertical wells on the pore water pressure in the surrounding waste in a full scale MSW landfill. This chapter reports experiences of leachate addition in a buried vertical well surrounded by multiple VW piezometers over a duration time. Data on lateral and vertical impact o n pore water pressure in the surrounding waste in response to cumulative volume of leachate added, and associated leachate injection pressure and operation period, are presented. For this research multilevel vibrating wire (VW) piezometer s were used to measure pore pressure in the landfill and installed using the groutedin method. VW piezometers have been used in the past for measuring pore pressure for landfill applications (Simoni et al. 2004; Hayder et al. 2007), however, these piezometers were us ed either at shallow depths to measure pore pressure on an unstable clay slope or to monitor leachate pressure injected in the permeable blankets of a landfill. VW piezometers contain thermistors to measure temperature. The effect of the liquid injection o n the temperature inside the landfill has been studied (Kumar et al. 2007) and the results indicate that when leachate or groundwater at temperature lower than the

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55 landfilled waste is injected into the landfill, it has an initial cooling effect on the waste, until the biological activity, enhanced by the additional moisture, releases heat. A multilevel VW piezometer using the grouted in installation method is typically used to measure pore water pressure in saturated media, but the waste in a landfill is generally unsaturated. A crucial parameter for the success of the fully grouted method is the permeability of the cement bentonite grout (Contreras et al. 2008). Grout is a highly porous solid with a low permeability that lies somewhere in the cement and bentonite range, from 1x105 to 1x109 cm/sec. Hence there is a time lag associated with the liquids movements in an unsaturated grout. Thus, an additional experiment was conducted in the lab to determine hydrodynamic lag time in reading the pore water pressure by the VW piezometer encased in grout due to transition from unsaturated to saturated state of grout Details of this experiment are shown in appendix E. 3.2 Materials and Methods 3.2.1 Site Description The experimental setup was built on Cell 4 at t he New River Regional Landfill located in Union County, Florida as shown in Figure 31. The NRRL receives 1000 metric tons per day of waste consisting of mixed residential and commercial waste. The landfill currently consists of five class I contiguous lined landfill cells totaling approximately 30 hectares. Cell 4 is approximately 7.8 hectares in area and is equipped with a double liner system. The average height of the waste from the surface of the landfill to the leachate collection system at the time of construction was approximately 21 m. The density of the landfilled waste was approximated to be 710 kg/m3. A clayey sandy soil mined on site was used as daily cover. Leachate recirculation was permitted in cell 4 at the time of operation; however the maximum amount of leachate recirculated was 122 m3 per day.

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56 3.2.2 Experiment Set up and Construction The experimental set up consisted of two 12.2 m deep buried vertical wells, situated 7.6 m away from each other as shown in Figure s 3 2 and 33. Each of th ese buried vertical wells was connected to their respective lateral leachate recirculation line that extended to the side slope of the landfill and connected to the main leachate recirculation system. Surrounding these two buried vertical wells were18 multi level piezometers (Model: 52611199 Slope indicator), placed 1.5 m away from each other as shown in Figure 32. Each multi level piezometer had five VW piezometers, placed three meters apart from each other and was 15.2 m in length as shown in Figure 33. The whole multi level piezometer assembly was placed inside a 20 cm diameter borehole and enclosed in grout. Another lift of waste was placed on top of this experimental set up to bury the vertical wells and the multilevel piezometer wells. All the piezom eters were connected a datalogger (CR10X Slope indicator) to measure and record pore pressure and temperature spatially from the buried vertical wells in the surrounding waste. A pressure transducer, pressure gauge, flow meter and globe valve were attach ed to both the lateral leachate recirculation lines on the side slope of the landfill as shown in Figure 32. The leachate injection pressure was measured using a 0 20 mA pressure transducer (GE Druck, Connecticut, U.S.) and read using a loop calibrator (U PS II, GE Druck Inc.). A (030 psi Omega) pressure gauge was also connected to measure leachate injection pressure. The flow rate and cumulative volume of leachate injected in the buried vertical wells were measured using the SeaMetrics IP80 flow meters ( control ware house, Ocala. The globe valves were used to control the flow rate of leachate injected in a vertical well. Construction of the experimental set up began in summer 2006 and was built in the north end of Cell 4 at the NRRL. The two main buried v ertical wells were drilled using a solid stem open flight auger which had a diameter of 12 cm. After drilling, a slotted schedule 40 PVC pipe

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57 was inserted inside the borehole. The slotted PVC pipe was 15 m in length and 5 cm in diameter. The slotted PVC pi pe was connected to a lateral 7.6 cm diameter HDPE pipe via manifold system. The lateral HDPE pipe extended to the side slope of the landfill and was connected to the main leachate injections system. A hollow stem open flight auger was used for drilling 20 cm diameter boreholes to install the multilevel VW piezometer assembly as shown in Appendix D 1. Initial readings of all the piezometers were taken before assembling the multilevel VW piezometers. To assemble the multilevel VW piezometers, three sched ule 40 PVC pipes and two piezometers were glued together in an alternate fashion using a clear coat PVC glue to make a part of the multilevel VW piezometer assembly as shown in Appendix D 2. Then, this assembly was placed inside the borehole using a crane attached to the dri lling rig as shown in Appendix D 3. Once this assembly was placed inside the well, the wires of this assembly were snaked through another set of PVC pipe and piezometer assembly. Both these assemblies were then glued in situ and lowere d further in the well. This process was repeated until the entire multilevel VW piezometer assembly was placed inside the bore hole. The bore hole was then filled with grout using a grout machine built by ChemGrout, Illinois as shown in Appendix D 4. Grout w as prepared using a ratio of 1 : 2.5 : 0.5 for portland cement : water : bentonite respectively. 3.2.3 System Operation and Monitoring Leachate was only recirculated in the main buried vertical well intermittently for a period of 122 days The system was operated for the first two months primarily during the operating hours of the facility (8:00 AM to 5:00 PM) and closely monitored for operational constraints. The system was then operated continuously (24/7) for several days. Even after stopping the le achate injections, the pore pressures in the surrounding waste were still being monitored continuously. The time of operation, cumulative volume flowrate and pressure was recorded every hour manually during the leachate recirculation period. The pore pres sures realized by the

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58 VW piezometers were measured initially using the hand held data recorder (slope indicator) for the first few months before connecting the VW piezometers to the datalogger. The data logger recorded the pore pressure continuously from all the 90 VW piezometers in an interval of one hour. 1530 m3 of leachate were added daily during each operation period and the leachate injection pressure was maintained at a pressure 14 16 m of water column at the bottom of the buried vertical well and a flowrate of 1.1 1.5 103 m3/s. 3.2.4 Data Management Data from the 90 VW piezometers were downloaded from the datalogger using the LoggerNet 3.X software (Campbell Scientific Software). Pressure data were recorded in frequency (hz) and the temperature data were recorded in degree Celsius. The pore pressure data was converted from frequency (hz) into units of pressure by using the ABC factors and equation given in the slope indicator calibration sheets for each VW piezometer. An example of the sample calculation is shown in Appendix F. For easier interpretation of data, the date of calibration of the VW piezometers in the Geokon lab was considered as day one in the results section to see the change in pore pressures measured by the VW Piezometers with time. Some of the VW piezometers showed pore pressure as much as 6 8 m of w.c. before leachate injection. In order to see the impact of leachate injection into the buried vertical wells on the pore water pressure in the surrounding waste, the pore pressur es measured by all the VW piezometers were normalized in the results section and it was assumed that landfill gas pressure changed negligibly during the period of liquids injection. The pore pressure data for each VW piezometers were normalized by subtract ing its respective pore pressures just before injecting leachate for the first time. An example of how the data was normalized is shown in appendix F.

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59 3.3 Results and Discussion 3.3.1 Overall Sensor Performance A total of 58 out of the 90 piezometers worked properly. A total of 13 piezometers stopped working immediately after installation and 19 piezometers either stopped working or started giving highly erratic and fluctuating data during the course of two years. An example of a piezometer that was not co nsidered for interpretation of results due to highly erratic and fluctuating pore water pressure data is given in Appendix F. Most of the piezometers that did not work were located in t he deeper sections of the multi level piezometers assembly. Improper sp licing of the wires, clogged piezometer filter cap or broken wires due to excessive overburden pressure of the waste are possible reasons for the faulty readings The 58 piezometers responded to leachate injection by showing an increase in pore water pres sure in the surrounding waste There was an initial time lag of 1224 hours in reading the correct change in pore pressure due to the time taken to saturate the grout However, once the grout became saturated, the piezometers respond within one hour of le achate recirculation The pore pressures and the normalized por e pressure measured with time for the 58 working piezometers are shown in Appendix G Out of the 58 piezometers that read the pore pressures correctly, only 39 piezometers measured the temperature correctly. The temperatures were beyond the calibration range ( 20C to 80C) in the piezometers that did not work well as shown by some of the piezometers in appendix G. 3.3.2 Pore Pressures in the Waste before Leachate Recirculation Figure 3 4 presents the pore pressures measured by the piezometers at various depths in the landfill before leachate recirculation The pore pressures varied from 0.5 to 5 m of w.c. The initial high pore pressures in the waste are believed to be a result of landfill gas p ressure produced from the decomposition of organic waste (Berger et al. 2001). A one way ANOVA for

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60 0.05 level indicated that the pore pressure measured by the piezometers at various depth of the landfill [F(4,57) = 34.48, P = 1.08 1013] were different from each other and increased substantially with depth. Gas pressure s as high as 7 7.5 m of w.c. has not been reported in literature in a landfill. One possibility was that the high pore pressure could be due to the presence of the head in the gout encased piezometers Water was added initially to prepare t he gout mixture and poured in the piezometer wells. So an experiment was set up in the lab to determine the time taken by the water in the grout to dissipate in the surrounding sand media as mentioned in Appendix E It was found that the grout took around 22 days to full y dissipate the water in the surrounding sand media as shown in Appendix E 2. So, the high pore pressures were not due to the presence of water surrounding the piezometers. The other possibility was that the high pore pressures in the landfi ll could be due to the presence of landfill gas. Using the numerical model developed by Townsend et al. (2005), the pore pressure that developed due to landfill gas within a conventional landfill was estimated as shown in Appendix H. Results suggested that a lower permeability in the range of kz = 1013 m2 was required to cause such high gas pressures in the landfill. Air injection test conducted by Jain et al. (2005) at the NRRL landfill indicated that similar lower permeability of waste was found in the d eeper sections of the landfill. The fact that the pore pressures increases with increase in the depth of the landfill could be due a decrease in permeability with the depth of the landfill. 3.3.3 Hydrodynamic Lag Time in Reading the Pore Water Pressure by the Piezometer Encased i n Grout Table E 1 of appendix E indicates that the hydrodynamic lag time of 2448 hours associated with reading the correct pore water pressure measured by the piezometer encased in grout due to transition from unsaturated to satur ated state of grout due to liquids addition.

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61 However, once the surrounding grout gets saturated in water the hydrodynamic lag time varies from se conds to several minutes (McKenna 1995, Mikkelsen 2002, and Mikkelsen et al. 2003). The piezometer tips only r equire a small equalization volume (102 to 105 cm3) and the saturated grout can quickly transmit this volume over the short distance between the formation and the piezometer cavity (McKenna 1995). 3.3.4 Piezometer Responses in the Initial Period of Leach ate Re circulation Several piezometers were chosen as examples to illustrate the typical response during the initial days of operation. Leachate recirculation was first started on day 1313 and was carried out for 4 6 hours per day as indicated by the leachate injection pressure in Figure 3 5 and 3 6. The average flowrate was13.67104 m3/sec and the applied pressure at the bottom of the well were maintained at 13 17 m of w.c. during the leachate recirculation period Figures 3 5 (a), (b), (c) and (d) prese nt the piezometer responses to leachate recirculation at various depths of the landfill and at a fixed radial distance 1.5 m from the vertical well. Figure 3.5 (a) presents the pore pressure, temperature and leachate injection pressure of a piezometer located at depth of 5.8 m from the surface of the landfill. When the leachate recirculation was started on day 1313, the pore pressure increased and the temperature decreased after a lag time of 4 hour when the moisture front hit the piezometers. This lag time might be the time taken by the moisture to travel from the well to the piezometer. The temperature decreased for the next couple of days due to colder temperature of the moisture added, after which it reached a thermal equilibrium between the moisture an d the surrounding waste. The pore pressure increased marginally compared to the leachate injection pressure in the well but then quickly decreased within an hour in the first day of operation. In the second day, as soon as the leachate recirculation was st arted the pore pressure in the waste quickly increased within an hour as the

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62 waste was already partially saturated. When the leachate recirculation was stopped, the pressures in the waste did not drop right away, but slowly decreased with time. From Figur e 3 5 (b) it is observed that at a depth of 8.8m, the pore pressure increased gradually within 3 hours of leachate recirculation; however, the temperature did not decrease until the next day. This suggests that the initial increase in pore pressure without an increase in temperature might be due to compression of the landfill gas from the surrounding moisture front movement. In the second day of leachate recirculation, the temperature decreased along with an increase in the pore pressure indicating that the moisture front had reached the piezometer. From Figure 3 5 (c) and (d) it is observed that at deeper locations, the pore pressure increased gradually however the temperature did not decrease. This indicates that the moisture front might not have reached the piezometers. The piezometer responses shown above were the typical results for different depths for the remaining piezometers. The movement of the moisture front was mainly in the shallow section (5.8 and 8.8m depths) of the landfill compared to the deeper section (14.9 and 18 m depths) of the landfill during the initial days of operation. This might be due to a lower waste permeability in the deeper sections of the landfill. However, in certain locations the moisture front reached the middle sections of the landfill compared to the shallow sections as shown in appendix G. This could be due to preferential path of leachate due to the heterogeneous nature of the waste. Figure 36 (a) and (b) presents the piezometer responses to leachate recirculation i n radial direction from the vertical well and at a depth of 5.8m and 14.9 m from surface of the landfill during the initial days of operation. Results indicate that the pore pressures decreased with the radial distance from the well due to a decrease in hy draulic gradient.

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63 Based on temperature change as shown in appendix G, the graphs indicate that the water front had travelled only a radial distance of 3 m in the shallow sections of the landfill. In the deeper sections of the landfill, the pore pressures were mainly due to the landfill gas as the temperatures did not change at these locations. 3.3.5 Temporal Impact of Leachate Recirculation on the Pore Pressure in the Surrounding Waste A total of 1422 m3 (375,710 gallons) of leachate was re circulated inte rmittently in main buried vertical well for a period of 122 days The average flowrate of leachate recirculation was 13.33.6 104 m3/s (20.95.8 gpm) and the applied pressure at the bottom of the well was 15.382.4 m of w.c (50.58 ft of w.c.). Temperatu re data from appendix B indicates that the moisture front had wetted 88% of the piezometers; however, most of these wetted piezometers were located up to a radial distance of 2.2m from the well. One fourth of the piezometers located at a radial distance of 2.2 to 7.8 m from the vertical well were not wetted. T en piezometers were chosen to illustrate the temporal impact of liquid recirculation into buried vertical well on the pore water pressure in the surrounding waste Five piezometers were located at a radial distance of 2.2 m from the buried vertical well and at a depth of 5.8, 8.8, 11.9, 14.9 and 18m respectively from the surface of the landfill The remaining five piezometers were located at a radial distance of 6.3 m from the buried vertical well and a t a depth of 5.8, 8.8, 11.9, 14.9 and 18m respectively from the surface of the landfill. The Figures 3 7 show the change in pore water pressure of the piezometers and the leachate injection pressure on the bottom of the well over time. T he pore pressures i ncreased stead i ly to 26 m of w.c. over time in all ten piezometers indicating that the degree of saturation in the surrounding waste had increased due to leachate addition Using the design charts for liquids addition in a vertical well system

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64 developed b y Townsend et al. (2006), the total volume of leachate that needs to be added to the well to reach a steady state is 26,350 m3. This suggests that the pore water pressure will further increase in the surrounding waste with leachate addition as only a small quantity leachate was added in the vertical well compared to the volume to reach the steady state. The change in pore water pressure with time was higher in all the piezometer s that were located closed to the vertical well compared to the piezometers tha t were located away from the vertical well at the same depths. Th is decrease in pore water pressure in the radial direction from the vertical well during leachate recirculation is mainly due to a decrease in the hydraulic gradient The hydraulic gradient reduces due to an increase in the flow path length as the zone of impact increases 3.3.6 Spatial impact of leachate recirculation on the pore pressure in the surrounding waste Figures 3 8 and 39 present the results of spatial impact of leachate recircul ation into buried vertical well on the pore pressure in the surrounding waste. The change in pore pressures shown in these graphs are when the leachate was still being injected at a pressure of 20 m of w.c.at the bottom of the buried well and at a flow rat e of 6 x 104 m3/s A cumulative volume of 1400 m3 of leachate had been re circulated prior to that time. Figure 3 8 (a) presents the radial change in pore pressure from the buried vertical well at a depth of 5.8 m from the surface of the landfill. In this Figure the pressure at the bottom of the well is shown at a zero meter radial distance. Results indicate that the pressures in the waste are much less than the pressures in the well. For example, at a radial distance of 6 m away from the leachate injectio n well, the pore water pressure reduced by over 50 %. These results are in agreement with the simulations results carried out by Jain et al. (2007). The pore water pressure further reduces to 75% with increase in the depth of the landfill as shown in Figur es 3 8 (b) and (c). At a depth of 18m, which is 3 m below the bottom of the leachate injection well, change in

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65 pore pressure was significantly lower than the leachate injection pressure at the bottom of the well and was fairly constant in the radial direct ion away from the buried vertical well as shown in Figure 3 8 (d). This might be due to the lower permeability of waste in the deeper sections of the landfill along with the highly anisotropic nature of the waste. Figure 3 9 (a) presents the change in por e pressure at various depths from the surface of the landfill and a radial distance of 2.15 m away from the buried vertical well. Results indicate that, even though the hydrostatic head increased with the depth of the vertical well during leachate injectio n, the pore water pressure in the waste did not increase with proportionally This trend was similar even at farther locations from the vertical well as shown in Figure 4 9 (b), (c) and (d). This could be due to the decrease in permeability of waste in wit h an increase in the depth of the landfill. The permeability of the waste is inversely proportional to the pressure gradient as known from Darcys law. So, the even though the hydrostatic head in the well increased with the depth of the well, the pressure measured by the piezometers in the piezometer wells remained constant due to decrease in permeability of the waste with the depth of the landfill. At a radial distance of 2.15m from the buried vertical well as shown in Figure 39 (a), there is a significa nt difference in the pore water pressure in the waste at depth 14.9m and 18m from the surface of the well. Even though the injection pressure was the same and there was slight difference in the flow path of the leachate between the 14.9 m and 18m depth, there was a significant difference in the pore water pressures in the waste in these locations. This could be due to the anisotropic nature of the waste caused by the compaction method of waste in a landfill. This caused the water to travel more preferential ly in radial direction rather than in

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66 vertical direction. Hence the pore pressure in the waste at 18 m depth was lower than the 14.9 m depth. 3.3.7 Implications of This Research with Side Slope Stability Excess pore pressure is a very important parameter i n slope stability analysis of landfills. If leachate is injected along a potential failure plane, it increases pore water pressure which decreases the eff ective stress and proportionately decreases the shear strength. This can lead to mobilization of shea r deformation and ultimately to failure. Koerner and Soong (2000) have addressed the influence of leachate under excess pore pressure due to leachate recirculation on the stability of the waste mass in a landfill by calculating the factor of safety (FOS). The FOS is ratio of resisting and driving forces along the potential failure planes. Resisting forces consist of the shear strength of the waste, soil and/or geosynthetics through which the potential failure surface extends. The driving forces are the grav itational stresses of the waste, primarily the wedge or segment of waste behind the main body of waste. This research was conducted to give geotechnical engineers some guidelines on assuming a suitable value for excess pore pressures that develop in the s urrounding waste due to leachate addition. Since high landfill gas pressures were observed in the various sections of the landfill, the gas pressure has to be accounted for along the potential failure planes in the slope stability analysis. A lower value o f the gas pressures has to be assumed near the edge of the landfill compared to the inner sections of the landfill due to dissipation of gas along the side slope of the landfill. The bottom of the vertical well was located at least 50 m away from the side slope of the landfill. Even though large pressures were present in the bottom of a buried vertical well due to leachate addition, the water pressure dramatically declined at locations away from the well. The pressure in the well rapidly dissipated within the media. Hence, the shear strength of the waste

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67 along the radial direction would not reduce substantially at locations away from the vertical well. Also, there was a significant reduction in the pore water pressure in just few meters below the bottom of the buried vertical well. Hence, the shear strength will not decrease at most of the points along the slope of the potential failure planes. Thus, the factor of safety will not reduce substantially due to leachate addition. An important point that a geot echnical engineers should account for is that the buried vertical well did not reach a steady state during operation and so the change in pore pressure in the surrounding waste might be slightly higher than the results shown in this chapter. 3.4 Conclusion This paper presents the impact of leachate recirculation into buried vertical wells on the pore pressure in the surrounding waste in a full scale MSW landfill. After the multi level piezometers were installed, only 58 piezometers worked properly out of the 90 piezometers. Before leachate injection, the pore pressure measured by the VW piezometers increased significantly with the depth of the landfill indicating a decrease in permeability of the waste with an increase in the depth of the landfill. Since hig h landfill gas pressures were observed in the landfill, the gas pressure has to be accounted for in the slope stability analysis. The 58 piezometers responded to leachate recirculation to the vertical wells with increased pore water pressure measurements An initial time lag of 24 to 48 hours associated with reading the correct change in pore pressure due to the time taken to saturate the grout was observed, but once the grout became saturated, the piezometers responded within one hour of leachate recircul ation The shallow piezometers located close to the leachate injection well responded quickly to leachate addition, as compared to piezometers that were deeper and located far from the well. The pressures in the waste did not drop immediately after leachat e recirculation was stopped, but slowly decreased with time.

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68 The piezometers showed a steady increase in pore pressure in the surrounding waste over time and would continue to increase until the leachate addition in the well reached steady state. The the rmocouples showed a decrease in temperature when the moisture front hit the piezometers. The temperature decreased for the next couple of days due to colder temperature of the moisture added, after which it reached a thermal equilibrium between the moisture and the surrounding waste. This t emperature data indicated that most of the wetted piezometers were located up to a radial distance of 2.2m from the injection well over time, however one fourth of the piezometers were not wetted from 2.2 to 7.8 m radial distance from the vertical well. Even though large pressures were present in the bottom of a buried vertical well during leachate addition, pressures were significantly reduced in the surrounding waste. Even though the hydrostatic head increased with the depth of the vertical well during leachate injection, the pore water pressure in the surrounding waste did not increase proportionally, indicating that the permeability of waste was lower in the deeper sections of the landfill. Also, there was a significa nt reduction in the pore water pressure just three meters below the bottom of the buried vertical well which indicated the anisotropic nature of the waste. Thus, the side slope stability of the landfill due to leachate addition in the buried vertical well may not be a concern if a suitable distance is maintained from the side slope of the landfill.

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69 Figure 31. Plan view of NRRL indicating the buried vertical well clusters

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70 Q N R P O M L J A C I F B K G D H E W -1 W -2 7.6 m 1.5 m = W -1 and W -2: Buried vertical wells = A to R: Multi-level piezometer wells 0 m 1.5 m 3 m 4.6 m 6.1 m 7.6 m Radial distance from W -2 Figure 3 2. Plan view of the buried vertical wells and the multi level pi ezometer wells Figure 3 3. Cross section view of the buried vertical wells and the multi level piezometer wells 7.62 m 1.52 m 3 m

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71 Pore pressure (m of W.C.) 0 1 2 3 4 5 6 7 8 Depth of the landfill (m) 4 6 8 10 12 14 16 18 20 Figure 3 4. Pore pressure s measured by the VW Piezometers at various depths inside the landfill pr ior to leachate recirculation Days (1311 = 12-1-09) 1313 1314 1315 1316 Pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 40 45 50 55 60 65 70 Leachate injection pressure (m of w.c.) 10 12 14 16 18 20 22 Pore pressure Temperature Injection pressure (a) Piezometers at a depth of 5.8 m from surface of the landfill

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72 Days (1311 = 12-1-09) 1313 1314 1315 1316 Pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 50 55 60 65 70 75 Leachate injection pressure (m of w.c.) 10 12 14 16 18 20 22 Pore pressure Temperature Injection pressure Days (1311 = 12-1-09) 1313 1314 1315 1316 Pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 50 55 60 65 70 75 80 Leachate injection pressure (m of w.c.) 10 12 14 16 18 20 22 Pore pressure Temperature Injection pressure Days (1311 = 12-1-09) 1313 1314 1315 1316 Pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 60 65 70 75 80 85 90 Leachate injection pressure (m of w.c.) 10 12 14 16 18 20 22 Pore pressure Temperature Injection pressure Figure 3 5. Piezometer responses to leachate recirculation at various depths and at a fixed radial distance of 1.5m from the well during the first few days of operation at an average flow rate of 13.67104 m3/sec (d) Piezometers at a depth of 18 m from surface of the landfill (c) Piezometers at a depth of 11.9 m from surface of the landfill (b) Piezometers at a depth of 8.8 m from surface of the landfill

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73 Days 1313 1314 1315 1316 1317 1318 1319 1320 Pore pressure (m of w.c.) 0 1 2 3 4 5 Leachate injection pressure (m of w.c.) -40 -20 0 20 2.2 m 3.0 m 4.6 m 6.1 m Injection pressure Days 1313 1314 1315 1316 1317 1318 1319 1320 Pore pressure (m of w.c.) 0 1 2 3 4 5 Leachate injection pressure (m of w.c.) -40 -20 0 20 2.2 m 3.0 m 4.6 m Injection pressure Figure 3 6. Piezometer responses to leachate recirculation in radial direction from the vertical well during the first few days of operation at an average flow rate of 13.67104 m3/sec (a) Piezometers at a depth of 5.8 m from surface of the landfill (b) Piezometers at a depth of 14.9 m from surface of the landfill

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74 Days 1320 1340 1360 1380 1400 1420 1440 1460 Pore water pressure (m of w.c.) 0 2 4 6 8 10 Leachate injection pressure (m of w.c.) -40 -20 0 20 2.2 m (radial) 6.3 m (radial) Injection pressure Days 1320 1340 1360 1380 1400 1420 1440 1460 Pore water pressure (m of w.c.) 0 2 4 6 8 10 Leachate injection pressure (m of w.c.) -40 -20 0 20 2.2 m (radial) 6.3 m (radial) Injection pressure Days 1320 1340 1360 1380 1400 1420 1440 1460 Pore water pressure (m of w.c.) 0 2 4 6 8 10 Leachate injection pressure (m of w.c.) -40 -20 0 20 2.2 m (radial) 6.3 m (radial) Injection pressure (a) Piezometers at a depth of 5. 8 m from surface of the landfill (b) Piezometers at a depth of 8.8 m from surface of the landfill (c) Piezometers at a depth of 11.9 m from surface of the landfill

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75 Days 1320 1340 1360 1380 1400 1420 1440 1460 Pore water pressure (m of w.c.) 0 2 4 6 8 10 Leachate injection pressure (m of w.c.) -40 -20 0 20 2.2 m (radial) 6.3 m (radial) Injection pressure Days 1320 1340 1360 1380 1400 1420 1440 1460 Pore water pressure (m of w.c.) 0 2 4 6 8 10 Leachate injection pressure (m of w.c.) -40 -20 0 20 2.2 m (radial) 6.3 m (radial) Injection pressure Figure 3 7. Temporal impact of leachate inj ection on the pore pressure s of surrounding waste in radial direction and at a depth of (a) 5.8 m, (b) 8.8 m, (c) 11.9 m, (d) 14.9 m and (e) 18 m from the surface of the landfill (d) Piezometers at a depth of 14.9 m from surface of the landfill (e) Piezometers at a depth of 18 m from surface of the landfill

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76 Figure 3 8. Spatial impact on the pore pressure s of surrounding waste in radial direction and at a depth of (a) 5.8 m, (b) 8.8 m, (c) 14.9 m and (d) 18 m from the surface of the landfill during leachate recirculation at a pressure of 20 m of w.c.at the bottom of the buried vertical well and a flow rate was 6 x 104 m3/s Radial distance from the point of leachate re-circulation (m) 1 2 3 4 5 6 7 8 Pore water pressure ( m of w.c.) 0 5 10 15 20 Radial distance from the point of leachate re-circulation (m) 0 2 4 6 8 Pore water pressure ( m of w.c.) 0 5 10 15 20 (a) Depth = 5.8 m (b) Depth = 11.9 m (c) Depth = 14.9 m (d) Depth = 18 m Radial distance from the point of leachate re-circulation (m) 0 2 4 6 8 Pore water pressure ( m of w.c.) 0 5 10 15 20 Radial distance from the point of leachate re-circulation (m) 0 2 4 6 8 Pore water pressure ( m of w.c.) 0 5 10 15 20

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78 Figure 3 9. Spatial impact on the pore pressure s of surrounding waste in vertical direction and at a radial distance of (a) 2.15 m, (b) 3 m, (c) 6.3 m and (d) 7.8 m from the buried vertical well during leachate recirculation at a press ure of 20 m of w.c.at the bottom of the buried vertical well and a flow rate was 6 x 104 m3/s Pore water pressure ( m of w.c.) 0 2 4 6 8 10 12 Depth of the landfill (m) 4 6 8 10 12 14 16 18 20 Pore water pressure ( m of w.c.) 0 2 4 6 8 10 12 Depth of the landfill (m) 4 6 8 10 12 14 16 18 20 (a) Radial distance = 2.15 m (b) Radial distance = 3 m (c) Radial distance = 6.3 m (d) Radial distance = 7.8 m Pore water pressure ( m of w.c.) 0 2 4 6 8 10 12 Depth of the landfill (m) 4 6 8 10 12 14 16 18 20 Pore water pressure ( m of w.c.) 0 2 4 6 8 10 12 Depth of the landfill (m) 4 6 8 10 12 14 16 18 20

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79 CHAPTER 4 LANDFILL SETTLEMENT RESULTING FROM MOISTURE ADDITION USING VERTICAL WELLS 4.1 Introduction Accurate settlement prediction at municipal solid waste lan dfills can be very useful in designing and constructi ng of landfills as well as in the determination of landfill life span. The settlement mechanisms in MSW landfills are complex as compared with typical soil consolidation due to heterogeneous, anisotropi c material property and decompositional characteristics of the compacted waste in a landfill. Settlement has been described as occurring in three stages namely immediate, primary and secondary settlement ( El Fadel et al. 1999; Sowers 1973; Wall and Zeiss 1 995; Ling et al. 1998). Immediate settlement results from over burden pressure when an external load applied to the waste, while p rimary settlement occurs when pore water and gas dissipates from the void spaces of the matrix Both of these stages occur wi thin the first few months after the placement of waste. The last stage, secondary settlement, results from creep of the refuse skeleton and decomposition of organic waste, and account s for a majority of the settlement at landfills The primary cause of s econdary settlement at landfills is volume reduction due to the decomposition of the organic waste component The decomposition of organic waste occurs to some extent in all landfills, but is accelerated by operating the landfill as a bioreactor (Reinhart and Townsend 1998; Warith et al. 2002; Hossain et al. 2003). A bioreactor landfill operates to rapidly transform and degrade organic waste (US EPA 2007). The increase in waste degradation and stabilization is accomplished primarily through the addition of leachate or other liquids The addition of moisture has been demonstrated repeatedly to have a stimulating effect on degradation of organic waste (Rees et al. 1980; Pohland et al. 1988; Barlaz et al. 1990). The decomposition of organic waste into the gas phase takes place resulting in the formation of void

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80 spaces. These void spaces between the larger particles get filled with fine materials resulting in settlement of the waste. In addition to this in a bioreactor landfill, moisture addition increase s the sp ecific weight of the waste in a bioreactor landfill. Increased specific weight results in greater mechanical settlement of the landfill. Since moisture addition is a key element in the successful operation of a bioreactor landfill, it is valuable to know t he effects of moisture addition on landfill settlement. S everal mathematical models (Wall and Zeiss 1995 ; Bowders et al 2000; Park and Lee 2002; Durmusoglu et al 2005; Hettiarachchi et al 2006; Swati and Joseph 2008) have been reported for the predicti on of settlement in a MSW landfill, but the validity and accuracy of these models are questionable due to the complex nature of compacted landfill waste. Hence, settlement prediction based on practical experience, monitoring and observational procedures can be very helpful Based on the literature review conducted by Townsend et al. (2009), the typical settlement rate for a conventional dry landfill is approximately 1.24% of the initial height per year and the typical settlement rate for a bioreactor lan dfill is approximately 3.7% of the initial height per year. Yazdani et al (1999) designed and constructed five experimental facilities at Yolo County Landfill, CA and reported an average settlement rate of bioreactor test cells as 2.4% per y ea r compared to just 0.5% per year for conventional landfills. El Fadel et al. (1999) designed and constructed five test cells considered as representative of actual scale anaerobic bioreactor landfills and one test cell operat ed as a conventional landfill They report ed a settlement rate of 2.933.83 % per y ea r for bioreactor test cells as compared to just 1.93% per year for conventional landfills. Benson et al. (2007) reported a comparison of the landfill gas flow rate and settlement of a bioreactor cell with that of a conventional dry landfill cell and found that the bioreactor cell yielded 2.3 times more methane and settled 10% more than the

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81 conventional landfill cell during the study period. Little information is available on the different roles that moisture plays on landfill settlement at the operation level. This paper presents the findings of a settlement investigation conducted l at the New River Regional Landfill (NRRL) in Union County. The objective of the research was to evaluate the effect on landfill se ttlement resulting from moisture addition using vertical wells The NRRL bioreactor was divided into two areas, namely aerobic and anaerobic, as shown in Figure I 1 of appendix I. The majority of the l eachate recirculation was carried out in the anaerobic area of the bioreactor while the aerobic area of the bioreactor was kept relatively dry for air addition. This research focused on how the overall settlement varied with the amount of leachate recirculated and the moisture content of the waste in the biore actor landfill. Due to the way in which waste in is deposited and compacted in a landfill, it is commonly regarded as anisotr opic (Townsend et al. 1995; McCreanor et al. 1998; Landva et al. 1998). An objective of this research was to characterize the sett lement in various layers of the landfill and the impact of moisture content on the settlement in various layers. 4.2 Materials and Methods 4.2.1 Site Configuration The NRRL receives approximately 1,000 metric tons per day of waste consisting of mixed resi dential and commercial waste. At the time of this research, t he landfill consisted of five contiguous lined landfill cells totaling approximately 30 hectares, as shown in Figure 4 1. The compacted density of the landfilled waste has been estimated to be 710 kg/m3. A clayeysandy soil mined on site was used as daily cover. Approximately 4 hectares (Cell 1 and part of Cell 2) were retrofitted to operate as a bioreactor landfill. Cell 1 is approximately 2 hectares in area and is equipped with a composite bot tom liner and Cell 2 is approximately 3.6 hectares and is equipped with a double liner system. Thirty one gas collection trenches were installed to

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82 collect landfill gas. Each trench is provided with a gas well consisting of a HDPE pipe booted through the e xposed geomembrane cap (EGC). A gas well was also installed at the lift station to collect landfill gas captured by the leachate collection system. The bioreactor was covered with a 1mm textured polyethylene geomembrane underlain by approximately 0.6 m of cover soil. A detailed description of the site and the bioreactor can be found elsewhere (Jain 2005). 4.2.2 Operation of the Bioreactor A series of vertical wells w ere installed to add moisture and add air to the landfilled waste. The system consist ed of 45 clusters of vertical wells located at distance of at least 15 m away from each other and was installed in the spring of 2001. Figure I 1 in appendix I presents a plan view showing locations of individual vertical well clusters. Each cluster contained three wells (with the exception of one cluster that had two wells) with approximate depths of 6, 12 and 18 m as shown in Figure 42. The vertical wells in each cluster were approximately 0.6 m apart. Only the bottom portions of these vertical wells were sc reened to add leachate/air into different layers of the waste. The vertical well clusters on the right side of section A A as shown in Figure I 1 of appendix I were on the aerobic part of the bioreactor; little or no leachate was added in these vertical w ells to keep them relatively dry for the purpose of testing air addition. Minimal air was ever added because of difficulties in controlling the temperature of the waste during air addition. The remaining vertical well clusters on the left side of section A A were on the anaerobic part of the bioreactor. Leachate was recirculated in various vertical well clusters intermittently from 2003 until 2007. A total of 400 to 1000m3 of leachate was injected in each vertical well cluster The leachate generated in ot her cells at the site was also added to the bioreactor. Groundwater was used as a supplemental source of moisture if enough leachate was not available. Magnetic meters were installed to tra ck the total volume of leachate and makeup water recirculated as well as the volume of leachate produced from Cell 1 and 2. The

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83 instantaneous and cumulative leachate addition rates for individual vertical wells were monitored once per day using ABB single jet impeller meters. Jain et al. (2005) evaluated the performance of vertical well system for leachate recirculation to provide some of the inputs for design of similar systems for future bioreactors. A series of monitoring wells containing MTG sensors were also installed throughout the bioreactor area Jonnalagadda ( 2004), evaluated the effectiveness of the MTG sensors for in situ measurement of landfilled waste moisture content at bioreactor landfills. 4.2.3 Settlement and Moisture Content Measurements The settlement of the waste was monitored using a Z model dual frequency real time kinematic (RTK) global positioning system (GPS) (Z surveyor by Ashtech /Magellan ) and had an accuracy of 0.01m Settlement measurements were taken immediately after installing the vertical well clusters and the monitoring wells in 2002, and were repeated once every 45 day throughout the period of leachate addition until June 2007. Permanent concrete benchmarks, (placed next to the vertical well clusters) and the monitoring wells were surveyed to measure the settlement on the landfill sur face and the monitoring wells as shown in Figure 42. The vertical wells in a cluster were designed to add leachate at various layers in the waste of the landfill. Hence s urveying was done on top of shallow middle and deep vertical wells to measure settle ment at various depths of the landfill as shown in Figure 42. MTG and TDR sensors were used to measure the in situ moisture content periodically. Because of potential wetting of the sensors via channeling and preferential flow, Dinesh et al. (2009) sugge sted that caution should be taken to extend the moisture content values that are representative of waste surrounding the sensors to estimate the overall moisture content on a landfillwide scale. In order to determine more realistic values of moisture cont ent, solid waste samples were augured after operating the landfill as a bioreactor to determine the moisture content A total of 29 boreholes were drilled at various

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84 locations throughout the bioreactor area in summer 2007. Twenty Six boreholes wells were 12 m deep and the remaining three boreholes were 15 m deep. Samples were collected every 1.5 meter layers. The moisture content of these samples was measured by gravimetric analysis. The gravimetric moisture content was estimated by oven drying (at 102C) a 510 kg of sample over the duration of 12 24 hours until the sample weight stabilized. Moisture content values based on the mass balance approach were estimated. Details of this procedure can be found elsewhere in Kumar et al. ( 2009 ) 4.2.4 Data Managemen t The performance evaluation of vertical well system for leachate recirculation at NRRL by Jain (2005), indicated that the extent of lateral moisture movement from the point of liquid injection in waste was estimated to range from 8 10m. So, in order to characterize the settlement as a function of the moisture addition, the boundary of the bioreactor area was defined by selecting an area of 100 m by 100m such that the outer vertical well clusters in the bioreactor area are less than the 10 m from the define d boundary as shown in Figure I 1 of Appendix I. A total of 29 boreholes were drilled within the defined bioreactor area to determine the moisture content at various locations. Surfer 8 software (Golden Software, Inc.) was used to estimate the surface of t he bioreactor landfill before and after leachate recirculation using the s urvey data from 2002 and 2007 respectively. The software was used to create a 100 by100 node grid (with 10000 node points) with the known height and the coordinates of the vertical a nd monitoring wells for 2002 and 2007. V alue to these 100,000 node points were assigned based on their locations with respect to the surrounding vertical or monitoring wells (for which the height value were known) using the Kriging Method (Linear Variogram Model). The change in volume of the bioreactor from 2002 to 2007 by calculated using the extended trapezoidal rule The cross sections of the landfill were determined using the slicing method of the surfer software.

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85 T o determine the change in settlement due to moisture addition, the landfill was divided into 16 equal sections of 25 by 25 m as shown in Figure I 3 of Appendix I S patial average percentage settlement were calculated for all the 16 sections using the Kriging Method (Linear Variogram Model) by surfer software. Since, it is not possible to determine the exact quantity of leachate recirculated in each section, the follo wing assumptions were made. A total of 33 vertical well clusters were at least 4 meters away from the edge of each section. The amount of leachate injected in these vertical well clusters was dissipated uniformly in its corresponding section only. The r emaining 12 vertical well clusters were at most 2 meters away from the edge of its section. Hence the amount of leachate injected in this cluster was shared equally by the adjacent section as well. To assess the influence of moisture content on the settle ment in various layers of the landfill, each of the 16 sections was divided into 4 layers depending upon the average depths of shallow, middle and deep vertical wells as measured in 2007. These four layers have been classified as the top, upper middle, low er middle and bottom layers within the landfill as shown in Figure J 1 of Appendix J. Spatial average settlement percentage and moisture content were calculated for each layer in all the 16 sections using the Kriging Method (Linear Variogram Model) by surf er software. 4.3 Results and Discussion 4.3.1Settlement and the Average Space Gained Over the Bioreactor Operation Period Figure 4 3 presents the average settlement occurring at the surface and at various depths of the landfill from June 2002 until Octobe r 2007. A total of 23,772m3 (6.3 million gallons) of leachate and groundwater was added intermittently using the vertical well system for approximately 3 years from June 2003 until May 2006. Prior to June 2003, when leachate

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86 recirculation was not started, a majority of the settlement occurred in the bottom layer of the landfill. This might be due to higher moisture content in the bottom layer of the landfill causing accelerated decomposition of the waste. However, after starting leachate addition, settlement occurred in all the layers of the landfill. This might be due to the accelerated decomposition of waste resulting from moisture addition entering in the various layers of the landfill as well as the additional over burden pressure of the leachate. The surface of the landfill settled an average of 2.48 m (8.1ft) or 11.3% of the initial height in a period of 5.3 years. The average rate of settlement was 2.11 % of the initial height per year. Edil et al. (1990) reported a settlement rate of 1.13% per year f or a conventional landfill in Wisconsin. Yuen et al. (1999) reported a settlement rate of 1.4% per year for a conventional l andfill and a settlement rate of 2.3% for a bioreactor landfill in Australia. El Fadel et al. (1999) reported an average settlement of approximately 3% per year. Based on the literature review, the settlement that occurred at the NRRL bioreactor was lower than other reported bioreactor landfills. This could be due to several factors that determine the rate of settlement in a bioreactor landfill. These factors include the amount of leachate injected, the period of leachate recirculation, the uniform distribution of injected leachate throughout the bioreactor area and different biodegradable fraction in the waste. Figure 4 4 presents th e air space gained from the surface of the landfill and at various depths along with the cumulative volume of leachate recirculated over time. The potential air space gained during the bioreactor operation from 2002 until 2007 was 20,482m3. The air space g ained was lower during the initial period of leachate recirculation, compared to the end of the leachate recirculation period. During the initial period of leachate recirculation, the settlement in the waste would be mainly due to increased specific weight of the waste. However, at the end of

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87 leachate recirculation period, the settlement in the waste would be due to both accelerated waste decomposition and increased specific weight of the waste. 4.3.2 Total Settlement at Various Cross Sections of the Bioreactor Figure I 2 in appendix I shows the elevation contours of the landfill in 2002 and 2007. To illustrate the change in the surface of the landfill due to settlement, the bioreactor area was divided into two cross sections namely B B and C C as shown i n Figure I 1 of appendix I. Figure 45 (a) and (b) shows the cross section of the landfill indicating the change in surface of the landfill from the bottom in a period of 5.35 years. The graphs show that at the end of the bioreactor operation there was une ven settlement on the surface of the landfill. The aver age rate of settlement was 2.11% of the initial height per year compared to typical settlement rate of 3.7% of the initial height per year for a bioreactor landfill based on a literature review (Townse nd et al. 2009). The average moisture content of the bioreactor was 23% prior to leachate recirculation based the waste samples augured from the bioreactor area. Since, the total amount leachate recirculated was 6.28 million gallons; the moisture content in the bioreactor should have increased to 26.75% without considering the amount of leachate generated. However, the average moisture content based the waste samples augured from the bioreactor area was close to 40%. This indicates that the moisture was not uniformly distributed throughout the bioreactor area. This could be one of the reasons for a lower settlement rate compared to the literature review. As mentioned earlier in this chapter, the settlement in a bioreactor landfill is primarily due to accelerated decomposition of the waste as well as an increase in overburden pressure due to the added leachate. So, the settlement that occurred at NRRL was calculated and is shown in Appendix J. Based on the equations developed by McKnight (2005) the settlement due to the overburden pressure of the added leachate is 2.6%. Based on the waste samples augured from

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88 2001 and 2007, the settlement due to the decomposition of the waste is 24.6%. Hence, the total settlement in the landfill based on both the above criteri a should be 27.2%. This suggests that the overall settlement at NRRL is lower than the expected settlement. Since majority of the calculated settlement is due to decomposition waste, this suggests that the settlement due to waste decomposition has not full y taken place. This could be due to nonuniform moisture distribution in the waste. To further understand the difference between actual and calculated settlement, the settlement in various layers of the landfill was calculated. 4.3.3 Settlement in Various Layers of the Landfill Figure 46 shows the average settlement percentage in various layers of the landfill. The top and the bottom layers had settled by an average of 14.5 and 12.7%, respectively, as compared to the upper and the lower middle layers that had settled 9.9 and 8.8%, respectively. The higher settlement in the top and bottom layers compared to the middle layers might be due to an increase in the dissipation of pore pressure of leachate and gas generated by the waste either through the leachate collection system or through the surface of the landfill The bottom layer of the landfill had the highest over burden pressure compared to the remaining layers of the landfill. Also, the bottom layer had a higher moisture content compared to the other lay ers causing a potential increase in waste degradation resulting in higher gas production. This increase in over burden pressure and accelerated waste decomposition might be responsible for the dissipation of pore pressure of leachate and gas generated by t he waste through the leachate collection system resulting in a higher settlement. The top layer ha d a higher percentage settlement due to the dissipation of pore pressure of leachate and gas generated by the waste directly to the surface of the landfill. A lso surface gas collection trenches had been installed to remove gas generated from the surface of the landfill by applying vacuum.

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89 A majority of leachate was added in the middle layers of the landfill. Also, the moisture content data from waste samples augured in 2007 also indicates higher moisture content in the middle layers of the landfill as shown in Figure I 5 of appendix I. The waste might be under consolidated immediately after the new load (water) was applied but before the excess pore water pressure has had time to dissipate. The large volumes of moisture trapped within the particles of waste might have resulted in lower settlement in the middle layers in the landfill. Also, the amount of leachate generated did not change significantly due to leachate recirculation indicating that moisture is still trapped in the waste. This could be the reasons for higher predicted settlement compared to the actual settlement observed at NRRL. 4.3.4 Lateral Settlement around the Vertical Well Clusters Vertical well clusters with leachate addition settled more than the surrounding monitoring wells resulting in uneven surface of the landfill at the end of the bioreactor operati on (Figure 45). To estimate the lateral settlement around the vertical well clusters due to leachate addition, the impact on six vertical well clusters with and without leachate addition were chosen. T he average settlements percentage of these vertical w ell clusters was compared with their surrounding monitoring wells. A total of 2,000 m3 of leachate was added in the three vertical well clusters where no leachate was added in the other clusters. Figure 47 shows the impact of leachate recirculation on th e lateral settlement percentage from the vertical wells. Single factor analysis of variance (ANOVA) indicated that the settlement percentage decrease significantly with radial distance from the vertical wells with leachate addition [F (2,7) = 6.99, P = 0.02] as compared to vertical wells with no leachate addition [F (2,11) = 1.14, P = 0.35] The higher waste settlement around the vertical wells with leachate addition may be attributed to compression of waste due to an increase in overburden pressure This i ncrease in overburden pressure is caused by an increase in the specific weight of the waste as a result of leachate

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90 addition. The average settlement of the vertical wells with leachate injection was around 4% higher than the vertical wells with no leachate injection. As previously mentioned, the settlement due to the overburden pressure of the added leachate is 2.6% for the bioreactor. So, the higher waste settlement can be attributed to accelerated waste decomposition due to leachate addition resulting in the raveling of the waste mass 4.3.5 Impact of Leachate Addition on Settlement in Various Sections of the Landfill Since there was differential settlement among the vertical wells and the monitoring wells, the landfill was divided into 16 equal sections ( 10m x 10m area) to characterize the impact of leachate addition on settlement in various sections of the landfill. Figure I 3 in appendix I shows the schematic diagram of various sections of the bioreactor area along with the corresponding settlement percentage and the amount of leachate added From the schematic diagram it was observed that i n general, the relatively dry areas of the landfill ha d settle d less as compared to the wet areas of the landfill. These sections were further grouped together based upon the cumulative volume of leachate added in the various sections of the landfill to determine the average settlement percentage as shown in Figure 48. Single factor analysis of variance (ANOVA) indicated that the average settlement percentage differs s ignificantly between 0 800 m3 and 1,6002,400 m3 of leachate addition [F (1,8) = 8.3, P = 0.02], however the average settlement percentage did not differ significantly between 0 800 m3 and 8001600 m3 [F (1,8) = 1.98, P = 0.20]or 8001,600 m3 and 1,6002,400 m3 [F (1,10) = 0.30, P = 0.59] of leachate addition. Also the standard deviation in settlement between 0 800 m3 and 8001600 m3 of leachate addition is higher as compared to 1,6002,400 m3. This could be due to the preferential flow of the leachate from one section to another due to the heterogeneous and anisotropic nature of the waste in the landfill.

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91 Also few sections of the landfill were close to the side slope of the landfill. The over burden pressure is less on the side slope of the landfill as com pared to the inner sections of the landfill that are piggybacked by all sides. This can result in the dissipation of pore pressure of leachate and gas generated by the waste through the side slope of the landfill causing further settlement in the landfill. For example, in Figure I 3 of appendix I, it is observed that sections close to the side slope of the landfill such as sections 5 and 9 had settled an average of 1% more than the inner sections 6 and 10, even though more amount of leachate was added in the inner sections. The 16 sections were further classified into outer and inner sections within the bioreactor area to eliminate the sections whose settlement could be impacted either due to the side slope of the landfill or by piggybacking to another cell Figure 49 indicates that the inner sections of the bioreactor show a substantial increase in the settlement percentage with increase in leachate addition. 4.3.6 Impact of Leachate Addition on the S ettlement in Various Layers of the Landfill Figure I 4 in appendix I shows the impact of moisture content on the s ettlement in various layers of the landfill. Single factor analysis of variance (ANOVA) indicated that there was no significant increase in settlement with increase in moisture content in various layers of a landfill. The moisture content in a layer per section (25m x 25m) was determined by averaging the moisture content data obtained from only 1 to 3 locations. Also, the compacted waste mass in a landfill is highly heterogeneous and anisotropic na ture. Hence, the average moisture content obtained from the field samples might not be a true representative of the actual moisture content in the 25 x 25 m2 section.

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92 4.4 Conclusion Over 23,000m3 (6.3 million gallons) of leachate and groundwater was adde d intermittently using the vertical well system in the bioreactor from June 2003 until April 2007 at NRRL The surface of the landfill settled an average of 2.48m (8.1ft) or 11.3% of the initial height in period of 5.3 years. The settlement occurred mainly due to the decomposition waste, but partly due to the overburden pressure of the waste. The potential air space gained due to sett lement in the landfill was 20,482 m3. The average settlement rate of the landfill was 2.11 % of the initial height per year during the 5.35 years of bioreactor operation. Settlement percentage was higher in the top and the bottom layers compared to the middle layers of the landfill likely due to an increase in the dissipation of pore pressure of leachate and gas generated by the waste either through the leachate collection system or through the surface of the landfill Majority of leachate was added in the middle layers of the landfill. The waste might be under consolidated immediately after the new load (water) wa s applied but before the excess pore water pressure has had time to dissipate. This might have resulted in lower settlement in the middle layers in the landfill. The higher waste s ettlement was observed around the vertical wells with leachate addition compared to the vertical wells with no leachate addition. The average settlement percentage in the various sections of the landfill inc reased significantly between 0 800 m3 and 1,6002,400 m3 of leachate addition Results indicated that there wa s no significant increase in settlement with increase in moisture content within the various layers of a landfill. One of the possibilities is that the average moisture content obtained from the field samples might not be a true representative of the actual moisture content Hence, future work should focus on how the settlement in the various layers of the landfill is impacted due to variation in moisture content.

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93 Bioreactor Area Figure 41. Plan view of new river regional landfill indicating the bioreactor area (Adapted from as buil t drawings provided by Jones Edmunds and Associates )

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94 Figure 4 2. Schematic v iew of a vertical well cluster and monitoring wells Time (Year) 02 03 04 05 06 07 08 Settlement (m) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Cumulative volume of leachate recirculated (x 1000 m 3 ) 0 5 10 15 20 25 Landfill surface 18 m depth 12 m depth 6 m depth Leachate recirculated Figure 4 3. Set tlement at the surface and at various depths in the landfill over time with leachate recirculation 18 m 12 m 6 m Landfill Surface Bottom Liner 22 m Concrete mogul for surveying Vertical well cluster Monitoring wells Surveying locations for settlement measurement

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95 Time (Year) 02 03 04 05 06 07 08 Air space gained (m 3 ) 0 5000 10000 15000 20000 Cumulative volume of leachate recirculated (x 1000 m 3 ) 0 5 10 15 20 25 Top Depth 6 m Depth 12 m Depth 18 m leachate recirculated Figure 4 4. Air space gained from the surface of the landfill and at various depths along with the cumulative volume of leachate recirculated over time Cross-sectional distance AA' (m) 0 20 40 60 80 100 Height of the landfill (m) 10 12 14 16 18 20 22 24 26 28 Landfill surface 6-24-02 Landfill surface 10-9-07 Landfill bottom (b) B B

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96 Cross-sectional distance BB' (m) 0 20 40 60 80 100 Height of the landfill (m) 10 12 14 16 18 20 22 24 26 28 Landfill surface 6-24-02 Landfill surface 10-9-07 Landfill bottom Figure 4 5. Cross section of the landfill indicating the change in landfill surface due to settlement over period of 5.35 years Various layers in the landfill Top Upper middle Lower middle Bottom Settlement (%) 0 2 4 6 8 10 12 14 16 Figure 4 6. Settlement percentage in various layers of the landfill (a) C C

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97 Figure 47. Average lat eral settlement from the vertical wells with and without leachate addition Cumulative volume of leachate recirculated (m 3 ) 0-800 800-1600 1600-2400 Average settlement (%) 8 9 10 11 12 13 14 Figure 48. Average s ettlement due to leachate addition in various sections of the landfill Lateral distance from the vertical wells Vertical Wells 7-11 (m) 11-15 (m) Average settlement (%) 6 8 10 12 14 16 Lateral distance from the vertical wells Vertical Wells 7-11 (m) 11-15 (m) Average settlement (%) 6 8 10 12 14 16 Leachate injected No Leachate injected

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98 Amount of leachate added in the inner section of the bioreactor (m 3 ) 400 800 1200 1600 2000 2400 2800 Settlement % 11.0 11.5 12.0 12.5 13.0 Figure 49. Settlement due to leachate addition in the inner sections of the landfill

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99 CHAPTER 5 SUMMARY AND CONCLUSI ONS 5.1 Summary An emerging waste management trend in the United States is to operate a landfill as a bioreactor. E ffective moisture addition is a key to bioreactor operation and this is most commonly accomplished using l eachate recirculation Vertical wells are relatively common in retrofit landfills Vertical wells were installed at the New River Regional Landfill (NRRL); Jain et al. (2005) evalua ted the performance of these wells for landfill leachate recirculation and several of the lessons learn ed prompted the current research. This dissertation is organized into three primary research objectives. The first objective was to inject leachate in b uried vertical well clusters at a pressure higher than the well screen length without causing surface seeps on the landfill and to characterize performance. Six buried vertical well clusters were installed at NRRL ; replicate clusters of 6, 9, and 12 m dept hs were constructed using an open flight auger. Each cluster contained 9 vertical wells connected to a single leachate recirculation lateral. A 4 m lift of waste was placed on top to bury the vertical well clusters. A cumulative volume of 8,431 m3 (2.2 mil lion gallons) of leachate was recirculated intermittently in the well clusters over a period of 153 days without causing any surface seeps Of the six well clusters one well cluster was clearly damaged and thus not used in the research. The average flow r ate varied from 9.3104 to 14.2104m3/sec (14.7 to 22.5 gpm) with an increase in the well depth from 6 to 9m respectively Leachate was in jected under a pressure of 6.13 to 6.39 m of w.c. in the buried vertical well clusters. Since there was significant reduction in pressures between the first and the last vertical well in the cluster during leachate recirculation, not all the available screen length was used during the initial period of leachate re circulation.

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100 However, as the time progressed, the press ure at the bottom of the wells was almost the same except when leachate recirculation system was running. This suggests that the leachate was eventually getting distributed in all the vertical wells of a cluster. Comparison to field test results of Jain et al. ( 2005) indicated that the average leachate flow rate per unit screen length of the buried vertical well clusters was almost the same or higher compared to the conventional vertical wells. However the biggest advantage of using this method is that cons tant monitoring of the leachate recirculation system was not required and the ability to inject leachate in the buried vertical wells at a pressure higher than the screen length of the vertical well without causing surface seeps on the landfill Also, the maintenance of the landfill was easier as fewer leachate injection lines penetrated from the side slope of the landfill. Due to occasional leaks on leachate injection lines on the side slope of the landfill and possible kinks inside the lateral leachate i njection lines, it is recommended to use a thicker HDPE pipe such as SDR 11 for future applications. The second objective of this research was to examine the temporal and spatial impact of leachate recirculation into buried vertical wells on the pore water pressure in the surrounding waste in a full scale MSW landfill. Two 12.2 m deep buried vertical wells were installed at a distance of 7.6 m apart each other. Surrounding these vertical wells were 18 multi level VW piezometer wells at a distance of 1.5 m f rom each other. Each multi level VW piezometer wells contained five VW piezometers at a distance of three meters from each other. After the multi level piezometers were installed, only 58 of the 90 piezometers were found to work properly. Before leachate injection, the pore pressures measured by the VW piezometers increased significantly with the depth of the landfill Results using the numerical model developed by Townsend et al. (2005) suggested that a lower permeability of waste was required

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101 to cause su ch high gas pressures in the landfill. The fact that the pore pressures increases with increase in the depth of the landfill could be due a decrease in permeability with the depth of the landfill as observed by Jain et al. (2005) in the air injection test. Since high landfill gas pressures were observed in the landfill, the gas pressure has to be accounted for in the slope stability analysis. The 58 piezometers responded to leachate recirculation to the vertical wells with increased pore water pressure meas urements An initial time lag of 24 to 48 hours associated with reading the correct change in pore pressure due to the time taken to saturate the grout was observed, but once the grout became saturated, the piezometers responded within one hour of leachat e recirculation The shallow piezometers located close to the leachate injection well responded quickly to leachate addition, as compared to piezometers that were deeper and located far from the well. The pressures in the waste did not drop immediately aft er leachate recirculation was stopped, but slowly decreased with time. The piezometers showed a steady increase in pore pressure in the surrounding waste over time and would continue to increase until the leachate addition in the well reached steady state. The thermocouples showed a decrease in temperature when the moisture front hit the piezometers. The temperature decreased for the next couple of days due to colder temperature of the moisture added, after which it reached a thermal equilibrium between the moisture and the surrounding waste. This t emperature data indicated that most of the wetted piezometers were located up to a radial distance of 2.2m from the injection well over time, however one fourth of the piezometers were not wetted from 2.2 to 7.8 m radial distance from the vertical well. Even though large pressures were present in the bottom of a buried vertical well during leachate addition, pressures were significantly reduced in the surrounding waste. Even though

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102 the hydrostatic head increased with the depth of the vertical well during leachate injection, the pore water pressure in the surrounding waste did not increase proportionally, indicating that the permeability of waste was lower in the deeper sections of the landfill. Also, there was a significant reduction in the pore water pressure just three meters below the bottom of the buried vertical well which indicated the anisotropic nature of the waste. Thus, the side slope stability of the landfill due to leachate addition in the buried ver tical well may not be a concern if a suitable distance is maintained from the side slope of the landfill. The third objective of this research was to evaluate the effect on landfill settlement resulting from moisture addition using vertical wells based on the settlement investigation conducted in a bioreactor area of NRRL Since the waste in a landfill is commonly regarded as anisotropic, one of the objectives of this research was to characterize the settlement in various layers of the landfill, and the imp act of moisture content on the settlement in various layers of the landfill. Over 23,000m3 (6.3 million gallons) of leachate and groundwater was added intermittently using the vertical well system in the bioreactor from June 2003 until April 2007 at NRRL The surface of the landfill settled an average of 2.48m (8.1ft) or 11.3% of the initial height in period of 5.3 years. The settlement occurred mainly due to the decomposition waste, but partly due to the overburden pressure of the waste. The potential air space gained due to sett lement in the landfill was 20,482 m3. The average settlement rate of the landfill was 2.11 % of the initial height per year during the 5.35 years of bioreactor operation. Settlement percentage was higher in the top and the bottom la yers compared to the middle layers of the landfill, likely due to an increase in the dissipation of pore pressure of leachate and gas generated by the waste either through the leachate collection system or through the surface of the landfill Majority of l eachate

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103 was added in the middle layers of the landfill. The waste might be under consolidated immediately after the new load (water) wa s applied but before the excess pore water pressure has had time to dissipate. This might have resulted in lower settlement in the middle layers in the landfill. The higher waste settlement was observed around the vertical wells with leachate addition compared to the vertical wells with no leachate addition. The average settlement percentage in the various sections of the landfill inc reased significantly between 0 800 m3 and 16002400 m3 of leachate addition 5.2 Conclusion Conclusions obtained through this research are summarized as fo llows: A cumulative volume of 8431 m3 (2.2 million gallons) of leachate was recirculated intermittently in the buried vertical well clusters at a pressure higher than the screen length of the vertical well. No seeps were found during the entire period of l eachate recirculation using the buried vertical wells. The average flow rate varied substantially with increase in the well depth of the vertical well cluster. Comparison of field test results indicated that the average leachate flow rate of the buried ver tical well clusters was almost the same compared to the conventional vertical wells. Before leachate injection, the pore pressure in the waste increased significantly with the depth of the landfill indicating a decrease in permeability of the waste with an increase in the depth of the landfill. The piezometers showed a steady increase in pore pressure in the surrounding waste over time during leachate recirculation and would continue to increase until the flow rate of leachate in the well reached a steady state. Even though large pressures were present in the bottom of a buried vertical well during leachate injection it significantly reduced in the surrounding waste. Hence the stability of the landfill due to leachate addition in the buried vertical wells may not be concern if a suitable distance from the side slope of the landfill is maintained.

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104 Even though the hydrostatic head increased with the depth of the vertical well during leachate injection, the pore water pressure in the waste did not increase proportionally suggesting that the permeability of waste was lower in the deeper sections of the landfill. There was a significant reduction in the pore water pressure in just few meters below the bottom of the buried vertical well which indicates the anisotr opic nature of the waste. The surface of the landfill settled an average of 2.48m (8.1ft) or 11.3% of the initial height in period of 5.3 years after bioreactor operations. Settlement percentage was higher in the top and the bottom layers compared to the middle layers of the landfill due to leachate addition. The higher waste settlement was observed around the vertical wells with leachate addition compared to the vertical wells with no leachate addition. The average settlement percentage increased signifi cantly between 0 800 m3 and 16002400 m3 of leachate addition. 5.3 Future work The results from this research were used to compare the average leachate flow rate of the buried vertical well clusters with the conventional vertical wells. More field studies should be undertaken to compare specific capacity of the buried vertical well clusters with the conventional vertical wells. Since t here was significant reduction in pressures between the first and the last vertical well in the cluster during leachate reci rculation not all the available screen length was getting used during the initial period of leachate re circulation Hence, it may be worth redesigning the manifold system so that leachate gets more evenly distributed in all the vertical wells in the clus ter during leachate re circulation. Temporal impact of leachate re circulation indicated a steady increase in pore water pressure in the surrounding waste Using the design charts for liquids addition in a vertical well system developed by Townsend et al (2006), the total volume of leachate that needs to be added to the well to reach a steady state is 26,350 m3. This suggests that the pore water pressure will

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105 further increase in the surrounding waste with leachate addition as only a limited quantity leachate was added in the vertical well compared to the volume to reach the steady state. Hence, further leachate recirculation needs to be carried out to see the impact on pore water pressure in the surrounding waste at steady state. Also it might be valuable to see the impact of pore water pressure in the surrounding waste due to simultaneous leachate recirculation into two vertical wells at a given distance from each other. Results indicated that there wa s no significant increase in settlement with increase in moisture content within the various layers of a landfill. One of the possibilities is that the average moisture content obtained from the field samples might not be a true representative of the actual moisture content Hence, future work should focus on how the settlement in the various layers of the landfill is impacted due to variation in moisture content.

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106 APPENDIX A CONSTRUCTION PHOTOS OF THE BURIED VERTIC AL WELL CLUSTERS The appendix shows some of the construction photos of the buried vertical well clusters at the New River Regional Landfill, Florida. Figure A 1. Drilling a vertical well in a trench using the solid stem open flight auger drilling rig on the surface of the landfill. Figure A 2. Pointed tail bit attached to the tip of the solid stem open flight auger Drilling rig 0.75 1 m deep 11.5 cm diameter s olid stem 1 m width

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107 Figure A 3. Insertion of slotted pipe through the temporary HDPE pipe Figure A 4. Customized pipe assembly being placed inside the drilled vertical well

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108 Figure A 5. Datalogger to measure and record pressure and temperature data from the piezometers and thermocouple wires

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109 = 0 453 2 2 1 33 = = = 4 APPENDIX B HEAD LOSS DUE TO FRI CTION The leachate injection pressure in the modified vertical wells was calculated by subtracting the head loss due to elevation and frictional loss in the pipe. The Mannings equation was used to calculate head loss due to friction in the pipe, which is an empirical equation that applies to uniform flow in open channels and is a function of the channel velocity, flow area and channel slope. ---------------------------------(1) Where: V= Cross sectional average velocity, (ft/s) n = Mannings Roughness Coefficient R = Hydraulic Radius, (ft) S = Channel Slope, (ft/ft) Velocity of the fluid is calculated b y the following equation. ---------------------------------(2) Where: Q = Flow Rate, (ft3/s) A = Flow Area, (ft2) The hydraulic radius is calculated by the following equation. ------------------------------(3) Where: A= Area of the pipe (ft2) P= Wetted perimeter (ft) D= Diameter of the pipe (ft)

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110 = = 2 2 The head loss in the pipe is given by the following equation. -------------------------------(4) Where: hl= Head loss in the pipe (ft) L = Length of the pipe (ft) The minor losses due to local disturbances of flow due to elbows and tees in the buried vertical wells were calculated using the following equation. ------------------------------(5) The following assumptions were made while making these calculations. Flow rate of the leachate = 30 gpm Mannings roughness coefficient for HDPE pipe = 0.009 Internal diameter of the HDPE pipe of nominal size 3 = 3.475 inch = 0 3 = 0 2 The total head loss for the buried well cluster F is calculated in the following example. Lengt h of the pipe = 850 ft The velocity of the fluid is, = 30 0 002228 2 2 3 14 3 475 12 2 = 1 015 /

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111 The hydraulic radius is, = 3 475 12 4 = 0 0724 The channel slope is, = 0 453 1 015 2 0 009 2 0 724 1 33 = 0 001243 The head loss in the pipe is given by, = 0 001243 850 = 1 06 The buried vertical well cluster has three elbows and one tee. The hl,minor for the elbow is given by, ( ) = 0 3 1 015 2 2 32 2 = 0 0048 The hl,minor for the tee is given by, ( ) = 0 2 1 015 2 2 32 2 = 0 00 32 The total head for the buried well cluster F is given by, = 1 06 + 3 0 0048 + 0 0032 = 1 07

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112 Using the above equations and assumptions the head loss due to friction in the pipe was calculated for all the well clusters and is shown in Table B 1 Table B 1. Total head loss of the leachate in a pipe due to friction Buried well cluster Length of pipe (ft) hl due to friction in the pipe (ft) hl,minor Elbow (ft) hl,minor Tees (ft) Total head loss (ft) F 850 1.06 0.014 0.003 1.07 D 550 0.68 0.010 0.003 0.7 0 B 350 0.43 0.010 0.003 0.45 E 750 0.93 0.010 0.003 0.94 C 550 0.68 0.010 0.003 0.70 B 350 0.43 0.010 0.003 0.45

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113 APPENDIX C PRESSURE AND TEMPERA TURE DATA OF THE BUR IED VERTICAL WELL CLUSTERS VW piezometers were placed in the bottom of the first a nd last vertical well in the six cluster s to measure pressure and temperature in the well during leachate recirculation to evaluate the performance of various vertical well clusters. Figures in this appendix show pressure and temperature of all the working piezometers. Days 0 20 40 60 80 100 120 140 160 Pressure (m of H 2 0) 0 5 10 15 20 25 30 Temperature (C) -20 0 20 40 60 Pressure (6m deep cluster) Temperature (6m deep cluster) Day 1 = 11-11-08 Figure C 1. Change in pressure and temperature at the bottom of the first vertical well in the 6m well depth cluster of section I due to leachate recirculation

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114 Days 0 20 40 60 80 100 120 140 160 Pressure (m of H 2 0) 0 5 10 15 20 25 30 Temperature (C) -20 0 20 40 60 Pressure (6m deep cluster) Temperature (6m deep cluster) Day 1 = 11-11-08 Figure C 2. Change in pressure and temperature at the bottom of the last ver tical well in the 6m well depth cluster of section I due to leachate recirculation Days 0 20 40 60 80 100 120 140 160 Pressure (m of H 2 0) 0 5 10 15 20 25 30 Temperature (C) -20 0 20 40 60 Pressure (9m deep cluster) Temperature (9m deep cluster) Day 1 = 11-11-08 Figure C 3. Change in pressure and temperature at the bottom of the first vertical well in the 9m well depth cluster of section I due to leachate recirculation

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115 Days 0 20 40 60 80 100 120 140 160 Pressure (m of H 2 0) 0 5 10 15 20 25 30 Temperature (C) -20 0 20 40 60 Pressure (12m deep cluster) Temperature (12m deep cluster) Day 1 = 11-11-08 Figure C 4. Change in pressure and temperature at the bottom of the first vertical well in the 12m well depth cluster of section I due to leachate recirculation Days 0 20 40 60 80 100 120 140 160 Pressure (m of H 2 0) 0 5 10 15 20 25 30 Temperature (C) -20 0 20 40 60 Pressure (6m deep cluster) Temperature (6m deep cluster) Day 1 = 11-11-08 Figure C 5. Change in pressure and temperature at the bottom of the first vertical well in the 6m well depth cluster of section II due to leachate recirculation

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116 Days 0 20 40 60 80 100 120 140 160 Pressure (m of H 2 0) 0 5 10 15 20 25 30 Temperature (C) -20 0 20 40 60 Pressure (9m deep cluster) Temperature (9m deep cluster) Day 1 = 11-11-08 Figure C 6. Change in pressure and temperature at the bottom of the last vertical well in the 9m well depth cluster of section II due to leachate recirculation Days 0 20 40 60 80 100 120 140 160 Pressure (m of H 2 0) 0 5 10 15 20 25 30 Temperature (C) -20 0 20 40 60 Pressure (12 m deep cluster) Temperature (12m deep cluster) Day 1 = 11-11-08 Figure C 7. Change in pressure and temperature at the bottom of the first vertical well in the 12m well depth cluster of section II due to leachate recirculation

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117 Days 0 20 40 60 80 100 120 140 160 Pressure (m of H 2 0) 0 5 10 15 20 25 30 Temperature (C) -20 0 20 40 60 Pressure (12m deep cluster) Temperature (12m deep cluster) Day 1 = 11-11-08 Figure C 8. Change in pressure and temperature at the bottom of the last vertical well in the 12m well depth cluster of secti on II due to leachate recirculation

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118 APPENDIX D CONSTRUCTION PHOTOS OF THE EXPERIMENTAL SETUP TO MEASURE POR E PRESSURE DISTRIBUTIO N IN A LANDFILL Figure D 1. Hollow stem openflight auger being used for drilling Figure D 2. Assembling part of multilevel piezometer assembly 20 cm ho llow stem open flight auger Custom designed tail bit 20 cm bore hole

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119 Figure D 3. Installation of the multilevel piezometer in the borehole with a crane Figure D 4. Grouting of Multi level VW piezometer assembly Grout pipe

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120 APPENDIX E EXPERIMENTAL SETUP A ND RESULTS TO DETERM INE THE HYDRODYNAMIC LAG TIME OF PIEZOMETERS ENCASED IN GROUT A multilevel VW piezometer assembly using the groutedin installation method is typically used to measure pore water pressure at various depths in saturated soil and rock. However the waste in a landfill is generally unsaturated. A crucial parameter for the success of the fully grouted method for landfill application is the permeability of the cement bentonite grout (Contreras et al. 2008). Grout is a highly porous solid with a low permeability that lies somewhere i n the cement and Bentonite range, from 1x105 to 1x109 cm/sec. Hence there is a time lag associated with the liquids movements in an unsaturated grout medium. So an experiment was conducted in the lab to determine hydrodynamic lag time in reading the pore water pressure by the VW piezometer encased in grout due to transition from unsaturated to saturated state of grout Also when these piezometer assemblies were placed in the waste of the NRRL landfill, gas pressure s as high as 7 7.5 m of w.c. were observ ed. Since such high gas pressures have not been reported in literature, o ne possibility was that the high pore pressure could be due to the presence of the water that was initially added to prepare the grout. So the above experiment was used to determine the time taken by the water in the grout to completely dissipate in the surrounding sand media A single lysimeter column with a VW piezometer was used in this experiment. This column was a 6 feet long PVC column with an internal diameter of 10 inches as s hown in Figure E 1. On the side of this column there were two ports on the top and bottom of the column for inlet or outlet of water. There was a water level indicator on the side of this column to measure the water level inside the column. A four inch dia meter perforated PVC pipe was placed inside and concentric to the lysimeter column. Inside the perforated PVC pipe was a VW piezometer

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121 placed inside, concentric and at the bottom of the pipe. The volume between the perforated pipe and the inner diameter of the lysimeter column was filled with sand. The volume inside the perforated PVC pipe was filled with grout. The VW piezometer was connected to a handheld device Geokon to read frequency which was then converted into pressure using the linear equation give n in the calibration sheet by Geokon. 25 cm VW Piezometer 1.8 m10 cm Grout Readout device Sand Slotted PVC pipe Water level indicator Water inlet/outlet Water inlet/outlet Figure E 1. Experimental set up to determine the hydrodynamic lag time in reading the pore water pressure by a VW piezometer encased in grout The grout mixture was prepared by mixing cement, water and bentonite in the ratio of 1:6.6:0.4 respectively as prescribed by slope indicator The grout was then poured inside the perforated PVC pipe of the column. The pore pressure measured by the VW piezometer as a function of time was monitored continuously until the water in the grout dried and is shown in Figure E 2. It was found that the grout took around 22 days to full y dissipate the water in the surrounding sand media. The piezometer showed no pore water pressure after 22 day. This

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122 indicates that the gas pressure in the landfill was not due to the addition of water to prepare the grout Days 0 5 10 15 20 Pore water pressure (inch of H 2 0) 0 20 40 60 Figure E 2. Time taken by the piezometer to fully dissipate the water that was used to make the grout mixture to the surrounding sand media Water was added from the bottom of the lysim eter column and was raised by 10 12 inches at regular intervals. The level of water column and the pressure measured by the VW piezometer were monitored continuously between each interval. Table E 1 indicates that the hydrodynamic lag time of 24 48 hours a ssociated with reading the correct pore water pressure measured by the piezometer encased in grout due to transition from unsaturated to saturated state of grout due to liquids addition. However, once the surrounding grout gets saturated in water the hydrodynamic lag time varies from se conds to several minutes on the piezometer after a pressure change (McKenna 1995, Mikkelsen 2002, and Mikkelsen et al. 2003). The piezometer tips only require a small equalization volume (102 to 105 cm3) and the saturated grout can quickly transmit this volume over the short distance between the formation and the piezometer cavity (McKenna 1995).

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123 Table E 1. H ydrodynamic lag time in reading the pore water pressure by the VW piezometer encased in grout due to transition from unsaturated to saturated media as a result of leachate addition Applied water head in the column (inch of H2O) Pore water pressure measured by the VW piezometer (inch of H2O) Hydrodynamic lag time (hr) 7.6 8.1 46.3 10.75 11.14 25.15 14.3 14.7 27.15

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124 APPENDIX F UNIT CONVERSION AND NORMAILIZATION OF VW PIEZOMETERS F .1 Calculation to Convert Pore Pressure Measured i n Frequency to Units of Pressure Readings from the Slope Indicator VW piezometers are in Hertz, rather than in units of pressure. To conver t the Hertz reading to units of pressure, factors listed on the sensor calibration record is applied. The following equation was provided by slope indicator. Pressure = A Hz2 + B Hz + C Where Hz is the frequency reading in Hertz, and A, B, and C are the factors on the sensor calibration record provided by Slope indicator A = 0.0000092433, B= 0.018787, C = 151.31 For example, F requency of A1 = 3149.9 Hz = 0 0000092433 3149 9 2 + ( 0 018787 ) 3149 9 + 151 31 = 0.422 m of H2O Therefore, the pore pressure measured by the piezometer A1 is 0.422 m of H2O. F .2 Normalization of Pore Pressure Data of a Piezometer The Figure G 1 presents the example of pressure data measured by a piezometer A2 over time. The initial reading from the piezometer was taken on day 506 just prior to installation of the piezometer i n the waste. After installing the piezometer inside the landfill, the pore pressure rapidly increased due to the pressure of landfill gas inside the waste. Prior to leachate injection the pore pressure in the waste was close to 2 m of w.c. as shown in Fig ure G 2. In order to see the impact of leachate injection into the buried vertical wells on the pore water pressure in the surrounding waste, the piezometers were normalized to zero just prior to liquids injection Th is

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125 was done by subtracting the pore pre ssure reading just before injecting leachate for the first time. The normalized pressure data for the piezometer A2 is shown in Figure G 3. Days (1311 = 12-1-09) 600 800 1000 1200 1400 Pressure (m of w.c.) 0 2 4 6 8 10 Pressure Day 1313 = 12-3-09 (1st day of leachate reciruclation) Figure F 1. Pore pressure data measured the piezometer since calibration by the manufacturer Days (1311 = 12-1-09) 1320 1340 1360 1380 1400 1420 1440 1460 Pore water pressure (m of w.c.) 0 2 4 6 8 10 Pressure Day 1313 = 12-3-09 (1st day of leachate reciruclation) Figure F 2. Actual pore pressure measured a VW piezometer since starting leachate addition on day 1313

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126 Days 1320 1340 1360 1380 1400 1420 1440 1460 Pore water pressure (m of w.c.) 0 2 4 6 8 Pressure Day 1313 = 12-3-09 (1st day of leachate reciruclation) Figure F 3. Normalized pore pressure measured a VW piezometer since starting leachate addition on day 1313 F.3 Example of Piezometers not Considered for Analysis A total of 58 piezometers worked properly out of the 90 piezometers installed in the multi level piezometers A total of 13 piezometers stopped working immediately after installation and 19 piezometers either stopped working or started giving highly erratic and f luctuating data during the course of two years. An example of a piezometer that was not considered for interpretation of results due to highly erratic and fluctuating pore water pressure data is shown in Figure F 4.

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127 Days 1320 1340 1360 1380 1400 1420 1440 1460 Pore water pressure (m of w.c.) -5 0 5 10 15 Day 1313 = 12-3-09 (1st day of leachate reciruclation) Figure F 4. An example of a VW piezome ter that was not considered for interpretation of results due to highly erratic and fluctuating pore water pressure data

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128 APPENDIX G PORE PRESSURE AND TE MPERATURE OF INDIVID UAL PIEZOMETERS Several piezometers surrounding a buried vertical well were instal led i s to examine the temporal and spatial impact of leachate recirculation into wells on the pore water pressure in the surrounding waste in a full scale MSW landfill. The figures in this appendix shows the pore pressure and temperature data for all the w orking piezometers. Data for each piezometer is indicated by three Figures. The first Figure (a) presents the pore pressure over time from the day of calibration. The second Figure (b) presents the normalized pore pressure over time from the beginning of l eachate recirculation The third Figure (c) presents the normalized pore pressure during the initial days of leachate injection .

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129 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 40 45 50 55 60 65 70 Pressure Temperature Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature Piezometer Name: A1 Depth from the surface of the landfill: 5.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Figure G 1. Pore pressure and temperature data of piezometer A1 : (a) Pore pressure over time from the calib ration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

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130 Piezometer Name: A2 Depth from the surface of the landfill: 8.8m Start day and da te of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 40 45 50 55 60 65 70 75 Pressure Temperature Figure G 2. Pore pressure and temperature data of piezometer A2 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

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131 Piezometer Name: A4 Depth from the surface of the landfill: 14.9m Start day and date of leachate recirculati on: 1313 = 123 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -50 0 50 100 150 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 40 50 60 70 Pressure Temperature Figure G 3. Pore pressure and temperature data of piezometer A4 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

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132 Piezometer Name: B1 Depth from the surface of the landfill: 5.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -4 -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 40 45 50 55 60 65 70 Pressure Temperature Figure G 4. Pore pressure and temperature data of piezometer B1 : (a) Pore pr essure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 132

133 Piezometer Name: B2 Depth from the surface of the l andfill: 8.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -4 -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 40 45 50 55 60 65 70 75 Pressure Temperature Figure G 5. Pore pressure and temperature data o f piezometer B2 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 133

134 Piezometer Name: B3 Dep th from the surface of the landfill: 11.9m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 40 45 50 55 60 65 70 75 Pressure Temperature Figure G 6. Pore pre ssure and temperature data of piezometer B3 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injecti on. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 134

135 Piezometer Name: B4 Depth from the surface of the landfill: 14.9 m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 40 45 50 55 60 65 Pressure Temperature Figure G 7. Pore pressure and temperature data of piezometer B4 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the in itial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 135

136 Piezometer Name: B5 Depth from the surface of the landfill: 18m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection p ressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -50 0 50 100 150 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 40 60 80 100 120 140 Pressure Temperature Figure G 8. Pore pressure and temperature data of piezometer B5: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 136

137 Piezometer Name: C1 Depth from the surface of the landfill: 5.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 40 45 50 55 60 65 70 Pressure Temperature Figure G 9. Pore pressure and temperature data of piezometer C1 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate r ecirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 137

138 Piezometer Name: C2 Depth from the surface of the landfill: 8.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 40 45 50 55 60 65 70 75 Pressure Temperature Figure G 10. Pore pressure and temperature data of piezometer C2 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

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139 Piezometer Name: C3 Depth from the surface of the landfill: 11.9m Start day and date of leachate recirculation: 1313 = 12 3 09 Period o f leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 40 45 50 55 60 65 70 75 Pressure Temperature Figure G 11. Pore pressure and temperature data of piezometer C3 : (a) Pore pressure over time from the calibration day, (b) Normali zed pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 139

140 Piezometer Name: C5 Depth from the surface of the landfill: 18m Start day and date of leachate recirculat ion: 1313 = 123 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 100 120 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 12. Pore pressure and temperature data of piezometer C5: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 140

141 Piezometer Name: D1 Depth from the surface of the landfill: 5.8m Start day a nd date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 Pressure Temperature Figure G 13. Pore pressure and temperature data of piezometer D1 : (a) Por e pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 141

142 Piezometer Name: D3 Depth from the surface of t he landfill: 11.9m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 Pressure Temperature Figure G 14. Pore pressure and temperature data of piezometer D3: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 142

143 Piezometer Name: D 5 Depth from the surface of the landfill: 18m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 15. P ore pressure and temperature data of piezometer D5 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 143

144 Piezometer Name: G1 Depth from the surface of the landfill: 5.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -4 -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) -1 0 1 2 3 Temperature (C) 20 30 40 50 60 70 Pressure Temperature Figure G 16. Pore pressure and temperature data of piezometer G1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 144

145 Piezometer Name: G2 Depth from the surface of the landfill: 5.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 17. Pore pressure and temperature data of piezometer G2 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) No rmalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 145

146 Piezometer Name: G5 Depth from the surface of the landfill: 18m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 Pressure Temperature Figure G 18. Pore pressure and temperature data of piezometer G5: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 146

147 Piezometer Name: H3 Depth from the surface of the landfill: 11.9m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculati on: 1313 to 1434 (123 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -50 0 50 100 150 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 40 60 80 100 120 140 Pressure Temperature Figure G 19. Pore pressure and temperature data of piezometer H3: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 147

148 Piezometer Name: E1 Depth from the surface of the landfill: 5.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -4 -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 Pressure Temperature Figure G 20. Pore pressure and temperature data of piezometer E1 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 148

149 Piezometer Name: E2 Depth from the surface of the landfill: 8.8m Start day and date of leachate recirculation: 1313 = 123 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 21. Pore pressure and temperature data of piezometer E2 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 149

150 Piezometer Name: F1 Depth from the surface of the landfill: 5.8m St art day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -4 -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) -1 0 1 2 3 Temperature (C) 20 30 40 50 60 70 Pressure Temperature Figure G 22. Pore pressure and temperature data of piezometer F1 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 150

151 Piezometer Name: F3 Depth from the sur face of the landfill: 8.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 23. Pore pressure and temperature data of piezometer F3 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 151

152 Piezomete r Name: F5 Depth from the surface of the landfill: 5.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 25 30 35 40 45 Pressure Temperature Figure G 24. Pore pressure and temperature data of piezometer F5 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of l eachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 152

153 Piezometer Name: I1 Depth from the surface of the landfill: 5.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.38 2.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) -1 0 1 2 3 Temperature (C) 20 30 40 50 60 70 Pressure Temperature Figure G 25. Pore pressure and temperature data of piezometer I1 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 153

154 Piezometer Name: I2 Depth from the surface of the landfill: 8.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 22 Pressure Temperature Figure G 26. Pore pressure and temperature data of piezometer I2 : (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 154

155 Piezometer Name: I3 Depth from the surface of the landfill: 11.9m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 27. Pore pressure and temperature data of piezometer I3: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginni ng of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 155

156 P iezometer Name: I4 Depth from the surface of the landfill: 14.9m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (123 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 Pressure Temperature Figure G 28. Pore pressure and temperature data of piezometer I4: (a) Pore pressure over time from the calibration day, (b) Normalized pore pres sure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 156

157 Piezometer Name: J2 Depth from the surface of the landfill: 8.8m Start day and date of leachate recirculation: 1313 = 123 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 29. Pore pressure and temperature data of piezometer J2: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 157

158 Piezometer Name: K1 Depth from the surface of the landfill: 5.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 Pressure Temperature Figure G 30. Pore pressure and temperature data of piezometer K1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 158

159 Piezometer Name: K2 Depth from the surface of the landfill : 5.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 31. Pore pressure and temperature data of piez ometer K2: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 159

160 Piezometer Name: L1 Depth fr om the surface of the landfill: 5.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 Pressure Temperature Figure G 32. Pore pressur e and temperature data of piezometer L1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 160

161 Piezometer Name: L2 Depth from the surface of the landfill: 8.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 33. Pore pressure and temperature data of piezometer L2: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 161

162 Piezometer Name: L3 Depth from the surface of the landfill: 11.9m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 34. Pore pressure and temperature data of piezometer L3: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 162

163 Piezometer Name: L4 Depth from the surface of the landfill: 14.9m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 Pressure Temperature Figure G 35. Pore pressure and temperature data of piezometer L4: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 163

164 Piezometer Name: L5 Depth from the surface of the landfill: 18.0m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 13 13 to 1434 (123 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 Pressure Temperature Figure G 36. Pore pressure and temperature data of piezometer L5: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 164

165 Piezometer Name: M2 Depth from the surface of the landfill: 8.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 37. Pore pressure and temperature data of piezometer M2: (a) Pore pressure over time from the calibration day, (b) Norma lized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 165

166 Piezometer Name: M3 Depth from the surface of the landfill: 11.9m Start day and date of leachate recir culation: 1313 = 123 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 100 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 38. Pore pressure and temperature data of piezometer M3: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 166

167 Piezometer Name: O1 Depth from the surface of the landfill: 5.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -4 -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 39. Pore pressure and temperature data of piezometer O1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 167

168 Piezometer Name: O2 Depth from the surface of the landfill: 8.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 40. Pore pressure and temperat ure data of piezometer O2: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 168

169 Piezometer Name: O3 Depth from the surface of the landfill: 11.9m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 41. Pore pressure and temperature data of piezometer O3: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of le achate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 169

170 Piezometer Name: Q4 Depth from the surface of the landfill: 14.9m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.38 2.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 25 Pressure Temperature Figure G 42. Pore pressure and temperature data of piezometer Q4: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 170

171 Piezometer Name: Q5 Depth from the surface of the landfill: 18m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leach ate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 25 30 35 40 45 50 55 Pressure Temperature Figure G 43. Pore pressure and temperature data of piezometer Q5: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 171

172 Piezometer Name: P1 Depth from the surface of the landfill: 5.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -4 -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 44. Pore pressure and temperature data of piezometer P1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

PAGE 172

173 Piezometer Name: P2 Depth from the surface of the landfill: 8.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (123 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 100 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 90 Pressure Temperature Figure G 45. Pore pressure and temperature data of piezometer P2: (a) Pore pressure over time from the calibration day, (b) Normalized pore pres sure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

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174 Piezometer Name: P3 Depth from the surface of the landfill: 11.9m Start day and date of leachate recirculation: 1313 = 123 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 46. Pore pressure and temperature data of piezometer P3: (a) Pore pressure over time from the calibratio n day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

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175 Piezometer Name: P4 Depth from the surface of the landfill: 14.9m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 Pressure Temperature Figure G 47. Pore pressure and temperature data of piezometer P4: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

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176 Piezometer Name: P5 Depth from the surface of the landfil l: 18m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 Pressure Temperature Figure G 48. Pore pressure and temperature data of pie zometer P5: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

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177 Piezometer Name: R1 Depth fr om the surface of the landfill: 5.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 49. Pore pressure and temperature data of piezometer R1: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

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178 Piezometer Name: R2 Depth from the surface of the landfill: 8.8m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 70 80 Pressure Temperature Figure G 50. Pore pressure and temperature data of piezometer R2: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initi al days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

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179 Piezometer Name: R3 Depth from the surface of the landfill: 11.9m Start day and date of leachate recirculation: 1313 = 12 3 09 Period of leachate recirculation: 1313 to 1434 (12 3 09 to 43 09) Average leachate injection pressure: 15.382.4 m of w.c Days (1 = 5-1-05) 0 600 800 1000 1200 1400 Pore pressure (m of W.C.) -2 0 2 4 6 8 10 12 14 Temperature (C) -40 -20 0 20 40 60 80 Pore pressure Temperature 1320 1340 1360 1380 1400 1420 1440 1460 Normalized pore pressure (m of w.c.) 0 2 4 6 8 10 12 14 Temperature (C) -60 -40 -20 0 20 40 60 80 Pressure Temperature Days (1311 = 12-1-09) 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 Normalized pore pressure (m of w.c.) 0 1 2 3 Temperature (C) 20 30 40 50 60 Pressure Temperature Figure G 51. Pore pressure and temperature data of piezometer R3: (a) Pore pressure over time from the calibration day, (b) Normalized pore pressure over time from the beginning of leachate recirculation, (c) Normalized pore pressure during the initial days of leachate injection. Q N R P O M L J A C I F B K G D H E LIW 7.6 m 1.5 m = LIW: Leachate injection well = A to R: Multi-level piezometer wells (a) (b) (c)

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180 APPENDIX H ESTIMATION OF POTENT IAL PORE PRESSURE DI STRIBUTION IN A LAND FILL The steady state one dimensional analytical gas model developed by Townsend et al. (2005) was used to predict the pote ntial pore pressure distribution in cell 4 of the NRRL landfill. This model allows evaluation of scenarios where gas is extracted using a combination of a landfills leachate collection system (LCS) and surface capping system. The gas model assumes that the permeability of waste is uniform in the landfill and the gas generation rate does not vary with time. The waste in cell 4 was temporarily capped in 2006. So the waste can be treated as fresh. A gas generation rate of 4.8 108 kg/m3.sec was selected to represent rapidly decomposable dry waste for the model and was based on a study conducted by De Walle et al. (1978). The Figure H 1 shows the gas pressure distribution within the landfill for different permeability of waste. For this scenario, the gas pressure at the surface of the landfill was assumed to be atmospheric and no gas was collected from the LCS. Results indicated that high gas pressures within the landfill were caused by a lower permeability of waste. Air injection test conducted by Jain et al (2005) at the NRRL landfill indicated that similar lower permeability of waste was found in the deeper sections of the landfill. Figure H 2 shows the gas pressure distribution within in the landfill for different gas collection rates for the leachate co llection system. The surface of the landfill was assumed to be atmospheric. Results indicated that maximum gas pressure was realized in the center of the landfill when both the surface of the landfill and the leachate collection system was subjected to the atmospheric pressure. However, the gas pressures within the landfill as shown in Figure 34 increased with increase in the depth of the landfill. This could be due a decrease in permeability with increase in the depth of the landfill as opposed to uniform permeability throughout the landfill assumed by the gas model.

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181 Pore pressure in the landfill (m of w.c.) 0 2 4 6 8 10 Depth of the landfill (m) 0 5 10 15 20 k z = 3.2 x 10 -11 m 2 k z = 1.0 x 10 -12 m 2 k z = 5.0 x 10 -13 m 2 k z = 2.5 x 10 -13 m 2 k z = 1.6 x 10 -13 m 2 Figure H 1. Gas pressure distribution within in the landfill for different permeability of waste Pore pressure in the landfill (m of w.c.) 0 2 4 6 8 10 Depth of the landfill (m) 0 5 10 15 20 = 0.5ML = 0.25ML = 0.0ML Figure H 2. Gas pressure distribution within in the landfill for different gas collection rates for the leachate collection system

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182 APPENDIX I SUPPLEMENTAL FIGURES AND GRAPHS TO DETERM INE SETTLEMENT IN A BIOREACTOR LANDFILL DUE TO MOISTURE ADDI TION F igure I 1. Plan view showing the location of injection clusters (Adapted from as built drawings provided by Jones Edmunds and Associates) Anaerobic Aerobic A A B B C C Boundary of the bioreactor

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183 0 10 20 30 40 50 60 70 80 90 -10 0 10 20 30 40 50 60 70 80 0 10 20 30 40 50 60 70 80 90 -10 0 10 20 30 40 50 60 70 80 16 16.9 17.8 18.7 19.6 20.5 21.4 22.3 23.2Distance (m)Distance (m)Elevation (m)(a) Before leachate recirculation (2002)(b) After leachate recirculation (2007) Figure I 2. Elevation contours of the bioreactor landfill in 2002 and 2007

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184 Section 1 S= 11.67 M= 163k Section 5 S= 12.81 M=375k Section 9 S= 13.75 M=310k Section 13 S= 11.71 M=365k C ell 2 Section 2 S= 10.02 M=238k Section 6 S= 11.82 M=488k Section 10 S= 12.74 M=612k Section 14 S= 11.87 M=384k Section 3 S= 8.83 M=23k Section 7 S= 11.14 M=154k Section 11 S= 11.75 M=460k Section 15 S= 11.66 M=485k Section 4 S= 9.11 M=108k Section 8 S= 9.45 M=366k Section 12 S= 11.41 M=576k Section 16 S= 12.54 M=467k Cell 4 Figure I 3. Schematic diagram of various sections of the bioreactor area along the corresponding settlement % and the amount of liquids injected S = % Settlement M = Gallons of leachate injected k = 1000 gallons

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185 (a) Top layer (b) Upper middle layer (c) Lower middle layer (d) Bottom layer Figure I 4. Percentage Settlement vs. moisture content in various layers of a landfill Top layer (0-5.23 m) Moisture Content (%) 30 35 40 45 50 55 60 Settlement (%) 4 6 8 10 12 14 16 Second layer from the top (5.23-9.67m) Moisture Content (%) 30 35 40 45 50 55 60 Settlement (%) 4 6 8 10 12 14 16 Third layer from the top (9.67-14.29m) Moisture Content (%) 30 35 40 45 50 55 60 Settlement (%) 4 6 8 10 12 14 16 Bottom layer (14.29-18.81m) Moisture Content (%) 30 35 40 45 50 55 60 Settlement (%) 4 6 8 10 12 14 16 18

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186 Various depths in the landfill (ft) 0-10 15-25 30-40 Moisture content (%) 0 10 20 30 40 50 60 70 Figure I 5 Moisture content at different depths in the bioreactor area of the landfill in 2007

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187 APPENDIX J ESTIMATION OF PREDIC TED SETTLEMENT Settlement due to leachate recirculation in a bioreactor landfill was predicted by calculating the mechanical settlement caused by the overburden pressure of the liquids added and biological settlement c aused by waste decomposition. Mechanical Settlement: The settlement due to overburden pressure of the leachate in a bioreactor landfill was calculated using the compression indices and equation developed by McKnight (2005). ----------------------(1) Where, St = Settlement due to overburden pressure of the leachate added in the waste layer Ht 1 = Initial height of the waste layers t 1 = Effective overburden pressure due to waste only = Effective overburden pressure due to waste and leachate ct and ct 1 = Compression index (unit less) The Figure N 1 shows a vertical well cluster and the four layers of waste. The settlement would occur in the bottom three layers of the waste due to the overburden pressure of leachate acting on top of these layers. The following assumptions were made prior to calculating the mechanical settlement acting on these layers. In this assumputions typical values used for landfill construction were employed. Unit weight of waste = 770 kg/m3 Unit weight of cover soil = 1840 kg/m3 = 1 1 1 1

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188 Co ver soil (%) by volume of landfill = 13 Compression index (ct and ct 1) = 0.2 Equation 1 was used to calculate the settlement occurring in the various layers of the landfill as shown in Table N 1. The total mechanical settlement was obtained by adding th e settlement in all the layers of the waste and was 0.57 m. Initial height of the landfill was 21.9m. Hence, the mechanical settlement percentage = (0.57 21.9) 100 = 2.6% of the initial height. Table J 1. Mechanical settlement occurring in the various layers of the landfill due to the overburden pressure of the leachate addition Thickness of the layer Volume of leachate Weight of leachate Stress due to leachate Height of the waste above the layer t 1 t St (m) (m3) x 106(kg) (kg/m2) (m) (kg/m2) (kg/ m2) (m) 5.06 11952 12 1195 5.4 4933 6128 0.21 5.11 17902 18 1790 10.5 9538 11328 0.17 6.31 22712 23 2271 15.6 14188 16459 0.18 Biological Settlement: The average of waste decomposition rates (k) of NRRL between 2001 and 2007 was 0.23 year1 (Townsend et al. 2009). The first order relationship that models the conversion of waste mass into landfill gas is shown in the equation below Where, MBVS,o is the original mass of waste ultimately converted to gas, t is the time, and k is the first order decay r ate [t1]. Assuming the mass of biodegradable volatile solids to be 1 in 2002, the mass of biodegradable volatile solids in 2007 is given by, MBVS,t = 1 e0.23 5 = 0.3166 The biodegradable fraction of volatile solids that degraded was = (1 0.3166) 100 = 68.34 % kt o BVS t BVSe M M, ,

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189 Assuming that the waste had the following initial composition in 2002 Volatile solids content: 77.2 % Biodegradable fraction (% of volatile solids): 57.8% Cover soil in the waste: 13% Specific weight of the waste: 771 kg/m3 Thus, the fracti on of waste lost from 2002 until 2007 is given by, = 68.34 0.578 0.772 = 30.49 % The volume of the bioreactor based on the defined boundary area as mentioned in the chapter was 177,080 m3. Assuming that the cover soil content was 13%, the volume occupied by the waste in 2002 is given by, = 0.87 177,080 m3 = 154,096 m3 The weight of waste in 2002 is given by, = 771 kg/m3 154,096 m3 = 118,779,951.6 kg The weight of waste lost from 2002 until 2007 is given by, = 118,779,951.6 kg 0.3049 = 36,216,007.24 kg The weight of the waste left in 2007 = 118,779,951.6 kg 36,216,007.24 kg = 82,563,944.36 kg The volume of the waste in 2007 = 82,563,944.36 kg 771 kg/m3 =107086 m3 The volume of the landfill in 2007 = 107,086 m3 0.87 = 123087 m3

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190 Therefore, the decrease in volume of the bioreactor from 2002 to 2007, = 177080 m3 123087 m3 = 53992.64 m3 The area of the bioreactor was 10,000 m2. Hence the settlement in the bioreactor due to biological settlement was = 53,992.6 10,000 = 5.39 m. The initial height of the bioreactor is 21.9 m. Hence the biological settlement percentage = (5.39 21.9) 100 = 24.6% of the initial height. The total predicted settlement was obtained by adding the mechanical and biol ogical settlement. Therefore, the predicted settlement = 2.6 + 24.6 = 27.2% of the initial height. Figure J 1. Leachate added in the various layers of the landfill

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191 LIST OF REFERENCES Barber, C. and Maris, P.J. (1984). Recirculation of leachate as a landfill management option: benefits and operational problems. Quarterly Journal of Engineering Geology London, 17, 1929. Benson, C. H., Barlaz, M. A., Lane, D. T., and Rawe, J. M., B.E. (2007) Practice review of five bioreactor/recirculation landfills. Waste Management 27,1329. Bowders, J., Mouzza, M., and Russell, M., ( 2000) Settlement of municipal solid waste landfills. 4th Kansai Intl Geotechnical Forum Buivid, M.G., Wise D.L., Blanchet M.J., Remedios E.C., Jenkins B.M., Boyd W.F. and Pac ey, J.G. (1981). Fuel gas enhancement by controlled landfilling of municipal solid waste. Resources and Conservation 6, 320. Chamil H. Hettiarachchi, Jay N. Meegoda, John Tavantzis, Patrick Hettiaratchi, ( 2007) Numerical model to predict settlements c oupled with landfill gas pressure in bioreactor landfills. Journal of Hazardous Materials B139, 514522. Dean K. Wall, and Chris Zeiss, ( 1995 ) Municipal landfill biodegradation and settlement. Journal of Environmental Engineering, Vol. 121, No. 3. Du rmusoglu, M., Corapcioglu, Y., and Tuncay, K., ( 2005) Landfill settlement with decomposition and gas generation. Journal of Environmental Engineering, Vol. 131, No. 9. El Fadel, M. (1999). Leachate recirculation effects on settlement and biodegradation rates in MSW landfills. Environmental Technology 20, 12133. Gonzalez Garcia, A. J., and Espinosa Silva, A. (2003). "Doa Juana sanitary landfill catastrophic failure in 1997Bogot, Colombia." Proc., 12th Panamerican Conf. on Soil Mechanics and Geotechnical Engineering, VGE, Essen, Germany, Vol. 2, 13531360. Grosser, C., and Strate, V., ( 2008) ," The Use of the Fully grouted Method for Piezometer Inst allation Geotechnical News 26, 30 37. Haydar, M.,and Khire, M. (2005), Leachate Recirculation Using Horizontal Trenches in Bioreactor Landfills, Journal of Geotechnical & Geoenvironmental Engineering, American Society of Civil Engineers, Vol. 131, No. 7, 837847. Haydar, M. M., and Khire, M. V. (2007). Leachate recirculation using permeable blankets in engineered landfills. J. Geotech. Geoenviron. Eng., 133, 2, 166174. Hendron, D. M., Fernandes, G., Prommer, P. J., Giroud, J. P., and Orozco, L. F. (1999). "Investigation of the cause of the 27September, 1997 slope failure at the Doa Juana landfill." Proc., Sardinia 1999: 7th Int. Waste Management and Landfill Symp., CISA, Cagliari Italy, 545554.

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192 Hossain, M. A. Gabr, M.A. and Barlaz, ( 2003) Relationship of compressibility parameters to municipal solid waste decomposition., Journal of Geotechnical and Geoenvironmental Engineering, Vol. 129, No. 12. Hossain S.D. and Haque Mohamed A.(2009). The effects of daily cover soils on shear strength of municipal solid waste in bioreactor landfills, Waste Management 29, 1568157 Jain, P. (2005). Moisture addition at bioreactor landfills using vertical wells: Mathematical modeling and field application Ph.D. Dissertation. University of Florida, Gainesville, FL, USA. Jain, P., Farfour, W. M., Jonnalagadda, S., Townsend, T. G., and Reinhart, D. R. (2005a). Performance evaluation of vertical wells for landfill leachate recirculation. Proceedings of Geo Frontier 2005, ASCE conference, January 2426, Austin, TX, USA. Jain, P., Larson, J., Townsend, T.G. and Tolaymat, T. (2007). Design of vertical wells for introduction at bioreactor landfill: Guidelines based on mathematical modeling Submitted to Journal of Environmental Engineering, ASCE. Jain, P., Powell, J. P., Townsend, T. G., and Reinhart, D. R. (2005b). Air permeability of waste in a municipal solid waste landfill. Journal of Environmental Engineering ASCE, 131(11) 15651573. Jain, P., Powell, J. P., Townsend, T. G., and Reinhart, D. R. (2006). Estimating the hydraulic conductivity of landfilled municipal solid waste using the borehole permeameter test. Journal of Environmental Engineering, ASCE, 132(6). 645652. Jonnalagadda, S. (2004). Resistivity and time domain reflectrometry sensors for a ssessinging in situ moisture content in a bioreactor landfill. Master's Thesis, University of Florida, Gainesville, FL, USA. Koerner, R. M., and Soong, T.Y. (2000). "Leachate in landfills: The stability issues." Geotext. Geomembr., 18 (5), 293 309. Leckie, J.D., Pacey, J.G. and Halvadakis C.P. (1979). Landfill management with moisture control., Journal of Environmental Engineering Division, ASCE EE2, 105, 337355. Ling, I., Leshchinsky, D., and Yoshiyuki M ,, ( 1998) Estimation of municipal solid waste l andfill settlement. Journal of Geotechnical and Geoenvironmental Engineering, Vol. 124, No. 1. Khire, M. and Mukherjee, M. (2006), Leachate Injection Using Vertical Wells in Engineered Landfills, Waste Management Elsevier in press.

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193 Landva, A. O., Pel key, S. G., and Valsangkar, A. J. (1998). Coefficient of permeability ofmunicipal refuse. Proceedings of the Third International Congress on Environmental Geotechnics Lisbon, Portugal, 16367. McCreanor, P.T. and Reinhart, D.R (1996). Hydrodynamic mode ling of leachate recirculating landfills. Wat Sci. Tech Vol. 34, No. 78, pp 463470. McCreanor, P.T. (1998). Landfill leachate recirculation systems: Mathematical modeling and validation Ph.D. Dissertation. University of Central Florida. McCreanor, P.T. and Reinhart, D.R. (2000) Mathematical Modeling of Leachate Routing in a Leachate Recirculating Landfill Wat. Res 2000, Vol. 34, No. 4, 12851295. McKenna, G.T, (1995),"Groutedin Installation of Piezometers in Boreholes," Geotechnical Journal, 32, 355363. Mehta, R., Barlaz, M.A., Yazdani, R., Augenstein, D., Bryars, M., and Sinderson, L. (2002) Refuse Decomposition in the Presence and Absence of Leachate Recirculation. Journal of Environmental Engineering, March 2002, 228236. Miller, D.E. and Emge, S.M. (1997). Enhancing landfill leachate recirculation system performance. Practice Periodical of Hazardous, Toxic, and Radioactive Waste Management, July 1997, 113119 Mikkelsen and Green, ( 2003) ," Piezometers in Fully Grouted Boreholes ." International ymposium on Geomechanics Oslo, Norway. September Natale, B.R. and Anderson W.C. (1985). Evaluation of a landfill with leachate recycle. Draft re port to USEPA Office of Solid Waste Washington, DC USA. Pacey, J. P., Ramin Yazdani, D. Reinhart, R. Morck, D. Augenstein (1999). The Bioreactor Landfill: An Innovation in Solid Waste Management., SWANA Silver Springs, Maryland. Park H. I. Park, B. Le e S. ( 2007) Analysis of long term settlement of municipal solid waste landfills as determined by various settlement estimation methods. Air & Waste Management Association, Vol. 57, 212218 Pohland, F.G. (1975). Sanitary landfill stablization with lea chate recycle and residual treatment. EPA 600/275043. USEPA, Washington DC, USA. Pohland, F.G. and Harper, S.R. (1986). Critical review and summary of leachate and gas production from landfills., EPA/600/286/073. Cincinnati, OH, U.S.A.: U.S. Environmental Protection agency. Ramin Yazdani, Jeff Kieffer, Kathy Sananikone, ( 2007) Controlled bioreactor landfill program at the Yolo County Central Landfill Methane to Markets Partnership Expo, Presentation.

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194 Reinhart, D.R., McCreanor, P.T., and Townsend, T.G. (2002). The bioreactor landfill: Its status and future. Waste Management and Research. 20: 172186 Reinhart, D. R. (1996). Full scale experiences with leachate recirculation landfills: Case studies. Waste Management and Research, 14(4), 347365. Rosqvist, H. & Destouni, G. (2000) Solute transport through preferential pathways in municipal solid waste. Journal of Contaminant Hydrology ,46, 3960. Simoni A., Berti M., Generali M., Elmi C., Ghirotti M. (2004). Preliminary results from pore pressu re monitoring on an unstable clay slope. Engineering Geology, 73, 117128. Smith M.C., Gatte D.K., Boothe D.D.H. and Das K.C. (2000). Enhancing Aerobic bioreduction under controlled conditions in a municipal solid waste landfill through the use of air i njection and water recirculation. Advances in Environmental Research, 3(4) 2000, 459471. Swati M. Kurian Joseph, ( 2008) Settlement analysis of fresh and partially stabilized municipal solid waste in simulated controlled dumps and bioreactor landfills., Waste Management 28, 13551363. Thiel, R. (1999). "Design of a gas pressure relief layer below a geomembrane cover to improve slope stability." Proc., Geosynthetics '99 Conf., Boston, Industrial Fabrics Association International St. Paul, Minn., Vol. 1, 235251. Townsend, T. G. (1995). Leachate recycle at solid waste landfills using horizontal injection. Ph.D. Dissertation, University of Florida, Gainesville, FL, USA. Townsend, T. G., Miller, W. L, Lee, H. J., and Earle, J. F. K (1996). Acceleration of landfill stabilization using leachate recycle. Journal of Environmental Engineering, ASCE, 122(4), 263268. Townsend, T.G., Jain, P. and Tolaymat, T. (2006). Liquid introduction design criteria for bioreactor landfills, US EPA Final report December 2006. US EPA (2007). Bioreactor Landfills June 2007 Vaughan, P. R ( 2001) "A Note on Sealing Piezometers in Boreholes," Geotechnique 19, 3, 405413. Warith, M. (2002). Bioreactor Landfills: experimental and field results. Waste Management 22 (2002) 717. Watson, R.P. (1987). "A case study of leachate generation and recycling at two sanitary landfills" in Proceedings from the Technical Sessions of the GRCDA 25th Annual International Seminar, Equipment, Services, and Systems Show. Vol. 1, August 1113,

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195 BIOGRAPHICAL SKETCH Ravi Sh ankar Kadambala was born on 1979, in Bhubaneshwar, India, to Adinarayana and Indira Kadambala. He enrolled in Shivaji University, Kolhapur, India in July, 1996, and graduated with a Bachelor of Engineering in Chemical Engine ering in May, 2000. He received his masters degree in Industrial Engineering from Florida State University, Tallahassee, Florida in December 2003.He worked as an engineer I with the Florida Department of E nvironmental Protection, Tallahassee, Florida for a year He continued his education by enroll ing in graduate program in the Department of Environmental Engineering Sciences at the University of Florida in June, 2005, to study solid and hazardous waste management under the guidance of Dr. Timothy Townsend. He has started working with CDM as an Environmental Engineer III since June 2009 at the West Palm Beach office in Florida.