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PLANNING DECISION FRAMEWORK FOR BRACKISH WATER AQUIFER,
STORAGE AND RECOVERY (ASR) PROJECTS
CHRISTOPHER J. BROWN
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
Christopher J. Brown
This document is dedicated to my wife, Laura J. Hansen-Brown, who has provided
inspiration and support throughout my 4 years at the University of Florida. Without
support from Laura Jean, none of this work would have been feasible. In addition, I
dedicate this work to my co-workers at the U. S. Army Corps of Engineers in
Jacksonville, Florida, who have supported me with flexibility and patience.
The preparation of a dissertation is a long and difficult process. It is only made
possible through support from many different persons. I would like to thank my wife,
Laura J. Hansen-Brown, for her unwavering support, love, and help through four long
years. I would like to thank my family members for their support. I would like to thank
my co-workers including Dr. Greg Whittle, Dr. Samir Itani, Mike Fies, Susan Sylvester,
Jeff Hendel, Steve Sutterfield, and Rebecca Weiss. I would like to extend thanks to my
supervisors at the U. S. Army Corps of Engineers in Jacksonville, including Mr. Luis
Ruiz, Mr. Randy Bush, and Mr. Steve Duba. I also am thankful for the technical advice
from co-workers and friends at the South Florida Water Management District.
I wish to acknowledge all researchers and scientists from around the world who
provided me data and case study information including R. David Pyne, Paul Pavelic, Dr.
June Mirecki, lan Gale, Mark McNeal, Kevin Mooris, Susan Mulligan, Don Kendall,
Everitt Wegerif, Rick Nipper, John Zimmerman, Randy Beavers, Ted Corrigan, Paul
Eckley, Dave Winship, Billy Smith, Bob Schwartz, Rick Lahy, Dr. Mark Pearce, Larry
Eaton, Dr. Jon Arthur, Paul Stanfield, Dr. Mary Anderson, Doug Geller, Joel Hall, Mike
Zygnerski, Dr. Tom Missimer, Dr. Christian Langevin, and Dr. Pearce Cheng. I
acknowledge a special thanks to my University of Florida advisors including Dr. Kirk
Hatfield, Dr. Louis Motz, Dr. Mark Brenner, Dr. William Wise, and Dr. Jon Martin. Drs.
Hatfield and Motz especially deserve singular thanks for the hours of time spent with me
helping improve my research and publishing the results.
TABLE OF CONTENTS
ACKNOWLEDGMENT S ............. .................... iv
LIST OF TABLES ................. ..............ix. .......... ....
LI ST OF FIGURE S .............. .................... xii
AB S TRAC T ......_ ................. ..........._..._ xviii..
1 INTRODUCTION .............. ...............1.....
Description of Artificial Recharge. ..........._.... ..........._........... ............. .....1
Description of Aquifer, Storage and Recovery (ASR) ................ ................. ...._6
Advantages and Disadvantages of ASR ........._.___..... .__. ......._..........9
Regulation of ASR. ........._.___..... .__. ...............12....
ASR Use and Constraints .............. ...............19....
Potable Use .........._.... .. ....._ __ ...............25.....
Agricultural and Irrigation Use .............. ...............26....
In-stream and Environmental Use ....._.__._ ..... ... .__. ......._...........2
2 ASR PLANNING MEANS AND METHODS .............. ...............29....
Current Planning Methodology of ASR Proj ects ................. ......... ................29
Planning at Non-brackish Water ASR Sites ................. .......... ................3 7
Planning at Brackish Water ASR Sites .............. ...............37....
Formulation of an Improved Planning Methodology .............. ....................3
Review of ASR Performance Factors. ................ ................. ..............39
General discussion of all ASR sites .............. ...............40....
Brackish water ASR sites ................. .......... ............... 53. ....
Review of Other ASR Site Selection Factors ................. .......... ...............67
Collection of Existing ASR Site Data ................. ...............67...............
Non-brackish water ASR sites .............. ...............69....
Brackish water ASR sites ................. ...............114...............
Comparison of Existing ASR Site Data ................. ............... ......... ...159
Non-brackish water ASR sites .............. ...............160....
Brackish water ASR sites .......................... .......... .............6
Development of ASR simulator models ................. .........................170
Confirmation of ASR performance factors ............_.. .....__ ...........179
3 RESULTS AND DISCUSSION NEW ASR PLANNING DECISION
FRAMEWORK .............. ...............195....
Development of ASR Performance Guidelines and Metrics ................ ... .................195
General Guidelines for all ASR Sites with Consideration of ASR Use for
Potable, Irrigation or In-stream purposes ................. .......... ...............196
Hy drogeol ogy ....__. ................. ........_.._.........19
Hydraulic ...._. ................. ...............199......
Geotechnical ................. ...............205......... ......
W ater quality ................. ...............213......... ......
Environmental impacts............... .... ... ...........23
Legal, institutional and social considerations .............. ....................23
Engineering .............. .. ............... .... ...............24
Special Considerations Specific for Brackish Water ASR Sites ................... ....251
Thickness of storage zone .............. ........ ..............25
Effect of aquifer regional pre-existing gradient ................. ......._.........252
Recharge volume .....___................. ........___ .......... 25
Dispersivity .............. ...............254....
ASR storage duration .............. ...............260..
Density of ambient groundwater in storage zone ................. ................. .261
Recharge and ambient groundwater water quality ............... ................. 262
Effect of multiple consecutive cycles. .....__.___ ..... .._. ................ .264
Aquifer homogeneity/isotropy .............. ...............265....
Dipping storage zones .............. ...............266....
Aquifer transmissivity .............. ...............266....
Aquifer porosity ................... ...............267.
Brackish Water Performance Metrics .............. ...............268....
Dimensionless recovery index .............. ...............269....
Dimensionless relative dispersivity ................. ............... ......... ...272
Compilation of model simulations .............. ...............274....
ASR brackish water performance envelopes .............. .....................7
Cumulative recovery efficiency as a metric ................. ............ .........285
Validation of new ASR performance metrics .............. ....................28
Proposed New Planning Decision Framework ....._____ .........__ ...............293
ASR Suitability Index................. ... ..............29
Planning Decision Framework Procedure ....._____ ..... ... __ ................. 297
Testing of Planning Framework at Two ASR Sites. ................ ................. .....307
Overview of Two ASR Validation Sites .............. ...............307....
Lake Okeechobee, Florida, site ................ ...............307.....__ ....
Kerryille, Texas, site ................. .... ... ........... ..........30
Testing of Planning Framework at the Two Validation Sites ................... ........31 1
Framework validation at Lake Okeechobee, Florida, site ................... .......311
Framework validation at Kerryille, Texas, site ................ ............... ....320
Amendments to Proposed Planning Decision Framework ................... ... ................ 323
Application of New Planning Decision Framework at CERP ASR Pilot Sites........324
4 CONCLUSIONS AND RECOMMENDATIONS FOR FURTHER RESEARCH .351
A LIST OF PUBLICATIONS DERIVED FROM DISSERTATION.........................359
B PARTIAL COMPILATION OF ASR MODEL RESULTS .............. ........._.....36 1
LIST OF REFERENCES .........__._..... ..__. ...............367...
BIOGRAPHICAL SKETCH .............. ...............395....
LIST OF TABLES
1-1. Distribution of 89% of AR wells in the United States .............. .....................
1-2. Primary constraints for different ASR uses ................. ...............20........... .
2-1. Data from Cocoa Beach ASR field trial .............. ...............57....
2-2. Data from Hialeah ASR field trial .................._.__._ ......... ..........13
2-3. Data from initial cycle testing at Peace River ASR site ................. ........._._. ....141
2-4. Summary hydrogeologic data for 14 Florida brackish water ASR sites (NA
means data not available) ................. ......... ...............145 ....
2-5. Summary hydrogeologic data for five international brackish water ASR sites (NA
means data not available) ................. ......... ...............153 ....
3-1. Recommended TSS limits from ASCE .............. ...............214....
3-2. Recommended TSS and TOC guidelines for ASR projects derived from this
research report ................. ...............215................
3-3. Recommended TDS guidelines for ASR projects. All values listed in mg/1..........215
3-4. Recommended Chloride guidelines for ASR projects. All values listed in mg/1...216
3-5. Recommended Sodium guidelines for ASR proj ects. All values listed in mg/1.....216
3-6. Recommended Sulfate guidelines for ASR projects. All values listed in mg/1......217
3-7. Regulatory limits for disinfection by-products and disinfectants themselves........ .224
3-8. Required percentage removal of TOC .....__................. .........___......22
3-9. Regulatory Guidance Values from the State of Florida, EPA, Canada, and
Australia/New Zealand. All concentrations listed in ug/1 except radium..........._...228
3-10. Regulatory Guidance Values from the State of Florida, EPA, Canada, and
Australia/New Zealand for select pesticides, herbicides, and microcystin. All
concentrations listed in ug/1 ................. ...._ _. ...._.._ .. .... .....23
3-11. Research results relating ASR recovery effciency versus aquifer storage zone
thickness (b) .............. ...............252....
3-12. Research results relating ASR recovery effciency versus pre-existing aquifer
gradient (i) ................. ...............253...............
3-13. Research results relating ASR recovery effciency versus recharge volume ........253
3-14. Research results relating ASR recovery effciency versus dispersivity ................254
3-15. General unconsolidated aquifer character versus degree of dispersion expected
during ASR recharge and recovery .............. ...............256....
3-16. General rock aquifer character versus degree of dispersion expected during ASR
recharge and recovery .............. ...............256....
3-17. General aquifer character versus estimated dispersivity .............. ....................25
3-18. General unconsolidated aquifer character versus dispersivity range expected
during ASR recharge and recovery .............. ...............259....
3-19. General rock aquifer character versus dispersivity range expected during ASR
recharge and recovery .............. ...............259....
3-20. Research results relating ASR recovery effciency versus storage duration........ .260
3-21. Research results relating ASR recovery effciency versus density differential.....261
3-22. Research results relating ASR recovery effciency versus ambient groundwater
quality ........._...... ...............263...__..........
3-23. Research results relating ASR recovery effciency versus number of recharge
and recovery cycles .............. ...............264....
3-24. Research results relating ASR recovery effciency versus degree of aquifer
homogeneity ........._.._.. ...._... ...............265....
3-25. Research results relating ASR recovery effciency versus degree of aquifer
isotropy ........... __..... ._ ...............266....
3-26. Research results relating ASR recovery effciency versus aquifer transmissivity 267
3-27. Research results relating ASR recovery effciency versus aquifer porosity .........268
3-28. ASR Sites with estimated dispersivity values .............. ...............288....
3-29. Real site estimates of dispersivity versus linear regression model estimates ........289
3-30. Recommended power law coeffieients and exponents for estimating dispersivity
3-31. Recommended power law coeffieients and exponents for estimating dispersivity
values including new medium categories developed for this research report........293
3-33. Taylor Creek ASR alternatives 1, 2, and 3 with predicted RE percentage. ...........317
3-34. CERP ASR Pilot Projects key supporting technical data. .................. ...............330
3 -3 5. ASR Pilot Proj ects with predicted RE percentage ........._..... ......__.. ...........3 44
LIST OF FIGURES
1-1. A typical ASR well (courtesy of CH2M Hill, Inc.) .............. ..... ............... 8
2-1. The effect of storage period on recovery efficiency ................. ................. ...._45
2-2. The effect of inj section volume in million gallons on recovery efficiency ................46
2-3. Results from historical reports by Merritt et al. (1983) and Merritt (1986) The y-
axis is RE percentage and the x-axis is ASR cycle number .................. ...............62
2-4. Location of ASR proj ect sites where data were collected for this report .................. .68
2-5. Location of non-brackish water ASR proj ect sites where data were collected for
this report............... ...............70.
2-6. ASR recovery curve for cycle 1 at Myrtle Beach, South Carolina. ................... .......108
2-7. General hydrogeological cross-section of the Lytchett Minster site in England
(used with permission from Paul Stanfield, Wessex Water) ................. ...............111
2-8. Cycle testing results compared to other published data from Pyne (1995) (used
with permission from Paul Stanfield, Wessex Water) ................. ............... .....112
2-9. Location of brackish water ASR proj ect sites where data were collected for this
report ................. ...............114......... ......
2-10. Boynton Beach cycle 1 recharge and recovery cycle chloride water quality
versus elapsed time in days .............. ...............124....
2-11. Boynton Beach long-term cumulative recovery efficiency versus ASR cycle
number along with trend line for same............... ...............125.
2-12. Palm Bay long-term cumulative recovery efficiency versus ASR cycle number
along with trend line for same ................. ...............131..............
2-13. Hialeah cycle 1 through 3 recharge and recovery cycles, chloride water quality
versus elapsed time in days .............. ...............134....
2-14. Tampa Rome Avenue Park ASR generalized site hydrogeology and location of
selected ASR storage zone (elevations are feet below land surface; figure used
with permission of Mark McNeal, CH2M Hill) .......... ................ ...............136
2-15. Tampa Rome Avenue Park ASR generalized brackish water upcoming (deep
aquifers within the FAS contain much higher TDS; figure used with permission
of Mark McNeal, CH2M Hill) ................. ...............138........... ...
2-16. Cycle 2 recovery arsenic data for Peace River well # S11 ................ ................. 143
2-17. Cycle 1 recovery data for Delray Beach ASR well ................ .......................147
2-18. Cycle 2 recovery data for Lee County North ASR well ..........._. .... .............. ..148
2-19. Cycle 1 recovery data for Lee County Olga ASR well .............. ....................14
2-20. Cycle 1 recovery data for Broward County WTP ASR well ................. ...............150
2-21. Cycle 3 recovery data for Fiveash ASR well ................. ............................15
2-22. Cycle 1 recovery data for Fort Myers Winkler Avenue ASR well ........................151
2-23. Cumulative Recovery Efficiency (CRE) versus cycle number for eight brackish
water Florida ASR sites............... ...............152.
2-24. Model domain for ASR model simulator A, the domain is 40 miles....................173
2-25. Comparison of model predictions with numerical and analytical models .............174
2-26. Comparison of ASR simulator models and alternate transport solutions.. .............176
2-27. Comparison of ASR Simulator B results using two alternate transport solutions..177
2-28. Comparison of ASR Simulator A and B results using same model run conditions
with ambient groundwater TDS concentration equal to 4,000 mg/1 ......................178
2-29. Comparison of ASR simulator C predicted RE% results using same model run
conditions with AWQ equal to 1,000 mg/1 and RWQ equal to 5 mg/1, but
changing the storage zone thickness .............. ...............181....
2-30. Comparison of ASR simulator C predicted RE% results using same model run
conditions with AWQ equal to 1,000 mg/1 and RWQ equal to 5 mg/1, but
changing the regional pre-existing groundwater gradient ................. ................. 182
2-31i. Comparison of ASR simulator C predicted RE% results using same model run
conditions with AWQ equal to 1,000 mg/1 and RWQ equal to 5 mg/1, but
changing the recharge volume ................. ...............183...............
2-32. Comparison of ASR simulator C predicted RE% results using same model run
conditions with AWQ equal to 1,000 mg/1 and RWQ equal to 5 mg/1, but
changing the dispersivity ................. ...............184................
2-33. Comparison of ASR simulator C predicted RE% results using same model run
conditions with AWQ equal to 1,000 mg/1 and RWQ equal to 5 mg/1, showing
best-fit logarithmic curve .............. ...............185....
2-34. Comparison of ASR simulator B predicted RE% results using same model run
conditions with ambient groundwater TDS equal to 4,000 mg/1 and recharge
TDS equal to 150 mg/1, dispersivity is assigned zero foot............... .................18
2-3 5. Comparison of ASR simulator B predicted RE% results using ambient
groundwater TDS equal to 35,000 mg/1 and recharge TDS equal to 150 mg/1,
dispersivity is assigned zero foot .............. ...............188....
2-36. Comparison of ASR simulator C predicted RE% results using ambient
groundwater chloride equal to 1,000 mg/1 and recharge chloride equal to 5 mg/1,
dispersivity is assigned as shown ................. ...............189........... ...
2-37. Comparison of ASR simulator C predicted RE% results using ambient
groundwater chloride equal to 2,000 mg/1 and recharge chloride equal to 5 mg/1,
dispersivity is assigned as shown ................. ...............190........... ...
2-3 8. Comparison of ASR simulator C predicted RE% results using ambient
groundwater chloride equal to 3,000 mg/1 and recharge chloride equal to 5 mg/1,
dispersivity is assigned as shown ................. ...............191........... ...
2-39. Comparison of ASR simulator C predicted CRE% results using ambient
groundwater chloride equal to 2,000 mg/1 and recharge chloride equal to 5 mg/1,
dispersivity is assigned as shown ................. ...............192........... ...
2-40. Comparison of ASR simulator C predicted CRE% results using ambient
groundwater chloride equal to 2,000 mg/1 and recharge chloride equal to 5 mg/1,
dispersivity is assigned as shown, with logarithm best-fit curves shown .............. 193
2-41. Comparison of ASR Simulator C predicted RE% results using ambient
groundwater chloride equal to 2,000 mg/1 and recharge chloride equal to 5 mg/1,
dispersivity is assigned as shown, using both homogeneous and heterogeneous
transmissivity distributions .............. ...............194....
3-1. Unconfined aquifer ASR planning guideline for water storage volume versus
recommended storage zone radius at various aquifer thicknesses (b) ...................197
3-2. Confined aquifer ASR planning guideline at various aquifer transmissivities with
recharge rate equal to 1 MGD for 50 days ................ ...............200............
3-3. Confined aquifer ASR planning guideline at various aquifer transmissivities with
recharge rate equal to 2.5 MGD for 50 days ................ ................ ......... .201
3-4. Confined aquifer ASR planning guideline at various aquifer transmissivities with
recharge rate equal to 5 MGD for 50 days ................ ...............201............
3-5. ASR performance for operational strategy # 1. RE is recovery efficiency, CRE is
the cumulative recovery efficiency, and alpha is the dispersivity ................... .......248
3-6. Recovery Index (RI) versus Cycle one recovery efficiency (RE%) for brackish
water ASR sites where recharge rate was greater than 0.5 MGD and less than 3
M GD ........._ ....... __ ...............271...
3-7. Recovery Index (RI) versus Cycle one recovery efficiency (RE%) for brackish
water ASR sites where recharge rate was less than 0.5 MGD ............... ...............271
3-8. Time versus chloride concentration for select ASR sites discussed in this report. .276
3-9. Time versus chloride concentration for select ASR sites discussed in this report
and model simulation results ................. ...............276...............
3-10. Multiple linear regression model # 1 results compared to original numerical
model predictions of RE percentage. ............. ...............278....
3-11. Multiple linear regression model # 5 results compared to original numerical
model predictions of RE percentage. ............. ...............278....
3-12. ASR RE percentage as a function of inverse relative dispersivity (R,') and
recovery index (RI). A "family" of RI graphs is shown to facilitate use............_..280
3-13. ASR RE percentage as a function of inverse relative dispersivity (R,') and
recovery index (RI) for AWQ equal to 500 mg/1..................... ............... 28
3-14. ASR RE percentage as a function of inverse relative dispersivity (R,') and
recovery index (RI) for AWQ equal to 1,000 mg/1..................... ...............28
3-15. ASR RE percentage as a function of inverse relative dispersivity (R,') and
recovery index (RI) for AWQ equal to 1,500 mg/1..................... ...............28
3-16. ASR RE percentage as a function of inverse relative dispersivity (R,') and
recovery index (RI) for AWQ equal to 2,000 mg/1..................... ...............28
3-17. ASR RE percentage as a function of inverse relative dispersivity (R,') and
recovery index (RI) for AWQ equal to 2,500 mg/1..................... ...............28
3-18. ASR CRE percentage versus # of recharge and recovery cycles for AWQ equal
to 1,000 m g/1. ............. ...............286....
3-19. ASR CRE percentage versus # of recharge and recovery cycles for AWQ equal
to 2,000 m g/1 .............. ...............286....
3-20. Real site dispersivity estimates versus linear regression model estimates. Also
shown is the resulting straight line if the model was perfect. ............. ..... .........._.288
3-21. Real site RE estimates versus linear regression model RE estimates. Also
shown is the resulting r2 coefficient. ............. ...............291....
3-22. Real site RE estimates versus linear regression model RE estimates using Power
Law equations to estimate dispersivity. Also shown is the resulting r2
coefficient ................. ...............294................
3-23. Proposed ASR Planning Decision Framework in generalized form. ................... .300
3-24. Proposed ASR Planning Decision Framework Step # 2 with key details of
evaluations required. ............. ...............301....
3-25. Proposed ASR Planning Decision Framework Step # 3 with key details of
evaluations required. ............. ...............302....
3-26. Proposed ASR Planning Decision Framework Step # 4 with key details of
evaluations required. ............. ...............303....
3-27. Proposed ASR Planning Decision Framework Steps # 5 and 6 with key details
of evaluations required. .............. ...............3 04...
3-28. Proposed ASR Planning Decision Framework Steps # 7 to 10 with key details
of evaluations required. .............. ...............3 06...
3-29. Predicted head increase from recharge rate of 5 MGD at the Lake Okeechobee
Taylor Creek ASR site. ............. ...............315....
3-30. RE estimate for the Taylor Creek ASR site using graphical method. ...................318
3-31. CRE estimate for the Taylor Creek ASR site using graphical method. ..............319
3-32. Expected head increase from Kerryille alternative 1............... ....................2
3-33. Location and capacity of proposed CERP ASR Wells in southern Florida. ..........326
3-34. General location of the CERP ASR Pilot Proj ects. ................ .......................327
3-3 5. Location and general hydrogeology at the Hillsboro ASR pilot proj ect. ...............329
3-36. Location and general hydrogeology at the Hillsboro ASR pilot proj ect. ...............333
3 -3 7. Location of the Port Mayaca ASR pilot site ................. ............... 334...........
3-3 8. Location of the Kissimmee River ASR pilot site. ................ ................ ...._.33 5
3-39. Location of the Moore Haven ASR pilot site ................. ................ ........ .337
3-40. Location of the Caloosahatchee River ASR pilot site. ................ ............... .....33 8
3-41. Estimated head changes within Upper Floridan Aquifer System at the ASR Pilot
Proj ects ................. ...............342................
3-42. RE estimates for Kissimmee River and Caloosahatchee River ASR Pilot
Proj ects. ................. ...............3.. 45.............
3 -43. RE estimate for Port Mayaca ASR Pilot Proj ect ................. ........................345
3-44. RE estimates for Hillsboro Canal and Moore Haven ASR Pilot Proj ects. ............346
3-45. CRE estimates for Kissimmee River, Caloosahatchee River, and Port Mayaca
ASR Pilot Proj ects ................. ...............347...............
3-46. CRE estimates for Hillsboro Canal and Moore Haven ASR Pilot Projects. .........348
B-1. Partial compilation of model results. ............. ...............366....
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
PLANNING DECISION FRAMEWORK FOR BRACKISH WATER AQUIFER,
STORAGE AND RECOVERY (ASR) PROJECTS
Christopher J. Brown
Chair: Kirk Hatfield
Cochair: Louis H. Motz
Major Department: Civil and Coastal Engineering
Aquifer Storage and Recovery (ASR) proj ects are being utilized for an ever-
increasing number of water management proj ects nationwide. A large number of ASR
proj ects are in operation in the United States with many others in the early planning
stages. The planning of ASR proj ects involves consideration of numerous qualitative and
quantitative factors including site location, applicable regulations, availability of water,
type and quantity of water demands, source water quality, subsurface hydrogeology,
ambient groundwater quality, geochemistry, geotechnical constraints, and many others.
Currently, the planning of potential ASR proj ects is not standardized. Often, feasibility
of ASR is based upon an incomplete consideration of important planning factors. ASR
practitioners would be provided a great benefit if a formalized ASR planning decision
framework could be developed. This is especially true for ASR sites located within
brackish groundwater environments. For these sites, a formalized framework is lacking
that includes reliable planning metrics designed to permit a quick assessment of proj ect
The primary purpose of this research proj ect was the development of a formalized
planning decision framework for new brackish water ASR proj ects. The framework
consists of planning procedures, qualitative guidance, quantitative guidance, and new
ASR performance metrics. The framework is designed to aid the ASR community of
practice in assessing the feasibility of prospective proj ects. The framework, guidance
values, and new metrics are based upon a compilation of literature, summaries of 50
different ASR proj ects from around the world, and extensive numerical modeling of ASR
performance. The framework, guidance values, and performance metrics were validated
at two ASR proj ect sites not included in the initial data compilation and then was applied
to five proposed ASR proj ects under consideration as part of the Comprehensive
Everglades Restoration Plan (CERP).
Description of Artificial Recharge
The concept of underground storage of water has been around for millennia.
Nomads in the Middle East have long recognized that sand dunes are a dependable source
of recharge after rain events. The nomads of Turkmenistan capitalized on this knowledge
by digging long trenches extending radially from various sand dune systems (Pyne,
1995). The Romans utilized cisterns for water storage for generations. The modern term
"artificial recharge" has been recognized only recently through efforts of notable
engineers and scientists such as Cederstrom, Harpaz, and Bear. Their efforts, and those
of many others, have provided the theoretical basis and practical experience to
successfully implement artificial recharge proj ects.
Recharge to groundwater aquifers is ultimately derived from rainfall that falls on
the land. Much of the rainfall that occurs on the land runs off to nearby surface water
bodies, evaporates, or is abstracted for various water supply uses. Only a fraction of the
total rainfall reaches subsurface aquifers via percolation into the ground. Recharge to a
surficial water-table (unconfined) aquifer is generally higher than comparable recharge
amounts to deeper, confined, aquifers due to proximity to the land surface. According to
the American Society of Civil Engineers (ASCE), recharge is
the replenishment of ground water by downward infiltration of water from rainfall,
streams, surface depressions, and other sources, or by introduction of water directly
into an aquifer through wells, galleries, or other means. Recharge can be either
natural or artificial. (ASCE, 2001, p. 3)
Modern artificial recharge (AR) is the process of augmenting natural recharge of
groundwater aquifers. According to the National Research Council (NRC), AR is:
a process by which excess surface water is directed into the ground either by
spreading on the surface, by using recharge wells, or by altering natural conditions
to increase infiltration to replenish an aquifer. (NRC, 1994, p. 1)
AR provides a means to store water underground in times of water surplus to meet
demand in times of shortage. Water recovered from AR proj ects can be utilized for a
variety of potable and non-potable uses. AR can also be used to control seawater
intrusion in coastal aquifers, control land subsidence caused by declining ground water
levels, maintain base flow in some streams, and raise water levels to reduce the cost of
groundwater pumping (NRC, 1994).
Recharge can be introduced through various surface infiltration methods or
through wells. Recharge can be introduced into the saturated or unsaturated portions of
an aquifer. Both unconfined and confined aquifers have been used for AR (ASCE,
2001). Surface spreading methods are mainly amenable in unconfined aquifers (Asano,
1985), while wells are utilized to recharge confined aquifers (NRC, 1994).
Surface spreading methods introduce water at the land surface into unconfined
aquifers. The percolated water passes through permeable geologic materials and enters
into the water table aquifer. In arid regions, a substantial unsaturated zone exists to
accommodate surface recharge operations. Usually, a groundwater mound forms beneath
the surface spreading basin as infiltrated water reaches the water table aquifer (Abe,
1986). According to Asano (1985), long-term losses from surface spreading are
predominantly due to evapo-transpiration. Technical factors affecting feasibility of such
an approach include infiltration rates, depth to water table, degree of hydrologic
continuity between surface and water table (Wilson, 1979). Sediment and biological
clogging, shallow perched zones controlled by geology, air entrainment, and temperature
differences between groundwater and recharge water, and salinity of recharge water
control infiltration rates. Surface systems must be tailored to local hydrogeology, quality
of input water, and climate (NRC, 1994). Surface spreading can be accomplished
through recharge basins, in-channel recharge zones, off-channel recharge zones, leach
mounds, and other techniques. Surface spreading techniques are generally easier to
develop as compared to recharge wells and both approaches have advantages and
disadvantages. According to Abe (1986), advantages of surface spreading include:
* Construction costs are generally much lower for spreading facilities than recharge
* Operation and maintenance costs are generally lower and little to no water
treatment is required prior to recharge.
* Large volumes of water may be recharged rapidly.
* Channel modification takes advantage of natural hydrologic connections with
* Recharge near streams may provide for environmental enhancement.
According to Abe (1986), disadvantages of surface spreading include:
* Evaporation losses may be higher than for recharge wells
* Time lag between recharge and recovery may be substantial.
* Land availability or costs may be substantial
* Floods or animals (turtles, rodents, etc.) may cause severe damage to containment
* Surface recharge basins can become an attractive nuisance (e.g., attracting
mosquitoes or potential for drowning).
* Periodic scraping may be required in the surface recharge basins to restore full
Thick unsaturated zones may be problematic unless a complete subsurface
characterization has been completed due to possibility of controlling geological features.
These features may lead to a circuitous flow path that may cause excessive time to elapse
before recharge water reaches the water table.
If surface spreading methods are infeasible for conducting AR proj ects, wells may
be employed for this purpose. Recharge wells are similar to regular pumping wells. In
unconsolidated aquifers consisting of sands, gravels or silts, the wells consist of a well
casing, well screen, well filter pack, and an injection pipe. In bedrock aquifers, the
recharge well may have an open-hole interval rather than a well screen. Recharge wells
located in confined aquifers may have several small diameter recharge pipes terminated
in different aquifer zones. Most recharge wells are connected to pumps that allow
recharge to occur at high rates. Beyond their increased costs, the maj or problem with
inj section wells is clogging of the aquifer around the well, especially at the borehole
interface between the filter pack and aquifer where suspended solids can accumulate
Asano (1985) argues that in order to maintain high intake rates for recharge wells,
operation and maintenance of the well system must include water treatment prior to
recharge and periodic well redevelopment. Sternau (1967) and Wilson (1979)
recommend dual-purpose well systems to save the cost of well construction and
conveyance systems. They also offer two advantages: namely, installed pumps may be
used for well redevelopment and to recover stored water. To maximize recharge and
pumping efficiency, the bottom of the recharge conduits should remain submerged. This
also eliminates the problem of air entrainment in the case of water cascading down the
well casing. According to Abe (1986), advantages of recharge wells are:
* Recharge wells introduce water directly into the water table or aquifer with
* Recharge by wells may be the only suitable means for recharge due to geology or
* Water recharged by wells can be recovered quickly and efficiently. Slow
groundwater movement allows recovery out of the same well usually.
* Recharge wells may reduce conveyance costs.
According to Abe (1986), disadvantages of recharge wells are:
* High construction costs including well and treatment plant construction.
* O&M costs are high primarily due to water treatment prior to recharge.
* In highly permeable aquifers, maintaining a positive outward head is expensive and
requires large volumes of water.
* Capacity is much smaller than surface-spreading facilities.
A recent EPA study reviewed 23 categories of Class V inj section wells in the United
States (EPA, 1999a). EPA estimates that there are 686,000 Class V wells in the USA.
The two largest categories are storm water drainage wells (248,000) and large-capacity
septic systems (3 53,000) that together comprise almost 88% of the totals. The EPA also
noted that a few categories like subsidence control wells have less than 100 recorded total
wells. Class V wells exist in virtually every state in the USA. Salt-water and subsidence
control wells exist in only six or fewer states. The study identified 315 salt-water
intrusion barrier wells and 1,185 AR wells out of total Class V wells surveyed.
In a continuation of the Class V inj section well study, the United States
Environmental Protection Agency (EPA) inventoried 1,185 AR wells within the United
States (EPA, 1999b). Approximately 89% of the AR wells are located in 11 states
including California, Colorado, Texas, Florida, Idaho, Nevada, Oklahoma, Oregon, South
Carolina, Washington, and Wisconsin. Table 1 provides the well distribution for these
Table 1-1. Distribution of 89% of AR wells in the United States
State Number of AR wells
Florida +/- 488*
South Carolina 55
Some of the wells may be lake control wells. Source (EPA, 1996b)
AR proj ects have been tested and successfully utilized by a number of United States
government agencies including the Bureau of Reclamation (1996a, 1998), United States
Geological Survey (Vecchioli and Ku, 1972; Fitzpatrick, 1986; Buszka et al., 1994), and
United States Army Corps of Engineers (Wilson, 1979), in a variety of environments.
AR is increasingly utilized by the private sector worldwide to help provide dependable
water supply (ASCE, 2001). Outside the United States, AR has been used extensively.
Fifteen percent of Germany's water supply needs are provided via AR (Schottler, 1996).
In Israel, borehole injection into a dolomitic aquifer has recharged on average 1.1 million
cubic meters per year over a 23-year period (Guttman, 1995). South Africa has utilized
AR to replenish aquifers for decades (Murray, 2004).
Description of Aquifer, Storage and Recovery (ASR)
ASR is a simple concept in which water is stored in subsurface permeable aquifers
when water is plentiful and extracted during times of peak demand. According to the
British Geological Survey (Jones et al. 1999, p. 3), ASR is a sub-set of artificial recharge
and is defined as:
storage of treated, potable water in the aquifer local to the borehole(s) that is (are)
used for both inj section and abstraction. A high percentage of the water inj ected is
abstracted at a later date and the scheme may utilize an aquifer containing poor
quality or brackish water, although this does not exclude the use of aquifers
containing potable water. ASR schemes enable maximum use to be made of
existing licensed resources.
Pyne (1995, p. 6) has defined ASR as
the storage of water in a suitable aquifer through a well during times when water is
available, and recovery of the water from the same well during times when it is
Artificial recharge of groundwater through wells has been explored in diverse
settings internationally (Cederstrom 1957; Harpaz 1971; Bichara 1974; Meyer 1989;
Bouwer et al., 1990; Johnson and Pyne, 1995; Kendall 1997; Merritt 1997, Peters 1998,
Dillon 2002). Groundwater recharge has been utilized in South Florida, New Jersey and
California for decades to reverse the effects of salt-water intrusion. ASR wells extend
this traditional recharge process by providing the opportunity for subsequent recovery of
the water at the same location. ASR wells are a combination of recharge and recovery
wells and are commonly designed for seasonal, long-term, or emergency storage (ASCE,
An ASR site consists of one or more recharge wells, monitoring wells as required, a
treatment facility, and a receiving basin or structure for recovered water storage. Figure 1
depicts a typical ASR site. An ASR well is typically a larger diameter production well
Figure 1-1. A typical ASR well (courtesy of CH2M Hill, Inc.)
with a large wellhead. ASR wells are typically cased down to the depth of the permeable
zone used for storage. Monitoring wells are required by permit at most production sites;
these wells enable tracking of recharged water during ASR operation. A typical
monitoring well is installed 50 to 1,000 feet from the ASR recharge well and has a screen
or open-hole interval at a depth equal to the recharge well. In Florida, regulators may
also require construction of shallow surficial monitoring wells to detect changes in
potentiometric head or discover upward leakage resulting in observable water quality
deviations. Treatment requirements vary from site to site with some municipal water
utilities using existing treatment capacity during low demand intervals while other ASR
users utilize in-line treatment operations on a more regular basis.
The use of ASR is proliferating throughout Florida and internationally with sites in
operation or development in the United States, Canada, England, Australia, Israel, South
Africa, Tanzania, Netherlands, and Kuwait (Jones et al. 1999). The EPA documented
approximately 130 ASR wells within the United States (EPA, 1999b).
ASR technology has been adopted as a groundwater management strategy in many
diverse hydrogeologic settings. For example, ASR is utilized in South Florida (confined
carbonate aquifer), Virginia and New Jersey (confined plastic aquifers), and Washington
(confined fractured-igneous aquifer) for a variety of purposes including urban and
agricultural water supply (Brown & Silvey, 1977; Pyne 1995; Reese 2002; Bureau of
Reclamation, 1994). However, most ASR systems in the United States are dedicated to
recharge and recovery of water that meets potable water quality standards (Pyne, 1995).
A few of the systems are very large including the system utilized by the Las Vegas
Valley Water District (LVVWD) which consists of 52 wells recharging up to 80 million
gallons per day (MGD), (AWWARF, 2003). Increasingly, ASR is conducted using
reclaimed storm-water, for subsequent recovery for irrigation purposes (McNeal et al.
1997; Barnett 2000; Gerges et al. 2002). The use of ASR to meet in-stream
environmental demands is a relatively new application but one that will be considered in
many future projects (USACE, 1999; AWWA, 2002).
Advantages and Disadvantages of ASR
ASR has been recognized as an innovative option for water supply and is being
considered in many new proj ects around the world (Butts, 2002; Durham et al., 2002).
ASR has advantages and disadvantages compared to surface storage options (Smith et al.,
2000). ASR systems generally require less land acreage, which is particularly suited for
urban systems where surface storage is infeasible. ASR systems can reduce water losses
due to seepage and evapo-transpiration, which is a key consideration in arid
environments. ASR wells can be located in the areas of greatest need, thus reducing
water distribution costs, and augmenting surface water supplies (USACE, 1999).
Kasman (1967) noted that using aquifers as cyclic storage reservoirs provided a
number of advantages including:
* Lack of permanence
* No loss of storage capacity due to sedimentation
* No loss of water due to evaporation
* Less vulnerability to destruction and contamination
* Absence of downstream threats due to dam failure
Many advantages of ASR wells have been proposed including the following (Pyne 1995):
* Seasonal water storage to meet peak demands
* Long-term storage to meet drought demands
* Emergency source of potable water
* Disinfection by-products reduction
* Restoring natural groundwater levels
* Reducing subsidence
* Improve water quality
* Preventing salt-water intrusion
* Agricultural water supply
* Storage of reclaimed water
Undoubtedly, other applications will be developed also. Many professionals see
aquifer recharge as an opportunity to expand water supplies in the future (Bureau of
Reclamation, 1994; Stussman, 1997; Durham et al. 2002). Many upcoming applications
may not be related to human needs, but they may be developed for in-stream
environmental benefits or environmental restoration purposes (AWWA, 2002).
ASR systems can also have significant disadvantages in some cases. Examples of
potential disadvantages include low recharge and recovery efficiencies relative to surface
storage, which limit capture rates of excess water. Water quality changes that result from
mixing with brackish or saline aquifer groundwater may limit the subsequent recovery of
stored water (USACE and SFWMD, 1999). Recharge of fresh water into saline aquifers
may result in significant buoyancy stratification where fresh water moves upward and out
of the permeable injection zone due to density differences (Merritt, 1986; Missimer et al.
While slightly brackish water may be acceptable for irrigation (less than 1,500
mg/L total dissolved solids) or drinking water (less than 500 mg/L total dissolved solids)
purposes, increased salinity, and other water quality changes that result from discharge of
ASR water to surface ecosystems, may have unknown ecological effects (NRC, 2002).
Detrimental geochemical reactions between the aquifer matrix and the recharged water
can increase post-recovery treatment costs, thus rendering a potential proj ect
uneconomical (Arthur et al. 2002; Gaus, 2002). Operations and maintenance costs may
also be higher for ASR, largely due to high-energy requirements related to pumping or
water treatment systems (NRC, 2002a). In some projects, issues involving subsidence
can reduce the storage zone permeability or geotechnical integrity of the ASR system (Li
and Helm, 2001; Brown et al. 2004). ASR wells can also become clogged due to a
combination of biological, chemical, and physical processes (Rinck-Pfeiffer et al. 2000).
Well clogging may constitute an ongoing maintenance problem, particularly in ASR
systems that manage treated wastewater or raw storm-water.
Regulation of ASR
With the advent of larger ASR well field proj ects around the world, the regulatory
limitations and constraints they present loom large. ASCE noted that legal and regulatory
requirements are an important part of any AR proj ect (ASCE, 2001). ASCE
recommended the following legal considerations be considered for any proj ect:
* Ability to maintain control of recharged water
* Surface water and ground water storage rights
* Permits and decrees
* Controls on use of reclaimed water
* Liabilities associated with water quality issues
* Type of ownership
* Land ownership
* Site assessments
In the United States, ASR technology often proceeds in advance of regulatory
guidelines, so that permit requirements vary from state to state and within a state over
time. ASR planners must lobby regulators to develop a more integrated ASR regulatory
framework. The regulatory framework provides ASR planners the constraints that
potential ASR projects need to work within. In many cases, the existing regulatory
framework controls the ultimate feasibility of a promising ASR application. The
American Water Works Association (AWWA, 2002) surveyed 46 separate ASR proj ects
in the United States and discussed the overall complexity of the regulatory issues
involved in the development and operation of ASR systems. Not surprisingly, the report
clearly demonstrates the regulatory inconsistencies within states and across the United
States. The twisted maze of regulations relating to ASR technology may be slowing
technological innovation due to perceived risks of ASR implementation.
The development of a new planning decision framework for brackish water ASR
projects must include regulatory and legal considerations in its development. A
standardized planning decision framework would also enable regulators to "ask the right
questions" when evaluating proposed new ASR proj ects. The use of ASR technology in
the United States would benefit from a more holistic regulatory approach that is
consistent and based upon a common planning framework. A more consistent regulatory
approach to ASR proj ects across the United States and around the world would enable the
technology to be used in more water supply alternatives.
Within the United States, recharge of water through ASR systems is regulated under
the Federal Underground Injection Control (UIC) Program. The UIC program was
promulgated in 1983 under the Safe Drinking Water Act (SDWA) under 40 CFR 144 and
146.1 The UIC program and its subsequent amendments were designed to protect current
and future underground sources of drinking water. This program is ultimately
administered by the U. S. Environmental Protection Agency but management of the
program has been delegated to 40 out of the 50 United States (AWWA, 2002), including
Florida. The UIC regulations segregate injection wells into five classes from I to V.2
ASR wells are regulated as Class V wells and are listed specifically in legislation, as
"inj section wells not included in Classes I to IV."3 ASR wells are regulated under this
S42 United States Code 300f and 48 Federal Register 14189, April 1983
2 40 Code of Federal Regulations 146.5
3 40 Code of Federal Regulations 146.5 (e)
authority. In Florida, ASR wells are defined as "wells not included in the other well
classes which generally inj ect non-hazardous fluid into or above an underground source
of drinking water" (Florida Administrative Code, 2003).4
A recent study by the U.S. EPA identified 23 categories of Class V wells including
septic tank systems, wells that drain storm-water and wastewater, and wells that dispose
of mining wastes (EPA, 1999a). The U.S. EPA devoted report volumes to each of the 23
different categories of Class V wells. Volume 21 of the series is dedicated to ASR wells
(EPA, 1999b). The U.S. EPA documented 130 ASR wells within the United States
(EPA, 1999b). Whereas the other Class V well types generally recharge untreated
waters, ASR facilities require treatment of inj ected water to primary and secondary
drinking water standards. Another regulatory impediment for ASR facilities is that
treatment may also be required upon subsequent recovery of the recharged waters. This
requirement may obligate the owner to invest additional capital to ensure proper
disinfection or aeration of the recovered waters. Recovered water-quality criteria depend
on its intended use either as a potable supply, or as surface water to meet irrigation or
environmental demands. In Florida, the most common use of the recovered water is for
potable supply. However, its use for large-scale environmental restoration is under
consideration (USACE and SFWMD, 1999).
These regulatory criteria were promulgated to ensure protection of human health
and are intended for application at municipal, private or agricultural water plants
supplying water to human customers. ASR technology can also be utilized as a water
management option to meet in-stream environmental demands. The proposed Everglades
4 An underground source of drinking water has a TDS value of less than 10,000 mg/1
Restoration ASR program proposes to use ASR technology in this manner (USACE and
SFWMD, 1999). ASR recovered water that is discharged into surface-water for
subsequent environmental distribution must conform to both Federal and state regulatory
criteria, and the National Pollution Discharge Elimination System (NPDES), both
governed by the Clean Water Act of 1970.5 These regulations provide numerical
definition of inorganic, organic and radionuclide analytes, microbiological pathogens,
dissolved oxygen, temperature, and various physical parameters for all waters. Brackish
water ASR sites may be hindered by recovered water limitations. In many states,
surface-water bodies have been divided among various "classes" of regulation. In the
case of Florida, the various classes of surface-water are described in the Florida
Administrative Code (Florida Administrative Code, 1996) and include five maj or sub-
divisions as follows:
* Class I Potable water supply
* Class II Shellfish propagation and harvesting
* Class III Recreation, propagation and maintenance of a healthy, well-balanced
population of fish and wildlife; predominantly fresh waters
* Class III Recreation, propagation and maintenance of a healthy, well-balanced
population of fish and wildlife; predominantly marine waters
* Class IV Agricultural water supplies
* Class V Navigation, utility and industrial use
Most water bodies in Florida have been categorized according to one of the five
major sub-divisions. Generally, Class I, II and III provide for the most stringent
5 Public Law 107-303 promulgated in 1970
Texas, California, Florida and Arizona have specific regulations encouraging
owners of ASR to reuse wastewater effluent as part of their proj ects. Arizona allows
users of such water to use the water rights to "extinction" (AWWA, 2002). Several states
are considering ASR-specific legislation. The state of Washington has published specific
rule changes in Chapter 173-157 of the Washington Administrative Code (McChesney,
2001). The rule establishes standards for review of ASR proposals and mitigation of any
adverse impacts in the following areas:
* Aquifer vulnerability and hydraulic continuity
* Potential impairment of existing water rights
* Geotechnical impacts and aquifer boundaries and characteristics
* Chemical compatibility of surface and ground waters
* Recharge and recovery treatment requirements
* System operation
* Water rights and ownership of water stored for recovery
* Environmental impacts
Georgia is currently the only state in the United States that has specifically
prohibited ASR by statute. Currently, the Georgia Environmental Protection Division
(EPD) is completing studies of ASR proj ects to determine if the ASR development
moratorium should be lifted (AWWA, 2002).
Non-traditional water demands include non-contact cooling water or ecological
supply. Both of these demand types may require special considerations in order to supply
suitable water. Temperature of the supplied water may also be important (EPA, 1977).
Extensive work has been conducted to explore the potential harmful effects of
temperature changes of natural waters on freshwater fish (Coutant, 1970). Several
western states including Colorado and Oregon have recently promulgated new
temperature control regulations to help native fish populations (CWQF, 2003). For all
proj ects, ecological safeguards should be an integral component of any water supply
decision process (Zarbock et al. 2001).
Any ASR proj ect of environmental significance may also be subj ect to requirements
under the National Environmental Policy Act (NEPA) of 1970. The NEPA process is
utilized to determine if environmental impacts of a proposed proj ect are significant.
Projects with significant environmental impacts may involve mitigation of impacts or
deferral of the project altogether. Federal water resources projects undertaken by the
Bureau of Reclamation, Soil Conservation Service (now the National Resource
Conservation Service), Tennessee Valley Authority, or the U.S. Army Corps of
Engineers, are subj ect to NEPA for all proj ects considered. The U. S. Water Resources
Council determined that environmental impacts should be weighed carefully when
considering water resources project planning (U. S. Water Resources Council, 1983).
In the future, additional regulation of surface-waters in the United States may lead
to ever more stringent discharge requirements. The United States Environmental
Protection Agency proposed the development of the Water Quality Criteria and Standards
Plan Priorities for the Future (EPA, 1998). The National surface water quality
protection program is a key component of EPA long term planning. This plan describes
six new criteria and standards initiatives that EPA and the States will develop over the
next decade. The Plan will integrate biocriteria, nutrient criteria, temperature control and
microbial pathogen control with improved chemical-specific and whole effluent toxicity
criteria into a water quality criteria and standards program that better ensures the
protection of human health and the improvement of surface water quality. The criteria
and standards will focus on the following six priority areas:
* developing nutrient criteria and assessment methods to better protect aquatic life
and human health;
* developing microbial pathogen criteria to better protect human health during water
* completing development of bio-criteria as a basis for aquatic life protection
* maintaining and strengthening the existing ambient water quality criteria for waters
* evaluating possible criteria initiatives for excessive sedimentation, flow alterations
and wildlife; and,
* developing improved water quality modeling tools to better translate water quality
standards into implementable control strategies.
It is obvious that many of these focus areas could impact future ASR proj ect
development. In the future, it is hoped that regulatory agencies will consider multi-media
ASR permits or something similar to simplify the permitting process but still protect
human health and the environment. Consolidation of the regulatory framework would
lead to more consistent rulings and cost effective water supply solutions (Rogers and
Louis, 2002). The issuing of multi-media permits or a consolidated permit for brackish
water ASR sites could, in part, be based upon a sound ASR planning decision framework
developed as part of this research proj ect.
ASR proj ect regulation has been a growing subj ect outside of the United States
also. Regulatory aspects relating to licensing and charging of ASR schemes are relatively
untested in the United Kingdom (Jones et al. 1998). Scientists in the Netherlands,
Australia and the Middle East also appear to be grappling with regulatory inconsistencies
or misunderstandings (Dillon and Pavelic, 1998). According to Jones, ASR proponents
in the United Kingdom must also contend with European Union regulations regarding
recharge water quality, and the potential environmental impact of any proposed scheme
(Jones et al. 1999). In Europe, aquifer recharge projects have been conducted for many
years, however the experience related to ASR proj ects is much shorter. There is little
experience in using or authorizing ASR proj ects under existing legislation (Jones et al.
ASR Use and Constraints
ASR proj ects are utilized in three broad areas to augment water supplies. The
largest and most common use of ASR proj ects is in support of potable water supply
proj ects. The second most common use of ASR proj ects is in support of agriculture in
the form of irrigation water supply. The newest alternative use for ASR is in support of
environmental water supply to support in-stream uses. Each of these categories presents
great opportunities to exploit ASR technology, however, each option is subj ect to many
constraints. The primary constraints can be grouped into four general categories
* Regulatory (discussed previously)
* Recharge and recovered water quality
* Water availability and demand
* Availability of a suitable storage aquifer
As discussed previously, regulatory thresholds usually dictate limitations on the use
of the source water and the recovered water based upon its quality. In addition to the
required regulatory thresholds, the end use of the water is of particular importance.
Although water may meet all regulatory requirements, recovered water use may be
constrained by one or more constituents contained within the water. For instance,
recovered water containing moderate amounts of sodium or boron may preclude the use
of the water for irrigating certain crops (Rhoades et al. 1992). Environmental use of the
water could be questionable where recovered water contains low concentrations of heavy
metals such as selenium or copper. Potable use may be constrained in cases where
disinfection by-products form in-situ due to the presence of residual chlorine in the
source water. It is evident that water quality constraints may vary for the three primary
ASR types. Further information and discussion on the different water quality issues is
provided in subsequent parts of this report. All ASR projects are subject to regulatory
restrictions under the UIC program and the Clean Water Act. Any ASR use will be
constrained by lack of available water or in cases of poor demand. Lastly, the ASR type
is irrelevant if a suitable storage aquifer does not exist where excess water can be stored.
Table 1-2 provides a listing of the constraints versus ASR type.
Table 1-2. Primary constraints for different ASR uses
Constraint Potable ASR Agricultural or Environmental or
Proj ect Type Irrigation Proj ect Type In-stream Proj ect
Regulatory X X X
Suitable Aauifer X X X
Water Availability X X X
Water Demand X X X
Water Quality X X Usually not a
Conventional problem with the
parameters exception of
Water Quality X X X
Water Quality X X
Water Quality X X X
Water Quality Unknown Unknown X
*A wide variety of these substances have been identified in the world's water.
In summary, in reviewing the four primary constraints to ASR use, water quality is
most sensitive to the actual use of the water. The ensuing paragraphs provide a more
detailed discussion of the various water quality issues at stake for the three ASR proj ect
types. Source water and recovered water quality can be categorized into five areas of
interest as noted in Table 1-2 including:
* Conventional parameters
* Disinfection by-products
* Emerging contaminants
Conventional parameters include total suspended solids (TSS), turbidity, alkalinity,
color, chloride, sulfate and total dissolved solids (TDS). These parameters are typically
regulated to reduce taste, appearance and odor concerns for potable water users. For
ASR systems, they are also important in evaluating potential for well clogging or other
operational problems. Besides the actual clogging of the injection well, excess suspended
solids or color can lead to changes in water quality precipitated by native aquifer bacteria.
In addition, excess color and suspended solids can make other water treatment steps more
difficult. For instance, highly colored water may clog sand filters; render ultraviolet
(UV) disinfection systems ineffective or lead to the formation of undesirable disinfection
by-products. Unfortunately, the use of storm water presents waters with these
problematic substances at high concentrations. If the conventional water quality
parameters of the source water are manageable, attention must be paid to the various
organic and inorganic toxics that may be present. As was reported earlier, the EPA under
the SDWA regulates approximately 80 parameters. There are numerous chemical
contaminants that are produced by man-induced activities. Some examples of these
include herbicides, pesticides, fertilizers, paints, fuels, etc. Some of these contaminants
may end up in storm sewers in urban areas or drainage ditches of large agricultural areas.
Many of these anthropogenic compounds are associated with known human health
effects. Generally, these are not a concern at ASR sites where the source water is potable
water pretreated to meet all primary compounds listed in the SDWA. Toxics may be
more problematic if only partially treated storm water or reclaimed water is the ASR
source water for storage. Another type of toxic of concern is a toxin created by blue-
green algae (Carmichael, 2001). Blue-green algae, also known as cyanobacteria, can
form dense growths in mesotrophic, eutrophic, and hypereutrophic waters when the
following conditions exist (Carmichael, 2001):
* High nutrients the cyanobacteria outcompete other algae for available nitrogen
* Temperature the cyanobacteria have a higher optimum temperature than green
* Light the cyanobacteria grow better at lower light levels than other algae
* Biological the cyanobacteria have fewer natural enemies, thus lower predation
rates, and their ability to float prevents sedimentation
The cyanobacteria can produce taste and odor problems in water as well as natural
toxins. The toxins, called cyanotoxins, have been shown to cause acute toxicity and
lethality to animals and humans (Carmichael, 2001). Surveys were completed in 1996 to
1998 to determine the presence of the toxin microcystin. Of 677 water samples that were
collected at multiple utilities in the United States and Canada, 80% were positive for
microcystin (Carmichael, 2001).
Pathogens and disinfection by-products are generally highly inter-related. The term
microbe refers to living organisms too small to see with the naked eye. Pathogens are a
type of microbe that may cause disease (Schueler, 1999). Examples of disease bearing
* Shigella spp. (dysentery)
* Salmonella spp. (gastrointestinal illness)
* Pseudomonas aeruginosa (swimmers itch)
Some sub-species can cause cholera, typhoid fever and staph infections (Schueler,
1999). The risk of contracting a disease from a pathogen depends upon many factors
* Method of exposure
* Pathogen concentration
* Incubation period
* Age and health of person exposed
Protozoa are single-celled organisms that are motile. Examples include Giardia
Lamblia and Cryptosporidium. To infect new hosts, these critters create hard casings
known as cysts (Giardia) or oocysts (Crypto) that are shed in feces, and travel through
surface waters in search of a host. The cysts or oocysts are very persistent and can
remain viable for many months (Pitt, 1998; Schueler, 1999).
Pathogens are generally a target of water treatment efforts using various methods of
disinfection. The most common method of disinfection is the use of chlorination.
Chlorine gas is a powerful oxidizer that inactivates the pathogen, rendering it harmless.
Unfortunately, a vast maj ority of water treatment plants within the United States utilize
some form of chlorination as the mechanism to achieve disinfection. The chlorination
process will create disinfection by-products (DBPs) in water containing color and natural
organic (Krasner et al., 1989). The primary families of DBPs produced during
chlorination include trihalomethanes (THMs) and haloacetic acids (HAAs). Ozonation is
another popular method of disinfection. Ozonation primarily forms only one particular
DBP, bromate, however, it can also create recharge water that is super-saturated with
oxygen contributing to possible geochemical reactions in the aquifer. Ultraviolet
radiation (UV) can also be utilized for disinfection purposes as long as the UV energy is
not absorbed or refracted by highly colored waters (Farrell and Burris, 1995). Other
alternative oxidizers include chlorine dioxide and chloramines. All disinfectants and
disinfection by-products are regulated by the USEPA under the Stage 1 Disinfectants and
Disinfection Byproducts Rule (EPA, 2001).
The National Research Council (1994) cites work done by Bull et al. (1990) to
compare the risks from disinfection by-products versus risks from pathogens (which
would likely be present without disinfection). Bull et al. (1990) determined that the
probability of mortality induced by improperly disinfected drinking water would exceed
the carcinogenic risks introduced by DBPs by as much as 1,000-fold.
Besides DBPs, a new water quality concern has arisen related to a class of
contaminants called "emerging contaminants". Emerging contaminants are generally
man-made pharmaceutical and chemical compounds including drugs, hormones,
antibiotics, caffeine, nicotine, etc. A majority of these substances have been found in
wastewater around the world (Montague, 1999). It has long been recognized that sludge
from sewage treatment plants contained aspirin, caffeine, and nicotine (Daughton and
Ternes, 1999), but it has been work performed by European scientists who have
uncovered the real magnitude of the problem (Buser et al. 1998). The effect of these
compounds on human health is unknown today. More worrisome is the effect of these
compounds on the environment. Environmental users may be more sensitive to low
concentrations of certain contaminants than human users.
ASR proj ects are dominated by potable water supply uses. Potable water proj ects
provide water to both large urban centers (Reese, 2002) as well as rural towns (Murray,
2004). Potable water supply ASR proj ects typically are co-located with existing water
treatment plants (CH2M Hill, 2002).
Usually, the existing water plants are not fully utilized during off peak times.
During off peak times, water demand may be only a fraction of daytime demand.
Therefore, water is available for ASR storage during this time. In addition, this water is
pre-treated in order to meet all primary and secondary standards under the SDWA.
Generally, water quality concerns are focused upon the generation of DBPs from
chlorination or ozonation, release of heavy metals from geochemical reactions (Mirecki,
2004), or the potential effects of various emerging contaminants. Although all potable
water ASR proj ects are required to meet regulatory limits for DBPs, residual chlorine
dissolved in the ASR recharge water can continue to form DBPs in the storage aquifer
(Fram et al. 2002). Recharge water containing high levels of oxygen and dissolved
organic carbon can release low concentrations of various heavy metals such as arsenic,
manganese, iron, cobalt, nickel, or mercury (Johnson et al. 1998). The water treatment
plant associated with the ASR proj ect may not be capable of removing certain heavy
metals upon recovery of stored water. Emerging contaminants pose a similar problem.
As the risks from emerging contaminants become better understood, their removal
and treatment will become a focal point of research. Some work has already been
completed along these lines. Drewes et al. (2002) has shown that removal of anti-
epileptic drugs could be accomplished through the use of nanofiltration or reverse
osmosis. Raloff (1998) discusses a recent finding that running water through activated-
carbon filters removed all vestiges of the personal care products (PPCPs). Ternes
confirmed that activated carbon and ozone removed several PPCPs efficiently (Ternes,
Agricultural and Irrigation Use
After potable water use, the most common type of ASR proj ect is in support of
agricultural irrigation. ASR proj ects developed in support of agriculture may have less
onerous regulatory burdens since water quality restrictions may be lessened (NRC, 1994).
Australian researchers have pioneered the use of ASR proj ects for irrigation purposes
(Barry et al. 2002).
The use of AR or ASR wells to supply irrigation water is fairly common in arid
regions (Bureau of Reclamation, 1996b). The water quality of the recovered water
typically dictates the overall effectiveness of this option. In regions where the ambient
aquifer water quality is good, the use of the recovered water is usually not restricted. In
the case of brackish water aquifers, the recovered water is a mix of inj ected and ambient
groundwater. Therefore, over time the concentrations of total dissolved solids (TDS) in
the recovered water increases until it exceeds accepted regulatory thresholds. The United
Nations has conducted significant research in the use of such saline water for irrigation
purposes (Rhoades et al. 1992). The principal effects of higher TDS water used for
irrigation can range from acute plant stress, decreased crop yield, waterlogged soils, clay
swelling, or clay dispersion. Although water containing TDS values as high as 7,000
mg/1 have been utilized for irrigation in certain desert areas, the United Nations has
focused upon the beneficial use of "slightly saline" water with TDS concentrations
ranging from 500 to 1,500 mg/1. Water with those attributes is utilized all over the world
(Rhoades et al. 1992). In addition to restrictions related to salinity, certain emerging
contaminants and toxics may also need close scrutiny prior to recommending any ASR
An estimated 40% of the antibiotics produced in the United States are fed to
livestock as growth enhancers (Raloff, 1998). For ASR projects that utilize storm water,
this may be a significant finding and may be an important consideration for system site
selection. Manure that contains similar compounds is also routinely spread onto
agricultural fields where the compounds can then get washed into surface water or
percolate into groundwater (University of Arizona, 2000). Presumably, ASR proj ects
selected for irrigation use will be sited near existing agricultural areas; therefore,
emerging contaminants may be present in the source water.
In-stream and Environmental Use
The use of ASR proj ects to support environmental demands will be an important
water supply component in the future. It is already being considered to assist with the
restoration of the Everglades ecosystem (USACE and SFWMD, 1999). Unfortunately,
the environmental effects of ASR use in this manner are generally unknown. As with the
other two ASR types, water quality issues will most likely be the largest constraint to
mass use of ASR in in-stream proj ects. Certainly, ASR could be beneficial in improving
water supply, distribution and timing for environmental users. Further research in this
area may allow additional proj ects to be undertaken in this category.
Environmental users may be sensitive to changes in temperature, introduction of
toxics, disinfection by-products, and any number of emerging contaminants. Once these
contaminants are introduced into surface water or groundwater, environmental receptors
may be at risk. For example, nitro musks, used as a fragrance in many cosmetics, have
attracted concern because of their persistence and possible adverse environmental
impacts (University of Arizona, 2000). Purdom et al. (1994) documented hormonal
effects in fish related to exposure to ethinyloestriadiol (component of contraceptive pills)
at concentrations as low as 0.1 ng/1. Studies at Stanford University's Hopkins Marine
Station expressed concern about new drugs called efflux-pump inhibitors. Designed to
keep microbes from ej ecting antibiotics intended to kill them, they also seem to impede
the cellular pumps that nearly all animals use to get rid of toxicants (Raloff, 2000). In a
recent symposium on the subj ect, scientists noted that the biggest risks from PPCPs are
for aquatic life, not humans (Raloff, 2000). More recent articles echo this thought and
recognize the lack of knowledge in this area (Khan and Rorij e, 2002). The long-term
synergistic effect of these PPCPs on human or ecological health is not known today.
Research has been focused upon a few of the most problematic compounds including
endocrine disrupters and antibiotics. Endocrine disrupters have the potential to interfere
with the production of various hormones that regulate bodily functions. A multitude of
endocrine disrupters has been identified in natural waters (Khan and Rorij e, 2002). To
some scientists the release of antibiotics into natural waterways is even more worrisome
(University of Arizona, 2000). The release of antibiotics may result in development of
disease resistant bacteria in the various waterways. A number of antibiotics have been
positively identified in streams within the United States (Kolpin, 2002).
ASR PLANNING MEANS AND METHODS
Current Planning Methodology of ASR Proj ects
ASR proj ect planning consists of multiple parts and iterations. Many planning
factors need to be evaluated to determine the ultimate feasibility of a prospective proj ect.
As ASR projects are located throughout the world in diverse environments, no two
projects are alike. However, many sites share common issues, constraints or problems.
A maj ority of these can be determined through judicious review of the relevant ASR
literature including operating site data. Based upon a thorough review of the available
literature by the author, no comprehensive ASR site comparison has been completed
anywhere in the world. Several investigators (Pyne, 1998; Pavelic, 2002) have compiled
information for a limited number of sites to analyze specific ASR issues but no
comprehensive evaluation has been completed. Comparisons among brackish water ASR
sites are even less available in the literature. A comprehensive comparison of site data
would provide an impetus for the development of a new brackish water ASR planning
decision framework. According to Grigg (1996), a coordinated framework "provides a
structure for the players to work under, a set of process rules, and a reporting procedure".
Grigg goes on to describe additional attributes widely recognized as essential for
management actions based upon decision frameworks including the use of effective tools;
the basing of actions on scientific and risk assessment; the use of measures to reduce
uncertainty; and the selection of financially feasible approaches.
In reviewing existing ASR planning methodologies, one thing becomes abundantly
clear; no two sites are treated the same and only limited standardization exists. ASR has
been investigated all over the world in all manner of hydrogeologic environments. For
most sites, planning has followed recommendations provided in several widely utilized
reference books on artificial recharge of groundwater (Asano, 1985; National Research
Council, 1994; ASCE, 2001). A limited number of project teams also consulted the only
known reference book specifically focused upon ASR projects (Pyne, 1995). In the
United States, planning of artificial recharge proj ects became better-coordinated
following passage of the High Plains States Groundwater Demonstration Program Act of
1983.1 This act directed the Secretary of the Interior, acting through the Bureau of
Reclamation and in conjunction with the Administrator of the Environmental Protection
Agency, to explore the benefits and impacts of artificial recharge proj ects in the western
United States. Over 13 separate projects have been carried out, with some still ongoing
(Bureau of Reclamation, 1996). The various projects utilized available surface water to
recharge both unconfined and confined (artesian) aquifers in a variety of hydrogeologic
environments using a myriad of artificial recharge techniques. Both surface spreading
techniques (Wilson, 1979) and well injection techniques (Bichara, 1974) were tested and
monitored. Several of the proj ects also included recovery of the recharged water similar
to ASR projects (Bureau of Reclamation, 1994; Bureau of Reclamation, 1996b). Similar
studies were underway in Florida through cooperative efforts by the U.S. Army Corps of
Engineers and the United States Geological Survey (Merritt et al. 1983). The initial
planning methodologies utilized by the Bureau of Reclamation, United States Geological
SPublic Law 98-434 promulgated in 1983
Survey and the U. S. Army Corps of Engineers provide a good starting basis for
conducting ASR proj ects. Updating and refining this planning methodology based upon
new case-study information would be useful. As an example, the Highline Well Field
ASR Demonstration Proj ect (Bureau of Reclamation, 1994) focused planning on the
following key issues:
* Water System and availability of water
* Hydrogeologic considerations
* Regulatory considerations
* Water Quality considerations (source water and recovered water)
* Well clogging considerations
* Geotechnical considerations
* Economic evaluation
Of these, geotechnical considerations were only briefly reviewed, while water
quality considerations were investigated in a very high level of detail. This level of effort
disparity is common among the planning efforts for both the artificial recharge and ASR
proj ects reviewed for this proposal. The investigation effort afforded each planning issue
is somewhat dependent upon the agency responsible for performing the investigations.
Federal agencies like the Bureau, Corps or USGS, tend to look at all aspects of a problem
while private companies may weigh cost and risk issues when determining what to focus
upon. Although planning for ASR projects has marginally improved since early efforts,
each proj ect is still conducted as a single entity without much regard to what has been
successful or what has failed at other projects. Similar to the Seattle project, other recent
proj ects provide a good illustration of the current planning methodology.
The city of Green Bay, Wisconsin had a preliminary ASR feasibility evaluation
completed to evaluate the potential for ASR in the region (CH2M Hill, 1999). The final
report reviewed the applicability of ASR in the Wisconsin region. According to the
report, ASR applicability is governed by three principal criteria:
Variability must occur in water supply, water demand, or water quality. Planned,
useful recovery capacity should be sufficient to justify the initial investment; typically,
ultimate capacity should exceed one MGD to be cost effective. A suitable aquifer must
be available for water storage. Suitability may be defined in terms of hydraulic
characteristics, depth, groundwater quality, geochemistry, competing users, and other
criteria. In order to evaluate the three criteria, the following planning factors were
* Source water supply
* Source water quality
* Water demand
* Geology and hydrogeology
* Other groundwater users
An ASR demonstration proj ect in the vicinity of Des Moines, Iowa was conducted
in two phases between 1995 and 1998. The first phase was the development of
preliminary engineering feasibility evaluation, while the second phase involved
demonstration pilot testing of an ASR system. Miller et al. (1998) discusses the proj ect
in detail. The study evaluated similar planning factors discussed previously related to the
Green Bay, Wisconsin ASR proj ect. The planning factors investigated included:
* Water supply
* Water demand
* Geology and hydrogeology
* Permitting requirements
* Environmental impacts
* Engineering requirements
* Well performance factors (e.g., hydraulics, well clogging potential)
* Water quality
Anglican Water Services completed a regional feasibility scoping study to evaluate
ASR potential in their various service areas (Jones et al. 1999). They investigated
limestone, greensand, chalk, sandstone, and sand aquifers. They considered:
* Hydraulic properties
* Structure controls
* Available storage
* Availability of recharge water
The study concluded that the Chalk Aquifer and the Lower Greensand Aquifer were
the most promising areas. They then evaluated five sites for the Chalk Aquifer using a
desktop site selection study. The merits of the alternative sites were evaluated using an
analytical decision model. They used several planning criteria:
* Available Infrastructure
* Potential for future ASR development
Jones et al. utilized these criteria to select the Balkerne (Colchester) site and
Foxhall (Ipswich) as being most suitable. Unfortunately, desktop studies led to the
conclusion that significant additional site infrastructure would be required at each site.
Therefore, the existing Horkesley Water Treatment Works was selected for ASR testing
in a pilot study.
Murray (2004) lists several AR planning success factors including:
* Quantity, type and reliability of the water source available for recharge
* The quality of recharge water, aquifer geochemistry, the compatibility of the two
waters, and aquifer clogging issues high quality, low turbidity water can be used
successfully in any kind of recharge system.
* The hydraulic characteristics of the aquifer and groundwater recovery
* Management requirements
Oklahoma State University used multiple planning factors in its evaluation of
artificial recharge feasibility in Northwestern Oklahoma (Pettyj ohn and White, 1985)
* Source of recharge water
* Proximity to source
* Permeability of near-surface materials
* Quality of source
* Quality of water in the aquifer
* Availability of source water
Both water quality and source water availability was considered to be of paramount
importance similar to the Seattle, Green Bay, and Iowa studies discussed previously. The
Oklahoma State study also showed the value of using site selection criteria to develop
"overlay" maps of potential recharge sites. Overlay planning methodology is an
acceptable system to use for ASR planning or site selection evaluations. Overlay
methodology has been utilized by many Federal and State agencies and is discussed in
more detail by Focazio et al. (2002).
Both the south Denver Basin aquifer recharge demo proj ect (Bureau of
Reclamation, 1997) and the Washoe County, Nevada recharge demo proj ect (Bureau of
Reclamation, 1996) included both regulatory and institutional considerations in their
planning efforts. The St. Johns River Water Management District utilized both site
selection criteria (overlay methodology) and institutional/regulatory considerations in
locating new rapid infiltration basins (Rabbani and Munch, 2000). Many of the projects
discussed herein also utilized numerical or analytical modeling to aid in the evaluation of
proj ect impacts or for estimating benefits. Of the proj ects reviewed, those that utilized
numerical models as planning tools provided the most complete comparison of proj ect
benefits and costs.
In planning ASR proj ects in Portland, Oregon, the Portland Water Works included
ASR as part of the Portland area Regional Water Supply Plan so that it could be
compared to other water supply options instead of evaluated by itself (Portland Water
Works, 2001). The planning efforts reviewed all key proj ect constraints but focused
resources upon water quality and effects on the environment because both were key
policy priority areas. Whereas the Seattle proj ect viewed ASR by itself, the Portland
approach is more holistic. It regarded ASR as another option for its water supply needs.
Any new decision framework should include metrics that allow comparisons of ASR to
other more traditional water supply options.
Most of the proj ect planning efforts included some type of pilot study to determine
the final efficacy of an artificial recharge or ASR proj ect. Piloting at test sites may be
warranted but should be considered carefully. Pyne (1995), Mirecki et al. (1997) and
Miller et al. (1998) all relate methodologies and lessons learned through the conduct of
pilot tests and the correlation of data to make decisions on larger-scale ASR
implementation. Butts (2002, p. 24) notes
any successful long-term ASR proj ect will have had a pilot study of some type
performed before final design, construction, and implementation of the full-scale
The South Florida Water Management District and the U.S. Army Corps of
Engineers whole-heartedly support the notion of using ASR pilot wells to assist with
system scale-up (USACE and SFWMD, 2003). Pilot projects were instrumental in the
planning for an ASR proj ect in Chesapeake, Virginia (Dwarkanath and Ibison, 1991).
The ASCE Standard Guidelines for Artificial Recharge cautions that ASR pilot proj ect
well sites should be selected with care to ensure that results can be extrapolated to the
entire recharge area (ASCE, 2001). This cautionary statement is especially important for
large ASR well field projects where conditions and planning constraints vary spatially
across the proj ect area. For brackish water ASR sites, piloting can be expensive and
difficult due to recovery and management of brackish water. In a review of brackish
water ASR sites for this report, the author has not uncovered one case of a proposed
proj ect that, after initial feasibility studies, was not recommended for pilot testing.
Again, this seems to be symptomatic of incomplete feasibility level ASR planning of
these sites. The current planning methodology for brackish water ASR sites seems more
experience based rather than following a standardized method.
Planning at Non-brackish Water ASR Sites
In these ASR sites, freshwater from excess storm water or wastewater, is inj ected
into permeable groundwater aquifers for later withdrawal. The aquifers in question may
be available for artificial recharge for many different reasons. The aquifers may be over
drafted as a result of pumpage in excess of the aquifer safe yield. The aquifer may not be
utilized for potable water supply due to obj ectionable quantities of various constituents
such as sulfate, iron, manganese, radon, or others dissolved in the ambient groundwater.
Water availability from the aquifer may not be dependable as a water supply due to
seasonality of flow or recharge. These aquifers present a tremendous opportunity for
artificial recharge or ASR projects. In essence, these aquifers offer an untapped resource
that provided the proper conditioning, may provide a cost-effective water resources
Planning at Brackish Water ASR Sites
In these ASR sites, freshwater from excess storm water or wastewater, is inj ected
into aquifers with brackish groundwater. According to Drever (1997), brackish waters
have total dissolved solids concentrations of between 1,000 to 20,000 mg//1. During
aquifer recharge operations, the inj ected freshwater mixes with the poorer-quality
ambient groundwater. Mixing is due to advection, hydrodynamic dispersion, and
buoyancy stratification. During recovery periods, the recovered water is a mix of the
inj ected and ambient water. Typically, the recovery of the water is halted once the water
quality surpasses a regulated value.
In many cases ASR projects can succeed in storing excess water to meet quantity
demands but are somewhat limited due to regulatory limitations or use restrictions. The
water that can be provided by an ASR system must provide both the quantity and quality
required for a particular use. ASR systems may use either groundwater sources or
surface water sources. Frequently, surface water sources offer water quality advantages
over groundwater sources (Lucas and McGill, 2002). The quality of the water source can
sometimes control the process. For instance, potential well locations in urban areas may
be subj ect to contamination from industrial activities or other anthropogenic sources.
Locating ASR wells in rural areas must take into consideration likely non-point source
contamination emanating from agricultural areas. Herbicides, pesticides, and fertilizers
can all pollute source waters in potential project areas. Although pristine areas may not
exist near water sources or system demands, consideration should be given to source
water quality. In general, for brackish water ASR sites, a complex interplay between the
source water quality and the ambient groundwater quality, controls the proj ect feasibility.
Frequently, these types of ASR sites are more challenging to plan, construct and operate.
Planning of these sites has been especially unreliable and problematic. Existing sites
range from those that are highly successful to those that are questionable both from an
economic and an environmental perspective. Planning for these sites is often hindered by
the lack of available performance metrics. Additional research is required to develop
appropriate planning performance metrics for brackish water ASR sites.
Formulation of an Improved Planning Methodology
Review of ASR Performance Factors
The performance of an ASR system is controlled by a complex interaction among
many variables. It has been explored through examination of existing site data,
development of physical models, through development of simple analytical models, and
through development of numerical models. ASR performance factors can be sub-divided
into several categories. First, many ASR performance factors are dependent upon the
intrinsic physical properties of the aquifer storage zone selected including hydraulic
conductivity, porosity, thickness, heterogeneity, strength of aquifer materials, character of
aquifer zone, dispersivity, and tortuosity. In confined aquifer environments, intrinsic
physical properties of the confining units may also be relevant performance factors.
Another category of ASR performance factors is linked to boundary conditions present at
the well site including pre-existing aquifer gradient and density of water in the storage
zone. A third category of ASR performance factors is linked to geochemical reactions
that may occur in the aquifer after introduction of inj ected source water. A last category
of ASR performance factors is dependent upon site operational considerations including
inj section rate and volume, quality of the source water, type of source water pre-treatment,
storage duration, and well design. The degree of importance of each of the performance
factors may be different for aquifers characterized as "non-brackish"2 Or "brackish". For
instance, in brackish water environments, the density of ambient groundwater in the
storage zone may lead to buoyancy stratifieation of the inj ected freshwater; the
stratifieation can reduce recoverability of the freshwater.
2 Ambient total dissolved solids (TDS) concentration less than 1,000 mg/1
Frequently, a combination of performance factors or their interaction may form the
basis for a performance guideline or metric. The development of recommended ASR
performance metrics will be based upon an evaluation of ASR performance factors and
constraints. Recommended performance guidelines and metrics are discussed in Chapter
3 of this research report.
General discussion of all ASR sites
For all ASR proj ects, performance factors relating to the aquifer itself are
important. The aquifer hydrogeology will control the distribution of the inj ected water
within the aquifer storage zone. The aquifer hydraulic conductivity controls the
distribution of water level or potential (pressure) in the aquifer. Aquifers exhibiting low
to moderate hydraulic conductivity may result in induced high water levels or aquifer
pressure. Inordinately high water levels may result in surface flooding or loss of inj ected
water through surface runoff. Inordinately high aquifer pressures may result in local
hydraulic fracturing of the aquifer material itself or surrounding confining units in the
case of a confined aquifer (Hubbert and Willis, 1957).
Aquifers exhibiting low porosity or aquifers where fluid flow is concentrated in
fractures rather than aquifer pore space, may increase groundwater flow velocity or may
induce high rates of diffusion (Gale, 2002; Anderson and Lowry, 2004); either of these
phenomena may reduce recoverability of inj ected water.
The character and structure of an aquifer may lead to heterogeneity of the intrinsic
properties. Many aquifers are not true "ideal" porous media and are subject to
nonidealities (Alpay, 1972). Examples of nonidealities given by Alpay include:
* Pore size distribution
* Dead-end pore space (disconnected pores)
* Geologic stratifieation
* Non uniform permeability
* Directional permeability
* Geologic structural framework (e.g., faults, dipping strata)
* Geologic stratigraphic framework (e.g., bar deposits, channel fills, glacial features)
These various factors can also lead to complicated diffusion pathways or enhanced
mechanical dispersion (Domenico and Schwartz, 1998). Mechanical dispersion is mixing
caused by local variations in velocity. Mechanical dispersion is an "advective" process
and is discussed by Anderson (1984) and Sudicky (1986). At Hield scale, it appears that
dispersivities increase with scale up to an asymptotic limit (Gelhar et al., 1992). At any
given scale, dispersivities in the longitudinal direction (primary flow direction) can range
over two to three orders of magnitude depending on the variability in hydraulic
conductivity (Gelhar et al. 1992). Schulze-Makuch (2005) updated Gelhar's work by
compiling a larger dispersivity database from various reports and literature. Schulze-
Makuch also proposes a relationship between the geologic medium and hydrodynamic
The geotechnical properties of the aquifer material may affect the ASR
performance. Aquifers confined by compressible clay units can be subjected to changes
in effective stress.3 ASR recovery operations subject the confining clay units to cyclical
effective stress changes; decreases in effective stress during ASR inj section and increases
in effective stress during recovery. Increases in effective stress can negatively affect the
3 Effective stress equals the total stress minus the aquifer pore pressure
clay confining units through subsidence or consolidation (Li and Helm, 2001; Brown et
Performance at ASR sites is often expressed as a percentage of the water inj ected
that is recovered. The most common performance metric for these sites is "recovery
efficiency," a concept first presented in the 1970s (Kimbler et al. 1975). ASR
practitioners have utilized the term "recovery efficiency" as the metric of choice to
evaluate the feasibility and cost effectiveness of prospective ASR proj ects. The
definition of recovery efficiency utilized by most researchers is the total volume of water
recovered up until the applicable regulatory limit, expressed as a percentage of the
volume injected. Equation (1) provides a mathematical representation of this concept:
(1) Recovery Efficiency (RE) = Vr/Vi X 100%
For instance, an ASR proj ect that injects 1,000,000 gallons of water and then
subsequently recovers only 100,000 gallons before regulatory discharge limits have been
exceeded has a RE of 10%. In most instances, chloride or TDS is the limiting parameter
in potable ASR projects. The use of RE is somewhat limited since it does not allow a
determination of the actual mass of inj ected water that is recovered, especially if both the
inj section water and ambient groundwater contain the parameter that is monitored.
Pavelic et al. (2002) discusses an alternate terminology using the concept of "recovered
mass." As ASR science advances, the recovered mass approach may become an
acceptable alternative metric. As of today, RE is utilized almost exclusively throughout
Streetly (1998) developed a model prototype to simulate various controls on ASR
performance in potable aquifers. Streetly used a model configured in radial format
spaced at logarithmic intervals from the ASR well to an outer boundary at 20,000 meters.
No density differences between inj ected and recovered water were applied in the model.
He utilized a standard set of basic aquifer parameters with a standard format of five, 30-
day cycles of inj ection/followed by 30 days recovery. Sensitivity runs were used to
research the effect of varying parameters by 0.25, 0.50, two, and four. For the basic set
of model simulations, Streetly used the following set of aquifer parameters:
* Transmissivity = 2, 153 ft2/day with range from 538 to 8,612
* Aquifer b = 164 with range from 41 to 656 feet
* Porosity = 0.05 with range from 0.013 to 0.20
* Dispersivity = 32.81 feet with range from 8.2 to 131 feet
* Diffusion small and can be ignored except in dual porosity aquifers
* Pumping Rate = 70,640 ft3/day with range from 17,660 to 282,559 (2. 11 MGD)
* Cycle length = 30 days with range from 8 to 120 days
* Rest or storage period between inj ection/recovery = 0 days to 30 days
Streetly concludes that dispersivity has the most dramatic effect on RE. He
concludes that permeability and diffusion have no effect on RE in a homogeneous
aquifer. Streetly keenly observes however, that the permeability and the dispersivity are
related and often associated with each other. Apart from dispersivity, key parameters
were all related to the size of the bubble of water inj ected; a larger bubble radius is
associated with a higher RE.
Streetly also shows that RE improves after each cycle but eventually reaches a state
of diminishing returns. For his standard run, RE was estimated at 66% for cycle 1 and
80% at cycle 5. His results demonstrate that thinner aquifers provide better RE
performance than thicker aquifers. For '/ of the base storage zone thickness, RE
improves to 73%; for four times the base storage zone thickness, RE declines to 57%.
The numerical results presented by Streetly clearly show that hydrodynamic dispersion
and volume inj ected into the aquifer are the most important variables. When the '/ the
base dispersivity was simulated the estimated RE was 77% while for four times the base
dispersivity resulted in a RE value of 46%. When '/ the base pump inj section rate was
simulated for 30 days the RE was predicted to be 57% while for 4 times the base
inj section rate the RE was estimated to be 73%. When the pumping rate was held constant
but the inj section period was changed, a similar set of results was revealed. This indicates
that volume inj ected is an important variable.
Anderson and Lowry (2004) performed similar numerical experiments to review the
effect of different variables on ASR performance. The performance variations were
measured using estimates of RE for each simulation tested. The obj ectives of the
research pursued by Anderson and Lowry were to (1) investigate the hydraulic
controlling factors on ASR as they relate to recovery efficiency in selected representative
hydrogeologic settings in Wisconsin; (2) develop a methodology using numerical flow
and transport models whereby the hydraulics of ASR systems can be simulated.
Anderson and Lowry found that the degree of mixing in the aquifer is a key factor
governing ASR performance. Model simulations that included advection only resulted in
much higher RE than those simulations with both advection and dispersion processes
included. In simulations tested, the RE decreased as the regional pre-existing gradient
was increased. A large pre-existing regional gradient tends to carry the inj ected water
away from the ASR well where it may not be fully recovered. Anderson and Lowry note
that this issue is even more important when small inj section volumes are considered.
Lowry (2004) discusses the results of model simulations using small inj section volumes in
combination with high regional gradients in detail. Anderson and Lowry also clearly
show that RE is inversely proportional to dispersivity; as dispersivity values increase, RE
values decrease. In addition to intrinsic aquifer properties, Anderson and Lowry also
investigated ASR storage times. Generally, as storage duration increases, RE decreases
1()() -Longitudinal Dispersivity
0 8 ft
Storage Period (Days)
Figure 2-1. The effect of storage period on recovery efficiency [modified from Anderson
and Lowry (2004)]
Anderson and Lowry found that RE consistently increased as volume of inj ected
water was increased, except for one case using an unconfined dolomite storage zone,
where recovery efficiency decreased after the initial increase. Generally, the RE
increases taper off to some asymptotic value dependent upon site-specific conditions at
each ASR proj ect site. According to Anderson and Lowry:
these results suggest that pilot tests using small volumes of inj ected water may not
be helpful in estimating recovery efficiency for the larger volumes of water used in
final operation of an ASR system. (Anderson and Lowry, 2004, p. 10)
Figure 2-2 depicts the results of model simulations where inj section volume was evaluated
(Anderson and Lowry, 2004).
20 3 [ Unconfineddolomite aqulfer
SGlacial drft aqulfer
I Confined sandstone aq~ufer
020 40 60 80 100
Volume of Injected Water (MlG)
Figure 2-2. The effect of inj section volume in million gallons on recovery efficiency
[modified from Anderson and Lowry (2004)]
Besides the ASR performance factors related to hydrogeology, ASR performance
can also be negatively affected by geochemical reactions that occur between the aquifer
matrix and the inj ected water or the ambient groundwater and the inj ected water. Gale
(2002) noted that geochemical issues were one concern that could constrain ASR
development in England. According to the EPA (1999b), the intended use or recharge
obj ective needs to be considered in evaluating quality of water required. The following
basic processes must be considered:
* Biodegradation by and growth of microorganisms
* Chemical oxidation or redox
* Sorption and ion exchange
* Chemical precipitation or dilution
* Volatilization or photochemical reactions
Geochemical issues have constrained development or resulted in site closure at
several ASR proj ects in the United States and England. Elevated levels of mercury
(Wendell and Glanzman, 1998) and fluoride (Eastwood and Stanfield, 2001) have been
noted at two of these sites. Geochemical problems have also been discovered at an ASR
site in Green Bay, Wisconsin (CH2M Hill, 2001). Castro (1995) provides a lengthy
discussion of geochemical reactions observed during cycle testing at an ASR site in
Myrtle Beach, South Carolina. Arthur et al. (2001) and Arthur et al. (2002) provide
extensive discussions of geochemical problems discovered at a few ASR sites in Florida.
The report is an evaluation of water-rock interaction at three ASR sites in southwest
Florida. The sites include Northwest Hillsborough County Reclaimed Water ASR,
Tampa Rome Avenue ASR, and the Punta Gorda ASR facility in Charlotte County.
Research focuses upon the latter two sites.
The report is a deliverable from the ongoing "Aquifer Storage and Recovery
Geochemistry Project" which has been ongoing since 1998. It was started because
preliminary geochemical laboratory leaching experiments conducted in 1995 indicated
that uranium and other metals could be leached from Floridan Aquifer System limestones
under oxidizing conditions. Source waters with higher dissolved oxygen were noted to
be particularly problematic. Arthur et al. (2002), note that a potential metal mobilization
problem is indicated when the concentration of a metal is low in both ambient and source
waters, but an increase is noted during ASR recovery. The Punta Gorda ASR site clearly
shows an increase in arsenic that is above both ambient and source waters. The same
pattern is observed at the Tampa Rome Ave ASR facility. Besides arsenic, other metals
such as iron, manganese, nickel, vanadium, and uranium are mobilized from the aquifer
system matrix into the inj ected source water and it is contained within recovered ASR
water. Arsenic and uranium mobilization are the most consistent and well-documented
trends observed in the study by Arthur et al. (2002). Preliminary results indicate that
mobilization reactions occur on the order of a few days and can sometimes also be seen
in nearby monitoring wells. During three successive tests using similar cycle test
volumes, metal concentrations decrease; however, if larger volumes are introduced that
expose virgin aquifer material, additional mobilization would be expected.
Mirecki (2004) studied geochemical data at 11 ASR sites located in south Florida.
Mirecki observed that several of the sites had elevated concentrations of arsenic,
radionuclides, ammonia, and sulfate. Seven of eleven ASR sites studied reported arsenic
results; only one of these sites reported arsenic concentrations in excess of water quality
standards. Three of the eleven sites reported ammonia concentrations in the recovered
water in excess of Florida surface water regulatory standards.
Jones et al. (1999) discuss geochemical reactions in detail and lists the most
prominent ones known:
* Adsorption onto rock or sediments; metals may have pH dependent properties
* Ion exchange clay minerals, organic matter, and oxides/hydroxides have capacity
for uptake of cations or anions. Brackish aquifers may exchange Ca+2 for Na+ and
result in sodium rich recovered water.
* Oxidation-reduction Reduction of oxygen, denitrification, reduction of nitrate,
oxidation of organic matter, oxidation of sulfide minerals, oxidation of Fe+2
leading to precipitation of iron oxides and hydroxides. Oxidation of iron sulfides
can induce an increasing acidity, thereby mobilizing metal ions (lead, cadmium).
* Dissolution and precipitation Mainly determined by the Saturation Index of the
mineral in question. If the saturation index is reached precipitation takes place.
Precipitation may lead to clogging around the well. Conversely, undersaturated
water may lead to dissolution of aquifer material.
* Reaction kinetics could control some of these issues. Kinetics may be slow and
may require longer durations to inj ection/extraction and storage to avail
themselves. Longer-term cycles are more likely to reach equilibrium between
aquifer mineralogy and recharge water. Minerals like calcite and strontianite
dissolve relatively rapidly; and the dissolution of salts like halite and sylvite occur
Arthur et al. (2002) also proposed the most probable geochemical reaction
mechanisms noted for several Florida ASR sites to be:
* Oxidation of sulfide minerals such as pyrite which may contain trace elements as
lattice substitutes (Ni, Co, Cu, Pb, As, Zn, and Mn)
* Desorption or dissolution of Fe and Mn hydroxides
* Oxidation-reduction of organic materials which can mobilize organically
* Biological transformations
Stuyfzand (1998) has studied similar geochemical issues in the Netherlands. In a
study of 11 deep well recharge experiments, oxidation of pyrite is reported resulting in
mobilization of arsenic, cobalt, and nickel. According to Stuyfzand, the main variables
affecting metal mobility include:
* Native and input water chemistry (Dissolved oxygen, pH)
* Aquifer matrix chemistry/mineralogy
* Input water matrix contact time and number of cycles
* Site-specific hydrogeology/geochemi stry
Gaus (2001) observes that maj or chemical changes to the recovered water quality
are expected when one or more of the following conditions are met:
* There is a large difference in chemical condition between the inj ected and the
native water; this can cause large differences in pH or redox condition
* The native water or sediment do not possess a sufficient pH buffering capacity
(e.g., acidic waters)
* There is a large difference in elemental concentrations between the inj section and
the native water (e.g., fluoride) and significant mixing occurs
* A change in chemical condition of the water having contact with the sediment is
able to trigger maj or (e.g., dissolution of gypsum) or minor (e.g., dissolution of
heavy metals) reactions.
Herczeg et al. (2003), discuss the effects of inj section of storm water into a brackish
limestone aquifer over a Hyve-year period. Herczeg et al. also note that the major effect
was observed at a monitoring well located 25 meters from the ASR well. Significant
carbonate dissolution (35+/-6 grams of CaCO3 dissolved per cubic meter of aquifer) and
sulfide mineral oxidation was recorded. Less than 0.005% of the total aquifer carbonate
matrix was dissolved during each inj section event, and approximately 0.2% of the total
reduced sulfur. In addition, measurements of dissolved inorganic carbon values show
that substantial aqueous CO2 WAS produced by oxidation of organic matter associated
with the inj ected water.
AR or ASR wells may also be subj ect to corrosion. Corrosion can lead to reduced
well efficiency and poor recovered water quality. According to ASCE (2001), corrosion
should be a design concern in any of the following cases:
* Low pH acidic water
* DO in water
* Hydrogen sulfide in water
* High TDS (over 500 mg/1)
* Carbon dioxide in excess of 50 mg/1
* Chloride ions in excess of 300 mg/1
* High temp of water in well
Corrosion problems have been reported at one notable proj ect in Texas at the
Hueco Bolson AR site in El Paso (Bureau of Reclamation, 1996c). Injection wells have
had plugging problems due to improper well development and corrosion. Redevelopment
has to occur once every 3 to 4 weeks. Iron, manganese, and zinc compounds have
clogged the galvanized steel well screen. The inj section wells are subj ect to
electrochemical corrosion. The owners have evaluated several options to alleviate the
corrosion problem including applying cathodic protection to the inj section wells.
Mitigation measures available include corrosion resistant steel, non-metallic casings,
greater steel wall thickness (sacrificial), coatings on casing, or cathodic protection
systems (ASCE, 2001).
The final general ASR performance category is related to operational considerations
of each site. Many operational features are in the purview of the site owner. For
instance, the level of water treatment specified controls the quality of the injected source
water. Source water containing large amounts of total suspended solids (TSS) or total
organic carbon (TOC) can clog injection wells over time (ASCE, 2001). Well clogging is
a serious ASR performance issue that must be considered carefully.
Johnson (1981) reported the principal causes of clogging in an inj section well to be:
* Gas binding or air entrainment
* TSS in inj section water
* Bacterial contamination of aquifer or filter pack by bacteria growth
* Chemical reactions between recharge and ambient groundwater
* Ion-exchange reactions that could result in clay particle dispersal/swelling
* Precipitation of iron in the inj section water as a result of aeration
* Biological changes in the inj section water and the groundwater
* Swelling of clay colloids in the dewatered portion of the aquifer
* Mechanical j amming of the aquifer materials caused by particle rearrangement
when direction of water movement through the well and aquifer are reversed
Vecchioli and Ku (1972) observed maj or problems with well clogging during a
Hield AR trial in Long Island, New York. In one test, specific capacity was reduced by
half after 10 days of inj section. Vecchioli and Ku noted that the Magothy Aquifer (AR
storage zone) had a Eine gradation and is sensitive to TSS in influent water.
Redevelopment activities resulted in restoration of most of the specific capacity. Usually,
the first slug of recovered water from redevelopment activities was very turbid with high
concentrations of iron, phosphate, and volatile solids. Vecchioli and Ku also observed
that the bacterial content was high in the recovered water indicating some biological
clogging in addition to physical clogging by TSS.
Fitzpatrick (1986) noted similar problems at an ASR site in Lee County, Florida.
Tests using varying concentrations of influent source water showed severe clogging from
TSS and biological growth. Head buildup reached 200 feet in one test. Back flushing
helped alleviate this problem. Recovered water contained no coliforms or fecal
streptococcus, however, growth of anaerobic bacteria was noted and were determined
through observed water quality changes (increases) in ammonia and iron. Decreases in
dissolved organic carbon, organic N, and nitrate also occurred.
Bichara (1986) completed extensive laboratory testing on well clogging using
different media types and source water with variable TSS concentrations. In general,
finer-grained media were the most sensitive to physical clogging by well inj section.
Moncaster (2004) provides detailed evaluations of well clogging and efficiency
issues for the Portland, Oregon Columbia South Shore well field. Moncaster is still
investigating clogging issues in large capacity ASR wells at the Portland location but has
attributed some of the problems to the total mass of suspended solids inj ected rather than
just the concentration of TSS in the injected source water.
Inj section volume is another performance variable under the control of the owner;
larger inj section volumes will likely increase the site performance as noted previously in
this report. The site infrastructure including the well, pumps and piping, are all
controlled through design efforts instituted by the site owner. Proper well design may
reduce potential for air entrainment (Pyne, 1995; Groundwater Solutions, 2004). The
owner may also be able to elicit some control over the timing of recharge. Source water
from lakes or reservoirs may contain high algae counts that can clog inj section wells
(Bureau of Reclamation 1994; Bureau of Reclamation, 1996b). Temperature of the
source water may affect ASR system performance. Since hydraulic conductivity of the
ASR storage zone is a function of density and viscosity, adjustments to the "apparent
transmissivity" need to be made to account for lower temperature recharge water (Reeder
et al., 1976; Fitzpatrick, 1986; Hickey, 1989; Castro, 1995; Groundwater Solutions,
2004). Lower apparent transmissivity values can lead to higher recorded well pressures
during inj section operations.
Brackish water ASR sites
The performance of a brackish water ASR system is controlled by complex
interactions among many variables. The performance of an ASR system has been
explored through examination of existing site data (Harpaz and Bear, 1964; Harpaz,
1971; Reeder et al. 1976; Brown and Silvey, 1977; Pyne, 1998; Miller et al. 1998; Reese,
2002), development of physical models (Kimbler et al., 1975), through development of
simple analytical models (Esmail, 1966; Esmail and Kimbler, 1967; Moulder, 1970;
Kimbler et al. 1975; USACE, 1979), and through development of numerical models
(Khanal, 1980; Merritt et al. 1983; Merritt, 1985; Merritt, 1986; Yobbi, 1996; Merritt,
1997; Huntley and Bottcher, 1997; Gaus et al., 2000; Wright and Barker, 2001; Missimer
et al. 2002; Pavelic et al. 2002; USACE and SFWMD, 2004).
ASR researchers in the 1960s (Harpaz and Bear, 1964; Esmail, 1966; Esmail and
Kimbler, 1967; Harpaz, 1971) conducted numerous field tests and examined the
theoretical basis for storing "freshwater" within saline aquifers. These researchers
demonstrated that a number of performance factors were important for storing freshwater
within saline aquifers. Among these factors were dispersive mixing, regional
groundwater gradient, density gradient, and aquifer material. Harpaz and Bear (1964)
noted that long term storage of water in a dolomite aquifer was unsuccessful due to pre-
existing groundwater gradient that caused the inj ected water to translate down gradient
where it could not be recovered. Esmail (1966) introduced the idea of a "density
gradient" between the freshwater lens and the ambient saline water within the storage
aquifer. He also suggests that a mixing zone resulting from dispersion and diffusion
would retard the effect of gravitational segregation, with a smaller rate of "interface
laydown" or buoyancy stratification. Harpaz (1971) noted that recovery of freshwater
was lower in limestone aquifers as compared to sandstone aquifers.
ASR researchers in the 1970s (Moulder, 1970; Harpaz, 1971; Kimbler et al. 1975;
Reeder et al. 1976; Brown and Silvey, 1977; USACE, 1979) were focused upon obtaining
results from large-scale field trials and on improving the theoretical understanding of AR.
Although the term ASR had not been coined quite yet, the AR field trials in Texas
(Moulder, 1970), Minnesota (Reeder et al. 1976), and Virginia (Brown and Silvey, 1977)
all provided valuable information on recharge and possible recovery of stored water.
Kimbler et al. (1975) provides a detailed evaluation of storing freshwater in saline
aquifers. Both analytical and physical modeling was performed. As part of the
theoretical development, Kimbler et al. assumed that:
* Aquifer is horizontal, homogeneous, and isotropic, and is of infinite areal extent.
* Viscosities of inj ected and native fluids are the same
Based upon both analytical solutions and physical modeling using "mini-aquifers",
Kimbler et al. developed a good understanding of some of the key factors in ASR
performance in saline aquifers. Kimbler noted the following important factors:
* Molecular diffusion and convective dispersion
* Segregation of two fluids due to density differences
* Pre-existing groundwater gradient
* Aquifer dip
* Aquifer storage zone thickness
Kimbler also discusses the recovery of the inj ected freshwater defining a term
called "recovery efficiency" (RE). This is the percentage of the volume of freshwater
recovered versus the volume injected. Kimbler uses recovery efficiency to examine
performance of individual cycles of inj section and recovery. Kimbler concludes that RE
increases in every cycle if storage times are short and recovery does not remove the entire
injected residual. For multiple cycles, he uses the term "cumulative recovery efficiency"
(CRE) to account for unrecoverable water that forms a residual in the aquifer. Using the
physical models developed for the study, Kimbler et al. determined that thinner storage
zones result in higher RE values than comparable thick storage zones. RE of dipping
aquifers (greater than 30 degrees) is generally less than comparable horizontal aquifers.
Lastly, Kimbler et al. note that the higher the density differential between the inj ected
water and the ambient saline groundwater, the poorer the RE performance. The same is
true for a high degree of mixing or high pre-existing gradient.
Reeder et al. (1976) describes a case study in Minnesota where over two million
seven hundred thousand gallons of highly treated wastewater were inj ected into a
solution-riddled dolomite storage zone. During the recharge event the temperature of the
recharge water dropped from 15 to 11.2 degrees Celsius; a concomitant drop in recharge
rate was noticed at the same time (rate dropped from 108 to 90 gallons per minute). In
addition, it was noted that although the recharge water contained concentrations of total
dissolved solids (TDS) in excess of 3 mg/1, no significant well clogging was reported.
Lastly, the mixing of the recharged wastewater was characterized as moderate to high due
to aquifer dispersion. Dispersivity of the dolomite zone was determined from a single
well tracer test to be approximately 280 feet.
Brown and Silvey (1977) provide a thorough study of AR and recovery of the
recharge water at a site in Norfolk, Virginia. The Norfolk field trial was hampered by
dispersion of interstitial clay particles contained within the heterogeneous aquifer storage
zone. If not for the clay dispersion issues, the Norfolk field trial would have been a
highly successful example of freshwater storage within a slightly saline aquifer. The
authors estimated that after a few cycles, up to 85% of the recharged water could be
recovered prior to exceeding regulatory limits for chloride in drinking water. The
predicted performance was attributed to the ambient aquifer water quality (only slightly
brackish) and the low amount of mixing observed in the sandy portions of the aquifer.
ASR researchers in the 1980s (Khanal, 1980; Merritt et al. 1983; Merritt, 1985;
Merritt, 1986) were focused upon obtaining results from extensive numerical modeling
Khanal (1980) utilizes a digital model, based upon analytical work completed by
Kimbler et al. (1975), to examine controls upon RE performance for ASR wells located
in saline aquifer environments. The objectives of the study were:
(1) to predict recovery efficiency of the cyclic storage/retrieval system via
(2) to perform sensitivity analyses of the model parameters in order to predict the
effect of changing these.
Khanal examines RE based upon data from an existing St. Lucie County, Florida
ASR well. Khanal examines the effect of multiple variables upon RE. He reviews the
effect of density differential, aquifer storage zone thickness, aquifer transmissivity, and
dispersivity. His findings agree with Kimbler et al. (1975) for the most part. Large
density differences between recharged water and ambient saline groundwater (e.g.
freshwater versus seawater) lead to poor RE while thin storage zones result in better RE
values. High transmissivity values also revealed poor performance with RE declining as
transmissivity values increased. Studies of dispersivity were not at the proper scale and
the results are deemed inconclusive. Further evaluations determined that the RE value
typically declined with long storage times prior to recovery of the inj ected water. RE
values were halved when storage time of 2 years was simulated compared to 180 days of
storage. Although it is not discussed in detail within the report, the assigned aquifer
gradient is most likely responsible for the observed decrease in RE with higher values of
storage time. As was noted by Harpaz and Bear (1964), pre-existing gradients within the
aquifer tend to cause the inj ected freshwater to translate down gradient where portions of
it become unrecoverable.
Merritt et al. (1983) discusses results from three field trials conducted in Florida.
First, a field trial conducted at the Cocoa Beach water plant near Orlando, Florida, is
discussed. Table 2-1 provides key trial data:
Table 2-1. Data from Cocoa Beach ASR field trial
Cycle 1 2 3 4 5
Volume In 11.2 11 11.6 33 28.5
Storage 1 1 1 1 1
Volume out 3.8 5.7 7.7 14.4 21.4
RE (%) 33.9 51.8 66.4 43.5 75.1
Qin (m) 700 700 675 740 665
Qout (p) 915 955 985 970 970
The Cocoa Beach trial took place from 1969 to 1970 and five full cycles of recharge
and recovery were completed. The storage zone was within the Floridan Aquifer System
and consisted of sandy limestone with an open hole interval of approximately 205 feet.
The bottom Hyve feet of the storage zone was identified as "cavernous". These data
clearly shows that RE does improve over time if the storage interval duration is short.
Merritt et al. (1983) also discusses tests in Pinellas County, Florida by Black, Crow,
and Eidsness, Inc., 1974. The storage zone was 40 feet thick and contained ocean water.
Initial test cycles used short duration storage times (practically zero) so RE was 43% to
46%. The third test cycle utilized a 10 hour storage period resulting in a reduced RE of
39%. Fifth and Sixth cycles with storage periods of at least 16 hours resulted in RE of
1% for each cycle. The poor performance was attributed to buoyancy stratifieation that
happened in the storage zone due to ineffective geologic confinement. Based upon the
Hield results, the authors speculated that very high hydrodynamic dispersion occurred in
the Karst-like dolomitic zones located throughout the storage zone.
Merritt et al. (1983) also summarizes work by Wedderburn and Knapp (1983) that
was completed at an ASR test site near Jupiter, Florida in 1975 to 1976. The initial cycle
test resulted in RE of approximately zero but increased to 35% by cycle 4. Due to the
low salinity (chloride concentrations of 2,000 mg/1) value in the aquifer storage zone, the
authors speculate that an appreciable degree of buoyancy stratifieation did not occur. A
storage period of 120 days during cycle 4 did not cause a large reduction in RE as was
seen in the Pinellas County, Florida site.
The report also observes that RE can be reduced if changes occur in the vertical or
lateral distribution of permeability due to plugging of the formation around the well
during inj section. This phenomenon may result in unrecoverable water becoming trapped
in the aquifer storage zone. Lastly, the report explains that phenomena such as (1) degree
of uniform flow, (2) degree of anisotropy in the aquifer and (3) degree of hydrodynamic
dispersion are all highly dependent upon the structure of the aquifer material.
Merritt (1985, 1986) used a numerical prototype model to evaluate ASR
performance factors. Merritt focuses his efforts on the various factors affecting ASR
recovery efficiency (RE). The prototype model was assigned radial hydraulic
conductivity (Kh) values ranging from 0.18 to 520 feet per day and vertical hydraulic
conductivity (Kv) values ranging from 0.10 to 40 feet per day. Model runs to test
buoyancy stratification effects at the initial values utilized (ambient chloride
concentration = 2,000 mg/1), revealed that significant buoyancy stratification did not
occur and recoverability was not affected. Significant effect was noticed when Kh and
Kv were multiplied by at least a factor of 10. When seawater concentrations and
densities were simulated in the aquifer (TDS =35,000 mg/1), more significant buoyancy
stratification was demonstrated. RE was reduced in half as compared to the original Kh
and Kv values. When Kh was multiplied by 5 times, the RE was reduced to 9 % from an
original value of 67 %. In a test with Kh equal to 10,000 feet per day and Kv equal to 10
feet per day, RE was estimated to be 26.7%. Merritt also evaluated the effect of aquifer
storage zone thickness upon RE. Merritt's findings echo earlier researchers in that
thinner storage zones generally result in better RE performance. Model simulations
revealed that RE ranged from 67.5% at thickness of 10 feet to 61% at 50 feet.
Merritt also reviewed the effect of aquifer anisotrophy upon RE. The simulations
produced mixed results when comparing isotropic and anisotropic aquifers. At higher
dispersivity values, RE was almost equal under either case. At low dispersivity values,
RE was lower in anisotropic aquifers. Merritt also concludes that the degree of
hydrodynamic dispersion is one of the main controls on ASR performance in saline or
brackish water aquifers. Using model simulations with an ambient chloride concentration
of 2,000 mg/1 and density equal to 62.57 pounds per cubic foot, the RE varied from 28%
for moderate dispersion using a dispersivity value of 30 feet to an RE value 74% for a
case of low dispersion using a dispersivity value of 2 feet. Merritt (1985) noted that RE
was somewhat sensitive to porosity changes and observed that increasing porosity from
20% to 50% led to reduction of RE (from 24% to 14%) for higher dispersivity values
with only minor reductions of RE at low dispersivities (from 71% to 64%). In later
studies, Merritt (1986) concludes that RE is not sensitive to changes in porosity as long as
the values are in a reasonable range (e.g., 30 to 50%).
In the case where recovery of freshwater occurs immediately after inj section, RE
values were unchanged when including a realistic regional gradient as part of the
simulation (e.g., a gradient similar to observed values within the FAS in Florida). When
storage periods intervened, RE values dropped. Based upon results of numerous
simulations, Merritt demonstrates that the effects of storage time were minor at 6 months
but significant at 5 years. Initial RE was 60.9% using 2,000 mg/1 of chloride in the
ambient groundwater storage zone. After 6 months of ASR storage RE was 59.9%, a
slight reduction from the zero storage simulation. After 5 years, RE was reduced to
21.9% due to pre-existing gradient applied in the numerical model.
In his later research efforts, Merritt found that unequal inj section or extraction rates
did not affect RE. Wells that were not fully penetrating showed very minor changes in
RE with reductions of up to 1%, as compared to fully penetrating wells. Merritt did
confirm that volume inj ected was strongly related to RE. Higher Volumes lead to better
RE up to an asymptotic limit. Merritt (1986) provides a Eigure compiling simulation
results for different initial inj section volumes. At an inj section volume of approximately
six million cubic feet of freshwater, the improvements become very small and an
asymptote is observed. Similar to other researcher Eindings, Merritt also shows that RE
improves with successive cycles as long as the cycles stop recovery at 250 mg/1
Chloride.4 For the simulation case with a low dispersivity value of two to four feet with
no interlayer dispersion, RE reached a maximum with an asymptote after four to five
cycles. At higher dispersivities (e.g., 30 feet), 8 to 10 cycles were required to reach the
maximum asymptote. Figure 2-3 depicts the simulation results from Merritt (1986)
along with data from the USGS Cocoa Beach ASR trial from 1970. Note that both the
simulations and the real Hield data show that the RE improves from cycle to cycle as long
as the storage period is short. The Eigure also indicates that the number of cycles required
to reach a maximum asymptote increases as the dispersivity decreases.
ASR researchers in the 1990s (Yobbi, 1996; Merritt, 1997; Huntley and Bottcher,
1997) were focused upon obtaining results from extensive numerical modeling
Yobbi utilized the finite-element model, HST3D, to evaluate the importance of
various parameters on the recovery of effluent in a saline aquifer (Yobbi, 1996). Yobbi
performed model simulations based upon earlier work presented by Hickey and Ehrlich
4 Regulatory limit for drinking water under the Safe Drinking Water Act
0 1 2 3 4 5 6 7
# of ASR Cycles -W- Cocoa Beach (USGS, 1970)
-1Alpha=20ft (Merritt, 1986)
-eAlpha=20ft (Merritt, 1986)
Figure 2-3. Results from historical reports by Merritt et al. (1983) and Merritt (1986)
The y-axis is RE percentage and the x-axis is ASR cycle number.
As the research is compiled and reviewed, similar conclusions are drawn by many
of the key investigators. Like earlier researchers, Yobbi determined the following:
* The greater the density difference between the inj ected effluent and ambient
groundwater, the lower the recovery efficiency
* Higher groundwater salinity makes density stratification more likely
* Recovery efficiency decreases markedly as dispersivity increases
* Generally, high formation permeability causes poor recovery efficiencies
* Partial inj section well aquifer penetration as compared to complete aquifer
penetration has an insignificant effect on recovery efficiency
* Porosity and anisotropy variations do not significantly alter recovery efficiencies
Merritt (1997) provides additional discussion of ASR recovery efficiency in
brackish water aquifers. Merritt develops a prototype model of the Hialeah ASR site near
Miami, Florida. He constructed a three dimensional model representing the
heterogeneous and anisotropic aquifer found at the Hialeah location. The model
simulates ASR performance within the FAS in south Florida. Most of the work is similar
to his previous efforts discussed above. However, Merritt does mention the potential for
interlayer dispersion in real aquifer systems and how some existing models are not able to
accurately simulate this phenomenon. Generally, interlayer dispersion can reduce ASR
RE in some cases.
Huntley and Bottcher (1997) developed numerical simulations of a highly layered
aquifer system and found reductions in estimated RE as compared to isotropic
homogeneous cases. Layered aquifer systems are probably more common than
homogeneous systems due to geologic processes such as sedimentation.
ASR researchers in the present decade (Gaus et al. 2000; Wright and Barker, 2001;
Missimer et al. 2002; Pavelic et al. 2002; USACE and SFWMD, 2004) were focused
upon obtaining results from extensive numerical modeling simulations.
Gaus et al. (2000) describes the progress made in developing models simulating
both the physical and geochemical aspects of ASR schemes. SWIFT is a fully transient
3-D model that simulates flow and transport of fluids. It is ideally suited to modeling
ASR and has been used to simulate the response of the four maj or aquifers in the UK -
Chalk, Lincolnshire Limestone, Sherwood Sandstone, and Lower Greensand. The
aquifers encompass dual-porosity, fractured, and porous-media aquifers.
Sensitivity analyses of the model's responses to matrix porosity, fracture porosity,
fracture permeability and thickness were carried out during the investigation. Results
showed low sensitivity to parameters in the estimated ranges with only matrix porosity
having a significant effect in the Chalk, the Lincolnshire Limestone and the Sherwood
Sandstone. The most important conclusion from the evaluation of ASR performance is
that dual-porosity aquifers will need more conditioning than single porosity aquifers.
Wright and Barker (2001) studied the dual-porosity Chalk aquifer in England using
a semi-analytical model. The study noted the importance of characterizing the aquifer
thoroughly in order to more accurately evaluate potential ASR performance.
Missimer et al. (2002) discusses success or failure of ASR systems based upon local
hydrogeology. Predominant factors discussed are aquifer hydraulic properties and
density contrast between the water in the storage zone and the inj ected water. The article
if the hydraulic properties are not compatible with the ASR concept being
designed, then the system will likely fail regardless of the inj section and recovery
rate. (Missimer et al. 2002, p. 33)
Most ASR systems that have achieved a high RE occur in slightly brackish-water
aquifers or in aquifers with a high degree of confinement. Missimer et al. (2002) reveal
that the selection of the right portion of the aquifer storage zone is a key component to a
successful project. Based upon model results completed using SEAWAT (Guo and
Langevin, 2002), Missimer et al. evaluated potential operational scenarios for the
proposed Everglades ASR project (USACE and SFWMD, 1999). The study noted that
while 80% RE could be achieved within five years in moderately brackish storage zones
(4,000 to 5,000 mg/1 TDS), an economical RE could not be reached in 25 years for
storage zones containing seawater. The maj or conclusion was that the ASR proj ect
would fail under these circumstances because of the density differences.
Missimer et al. also evaluated highly permeable storage zones with moderately
brackish ambient groundwater and determined that the ASR system would also fail or
have extremely low RE values. The authors recommend an aquifer transmissivity
ranging from 6,700 ft2/day to 47,000 ft2/day and ambient groundwater with a TDS value
of less than 20,000 mg/1. Due to possible density stratifieation, the aquifer should also be
well confined on top of the storage zone with some basal confinement below the storage
zone. Missimer also studied the effects of large-scale anisotropy. It was noted that
anisotropy greatly influences the distribution of inj ected water and possibly "channels"
the stored water in certain areas where the water may become unrecoverable. In stratified
sedimentary rocks, there is a disparity between the hydraulic conductivity in the
horizontal plane versus the vertical plane. Common ratios of horizontal hydraulic
conductivity to vertical hydraulic conductivity range from 5 to 100. Stratifieation plays
an important role in defining the geometry of subsurface inj ected freshwater. As the
stratifieation of the aquifer becomes more pronounced, buoyancy stratification of the
injected freshwater becomes less severe. In cases where formation stratifieation or
vertical anisotropy is negligible, buoyancy stratification of inj ected freshwater can be
quite problematic due to density differentials. Due to buoyancy stratification, injected
freshwater moves upward to form a cone-shaped plume. While in the anisotropic aquifer,
the upward movement of inj ected water is restricted, so that a ball-shaped plume or
bubble is formed. Inj ected freshwater can also follow preferential flow pathways creating
poor RE due to "fingering flow" where dense water sinks into freshwater that has been
Pavelic et al. (2002) used a combination of numerical model simulations and
dimensionless parameters to measure the effectiveness of various contrived ASR
systems. Pavelic et al. identified the two key performance factors that affect ASR RE,
namely dispersion associated with aquifer heterogeneity and displacement of inj ected
freshwater due to regional groundwater flow. As part of the study, Pavelic et al. devised
two simple dimensionless lumped parameters to evaluate each of the two key ASR
performance factors. The dimensions of the inj ected water plume may be estimated by
determining the radius of an idealized cylinder of water within the aquifer storage zone.
This idealized radius assumes that no dispersion takes place during the inj section period.
Therefore, this value termed rm by Pavelic et al. can represent an advective plume of
water. The amount of dispersion is generally controlled by the intrinsic dispersivity (u).
Pavelic et al. proposed using these two terms in a ratio to create a dimensionless
parameter termed "relative dispersivity". The relative dispersivity is a ratio of
dispersivity to rm or a/rm. As this dimensionless ratio gets larger, ASR RE decreases
since the amount of dispersion grows larger compared to the advection. Pavelic et al. also
propose a second ratio called the "relative drift" which is the ratio of the effective
displacement of the inj ected water (due to pre-existing gradient) to rm. Pavelic et al. use
the proposed performance ratios in combination with numerical modeling to determine
some additional ASR performance considerations. First, similar to other researchers,
larger inj section volumes can lead to higher values of RE. Second, storage times greater
than 100 days combined with higher regional gradients tend to reduce the RE. As
dispersion increases, RE decreases.
The USACE and SFWMD (2004) performed numerical modeling of proposed ASR
proj ects in south Florida. The modeling determined that RE is also sensitive to the
regulatory regime. For instance, for a potable ASR proj ect, under Federal drinking water
standards, recovery of freshwater could continue until the chloride concentration
exceeded 250 mg/1, while for an environmental ASR proj ect, under State of Florida
surface water regulations, recovery duration is governed by the concentration of specific
conductance. Through model simulations, the USACE and SFWMD found that at the
Hillsboro ASR pilot proj ect site, RE would be better if the recovered water was proposed
for use for potable purposes as compared with its intended use for environmental users.
This finding is significant and reinforces the concept of optimal ASR well site selection.
For brackish water ASR sites, performance metrics are generally lacking. For ASR
proj ects utilized in support of irrigation, additional parameters of interest would be
sodium, boron, and herbicides. For ASR projects supporting environmental in-stream
uses, critical parameters of interest are unknown at this time. It is easy to see that
recovery efficiency by itself is not a sufficient performance metric since it is highly
dependent on the use and regulation of the recovered water.
Review of Other ASR Site Selection Factors
Typically, ASR sites are also located to maximize their effectiveness and minimize
potential environmental impacts. Various site selection factors may be important
including location of:
* Existing groundwater users
* Important habitat
* Reliable power
* Available source water
* Customers or water users
* Suitable hydrogeology
Collection of Existing ASR Site Data
The formulation of an improved planning methodology for ASR proj ects should be
based upon results and "lessons learned" at existing operating proj ects. With that theme
in mind, the author undertook a large data collection effort for this research report. First,
existing published data were collected and collated. Published ASR data ranged from a
brief proj ect summary to extensive reports. Some published data were available for a
total of 30 sites. In addition to the published data, the author contacted numerous ASR
owners and developers across the USA, Australia and England to request key ASR
operating data. A total of 20 ASR proj ect sites were contacted and agreed to send data.
The data sent by the ASR proponents varied in importance and scale as well as format
(e.g., hard copies vs. electronic data deliverables). A net sum of 50 sites is discussed
herein and located on Figure 2-4.
Seattle, WA ASR Project Data
Salem, OR Huron. SD en1'
Beaverton, OF rra en, L- _re 'l N
Salt Lake afl"
City, UT MQ
Washoe SDb- l~l e WI MI \~ RI
County, NV ..* .
-- kirtli PEich SC
Highlands Rslch -I' Hilt.n Hwel.::'C
Denver Soulrb *
International S~ites Y 1P Floridia Sites ...'''::'j Beach
LytchettMmn~res Englan)r '.'illls~I A~u trrald Fl '0- ..,.1 .p.'
Andrews Farm, Australia Northern India Peace River Springtree Mvan~atee Rd Lee Co N.
Clayton, Australia Hialea Detmay Beach Marco Lakes
Boynton Eastemn Hillsbooro Miami-Dade
Figure 2-4. Location of ASR proj ect sites where data were collected for this report.
The available data were organized into several categories. First, basic site
background information was gleaned from the datasets. Relevant basic site data consists
of the site location, geologic environment, and ambient groundwater quality (brackish
water vs. freshwater). For approximately one third to one half of the ASR proj ect sites,
operational data included influent level of total suspended solids (TSS), degree of well
clogging observed, extent of disinfection by-products recorded at the site, extent of
geochemical issues, and total cost per 1,000 gallons to develop the water supply. The
various data collected from each of the 50 sites was then compared and contrasted.
Lastly, key findings regarding the 50 sites were developed with an emphasis towards
improving operation at future proj ects such as the Everglades ASR program (USACE and
SFWMD, 2004). For this research effort, brackish water ASR sites have been segregated
from non-brackish water sites since each is significantly different.
Non-brackish water ASR sites
The non-brackish water ASR sites reviewed for this report include sites across the
United States, England, and Namibia. They represent diverse geologic environments as
well as different operating types. Twenty sites were reviewed for this effort. Available
data ranged from extensive reporting for Oak Creek and Green Bay, Wisconsin to short
summaries available for the Huron, South Dakota site. Electronic data were provided for
a number of sites also. This data facilitated development of unit water costs. Figure 2-5
shows the location of the non-brackish water ASR sites utilized in this report.
A brief synopsis of each site is provided in this report to aid with the development
of an ASR planning decision framework. The brief summary will detail basic site
information (if available) along with a discussion of special issues or "lessons learned"
from the site. These sites were also selected due to the wealth of data available for each
one in the literature. In addition, for several of the sites, the author secured additional
reports and data that have not been widely published. Generally, more data were
available for these sites than were readily available for the brackish-water proj ect sites.
For that reason, discussions of some of the brackish-water sites available later on in this
report are abbreviated.
ASR Project Data
Seattle, WA. NOn-brackish Water Sites
Salern, OR Huron, SD C
Beaverton, CI ,-,
Salt Lake MTlLB ( 7
City, UT M
Washoe c k "ISD e WI
County, NV W
Las Vegas,: 1Q Cw
Highlands Rlll nc b 0 :
Denver Sowh -.
Figure 2-5. Location of non-brackish water ASR proj ect sites where data were collected
for this report.
Seattle ASR project. The Seattle, Washington ASR site, also referred to as the
Highline well field site, is located immediately south of the city downtown. The Highline
well field was designed to provide supplemental water supply to the city, augmenting the
supply from Lake Youngs, a reservoir located southeast of the city. Groundwater
modeling of the system revealed that peak demand pumpage of 6 to 8 MGD would result
in significant long-term groundwater declines (Bureau of Reclamation, 1994). A solution
to this problem was to utilize ASR technology to provide aquifer recharge when excess
surface water was available. The ASR system was constructed and tested in 1991. Full-
scale single-well and multi-well testing was performed from 1991 to 1993.
The well system is screened in unconsolidated glacial deposits characterized as
highly permeable sand, gravel, and cobbles. The aquifer system has an average
transmissivity of 3,000 ft2/day and is a confined to semi-confined aquifer.
Water quality in both the aquifer and source water was deemed to be acceptable
with minor amounts of radon, manganese, iron, and zinc present. Total suspended solids
of the treated source water ranged from 1.0 to 4.0 mg/1. Recharge operations were
delayed twice during the proj ect due to flooding impacts in late 1990 (e.g., associated
highly turbid source water) and in 1992 due to drought conditions that affected source
water flows and permissible diversions. In addition, during summer months, excessive
algae growth in Lake Youngs resulted in moderate clogging of the ASR well. This
clogging was found to be reversible through periodic back flushing or well re-
development. During recovery operations, minor amounts of disinfection by-products
(total trihalomethanes) were observed but at concentrations well below regulatory levels.
Minor geochemical enrichment of manganese, iron, and radon was also noted during
ASR recovery operations. Radon levels frequently exceeded proposed regulatory
standards at that time (e.g., greater than 300 pCi/L). Site engineers noted that aeration of
the water could remove the radon from the recovered water if water blending was not
possible. Recovery of the injected water was highly successful during pilot testing
operations. After several cycles the recovery efficiency approached 100%. Geotechnical
problems resulting from ASR operation were explored at the site but found to be
minimal. Subsidence of overlying clay confining units was not deemed a problem due to
past geologic history and pre-consolidation from the weight of glacial ice. The Seattle
Water Department completed a thorough cost analysis of the proj ect and determined that
the overall unit cost was approximately $0.54 per 1,000 gallons recovered. This unit cost
was significantly less than the cost of other water supply options considered. One lesson
learned from the site was that algae growth in the source water may be problematic and
lead to well clogging. Removal of the algae prior to ASR recharge would alleviate this
Portland ASR site. The City of Portland Bureau of Water Works operates the
largest municipal water supply in Oregon, serving approximately 840,000 people
(Portland Bureau of Water Works, 2001). The primary source of water for the system is
the Bull Run watershed located east of the city. The current system has an average day
demand of 1 15 MGD with short-term peaks as high as 200 MGD. The City of Portland
also relies upon the Columbia South Shore Well Field (CSSW) for backup water supply
or supplemental summer supply when peak season demand requires it (Portland Bureau
of Water Works, 2001). During the 1990s, the region grew steadily and its reliance upon
the CSSW increased. A regional water supply plan included several ASR projects as
components and the City of Portland decided to test the concept of ASR at its existing
The ASR system is located at the CSSW and consists of four wells screened within
the Portland area "Sand-and-Gravel Aquifer (SGA)". The SGA is a highly permeable
alluvial aquifer composed of medium to coarse sand and gravel. It has an average
transmissivity of 2,700 ft2/day and storage coefficient of 2 x 10-4 as determined from
aquifer performance tests. The aquifer is a confined aquifer in the study area. Four
additional wells screened within the Troutdale Sandstone are also under consideration.
Water quality of the source water and ambient groundwater were deemed of acceptable
quality. The source water from the Bull Run system is an unfiltered surface water
supply, one of the few such systems remaining in the United States. The source water is
disinfected with chlorine at the headworks, and later ammonia and sodium hydroxide are
added to maintain a disinfectant residual and for corrosion control (Golder and
Associates, 2003). TSS of the recharge water generally ranged from 1.0 to 1.67 mg/1,
however, maintenance operations may have introduced highly turbid water into the well
system in June 2002 (Golder and Associates, 2003). During recovery operations, minor
amounts of disinfection by-products (total trihalomethanes) were observed but at
concentrations well below regulatory levels. Minor geochemical enrichment of calcite
and magnesium was also noted during ASR recovery operations resulting in a small
increase in water hardness. In addition, during long-term testing of all four ASR wells,
excessive sand generation was noted by the site operator. This was later determined to be
due to lack of a pressure relief valve on the well or a faulty packer within the well.
Dissolved oxygen levels were usually higher during initial recovery operations than
during extended recovery. This may be due to biological growth within the wells.
Recovery of inj ected water approached 100% and provided a high-quality water supply.
Geotechnical problems resulting from ASR operation were explored at the site but found
to be minimal. Subsidence of overlying clay confining units was not deemed a problem
due to past geologic history and pre-consolidation from the weight of glacial ice. The
author completed a thorough cost analysis of the proj ect and determined that the overall
unit cost was approximately $0.29 per 1,000 gallons recovered. This unit cost was
significantly less than the cost of other water supply options considered by the City of
Portland. One lesson learned from the site was that well clogging problems can
materialize at any site if the source water TSS is high or if the TSS is low but the mass
injected is high (Moncaster, 2004). Well clogging at the CSSW has resulted in a 5 to
37% reduction in well efficiency for the proj ect. Periodic well re-development can help
improve this situation but only if begun at the early-stages of a proj ect.
Beaverton ASR site. The City of Beaverton ASR Project is located south of
Portland, Oregon at the City's Sorrento Water Works (Groundwater Solutions, Inc.,
2004). The proj ect receives its water from the Joint Water Commission. The Joint Water
Commission's treatment plant is located near Forest Grove, Oregon and receives its water
from the Trask and Tualatin Rivers (Eaton, 2004). The ASR system consists of two wells
that store water in the basalt aquifer during winter and spring months when river flows
are high. The stored water is recovered in the summer and fall months to help meet peak
system demands. The wells are also available during emergency situations such as
extreme weather or flooding of the primary water supply. As of February 2004, six
recharge and recovery cycles have been completed. During 2002 to 2003, 394.6 million
gallons of treated drinking water were stored in the basalt aquifer by the ASR system.
The ASR wells are screened (open-hole interval) within the Columbia River Basalt
Group (Eaton, 2004). The aquifer is highly fractured and behaves as a confined to semi-
confined aquifer with average transmissivity of 13,369 ft2/day and a storage coefficient of
1 x 10-4. Water quality of the source water and the ambient groundwater is deemed
acceptable. The source water is chlorinated at the treatment plant and usually contains
TSS of approximately 10 mg/1. During recovery operations, minor amounts of
disinfection by-products (total trihalomethanes) were observed but at concentrations well
below regulatory levels. One interesting observation is that the concentration of total
haloacetic acids (HAAs) was reduced to non-detectable levels during storage while the
total trihalomethanes were reduced based upon mixing patterns of other compounds. It is
possible that biodegradation of the HAAs did occur at the Beaverton ASR site. No
significant geochemical reactions have been observed at the site, only simple mixing and
hydrodynamic dispersion effects. Radon concentrations of the recovered water
sometimes exceed the regulatory limit similar to the ambient groundwater supply.
Aeration of the recovered water could remove this as an issue. No pathogens were
observed in recovered water although minor occurrences of total coliform were noted in
the source water. Dissolved oxygen levels were usually higher during initial recovery
operations than during extended recovery. This may be due to biological growth within
the wells caused via recharge of oxygen rich water. Recovery of inj ected water
approached 100% and provided a high-quality water supply.
The City of Beaverton completed a thorough cost analysis of the proj ect and
determined that the overall unit cost was approximately $1.99 per 1,000 gallons
recovered. This unit cost was significantly less than the cost of other water supply
options considered (Eaton, 2004).
There are many lessons learned from this ASR project site. First, during recharge
events high water levels were noted in the aquifer. The high water levels were partly
attributed to increased flow in an area seep. In an urbanized environment, seeps can be
problematic due to perceived flooding risks. Monitoring of existing seeps before and
during recharge events can aid in the interpretation of the seep flows. Second, the static
water level of the basalt aquifer is typically 200 feet below land surface, and without a
down hole control valve, air entrainment can be problematic at the site. Third, lining old
well boreholes can reduce turbulence during inj section and reduce head loss during
injection and recovery. Lastly, periodic back flushing of the wells is critical to
maintaining efficient ASR well operations and reducing well clogging.
Salem ASR site. The City of Salem ASR project is located in Oregon in the
southern Salem Heights area of the city (Golder Associates, 1995). Salem is in the
northern end of the Willamette Valley between the Cascade and Coastal range of
mountains. Salem is the state capital and home to approximately 140,000 residents. This
population is expected to rise dramatically over the next decade and approach 228,000 by
2013 (Butts, 2002). Traditionally, most water supply in the area is provided through
allocation of treated surface water from the Santiam River. This supply has been very
reliable, however, severe flooding in 1996 caused the treatment sand filter plant to be
shut down for several days (Butts, 2002). The flooding event and other circumstances
have led city engineers to question the long-term viability of the existing water supply.
Alternate water supply systems may be more dependable in emergency situations and
could be located closer to demands than the current system. Due to these issues, the City
of Salem is exploring ASR as a water supply option for emergency supplies and
supplemental water for use during peak demand periods.
Pilot testing began in 1995 and included a significant data collection program. Pilot
testing included long term pumping tests and a 30-day inj section day where 3 8,3 15,700
gallons of treated water were inj ected into the ASR well. The ASR test well is drilled to
316 feet below land surface and includes a 12-inch diameter steel casing with an open-
hole interval of 36 feet. The ASR wells are screened (open-hole interval) within the
Columbia River Basalt Group (Golder Associates, 1995). The aquifer is highly fractured
and behaves as a confined to semi-confined aquifer with average transmissivity of 32,000
ft2/day and a storage coefficient of 2 x 10-3. The aquifer is believed to have formed when
molten lava flowed into a marshy depression or shallow lake. The contact of the lava and
the water caused the lava to quench very rapidly causing extensive fracturing of the basalt
rock (Golder Associates, 1996a). The rock surrounding the study area is postulated to
have cooled over a long period of time, thus forming considerably less fractures in the
basalt. This surrounding rock forms a natural barrier to groundwater flow and provides
an excellent underground storage zone (Golder Associates, 1996a). Additionally,
geologic faulting in the area may provide an additional barrier to groundwater flow.
Water quality of the source water and the ambient groundwater is deemed
acceptable and is very similar (Golder Associates, 1996b). The source water is filtered
through slow sand fi1ters and disinfected with chlorine. It usually contains TSS
concentrations of approximately 0.3 mg/1 or less. The source water does contain minor
amounts of total coliform and fecal coliform as well as low concentrations of disinfection
by-products including THMs and HAAs (EPA, 1999b). Average concentrations of
TTHMs and THAAs were 35 ug/1 and 26 ug/1, respectively (Golder Associates, 1996c).
During the 60-day storage operations prior to ASR recovery, minor amounts of a few
disinfection by-products including chloroform and bromodichloromethane were observed
but at concentrations well below regulatory levels. No significant geochemical reactions
have been observed at the site, although extensive geochemical modeling did predict
possible precipitation of ferrihydrite compounds (Golder Associates, 1996b), known to
cause well screen encrustation (Johnson, 1981). The modeling also concluded that only
simple mixing and hydrodynamic dispersion effects would predominate the final
chemistry of the mixed waters. Radon concentrations of the recovered water sometimes
exceed the regulatory limit similar to the ambient groundwater supply. Aeration of the
recovered water could remove this as an issue. No pathogens were observed in recovered
water although minor occurrences of total coliform were noted in the source water.
Bacterial "standard plate count" levels were usually higher during initial recovery
operations than during extended recovery. This may be due to biological growth within
the wells. Recovery of inj ected water approached 100% and provided a high-quality
Several interesting items were noted based upon a review of the Salem ASR
reports. First, although the aquifer is quite transmissive and the inj section water TSS is
extremely low, minor well clogging was observed at the ASR well. Well efficiencies
declined from 98% to 86% after 30 days of inj section at 1.3 MGD. Clogging was
attributed to the TSS and possible air entrainment of the aquifer. Second, geotechnical
evaluations were completed at the site to evaluate the possibility of vertical hydraulic
"j acking" or hydrofracturing. It was recommended that the allowable head increase be
limited to 200 feet of buildup to minimize j acking effects (Golder Associates, 1996b).
Salt Lake City ASR site. The southeast Salt Lake County ASR proj ect is one of
13 demonstration proj ects implemented by the Bureau of Reclamation (BOR) under the
"High Plains States Groundwater Demonstration Program Act of 1983". The proj ect was
cost-shared between the BOR and the Salt Lake County Water Conservancy District
(SLCWCD) starting in 1990. EPA and USGS provided technical assistance and
interpretation of the data. The proj ect is located in a highly urbanized
residential/commercial area in Salt Lake County, about 8 miles SE of Salt Lake City,
Utah (Bureau of Reclamation, 1996b).
The proj ect was developed to test the feasibility of providing needed additional
capacity for delivery of municipal water by storing treated drinking water underground
during the winter for withdrawal during the peak summer demand season. The project, if
found feasible, would be expanded in lieu of enlarging water conveyance facilities or
building additional costly surface storage. Injection wells were selected for use since
spreading basins were not practical in the urbanized area. Source water was available
from Bureau of Reclamation' s Deer Creek Reservoir in Provo Canyon, UT via the Provo
River and then the 34-mile long Salt Lake Aqueduct. The water is then conveyed to the
Little Cottonwood Water Treatment Plant.
The geological environment is an unconfined aquifer composed of cobbles, sands,
and silts deposited as colluvium. The site location takes advantage of high transmissivity
values determined to be approximately 4,947 ft2/day at the project site. Natural recharge
to the aquifer is derived from Wasatch Front precipitation (primarily snowmelt)
percolating through fractured bedrock into the unconfined aquifer nearby. The
groundwater quality is excellent.
The proj ect consists of one inj section well, one recovery well, one dual-purpose
well, three monitoring wells, and an inline filtration plant with dual-media pressure filters
and UV disinfection. Other existing wells may also be utilized for recovery and
monitoring. Recovered water is distributed through existing mains owned by SLCWCD.
The inj ected water meets all required regulatory standards under the UIC program. The
source water is chlorinated at the main treatment plant and usually contains TSS of
approximately 1.0 mg/1 or less. During recovery operations, minor amounts of
disinfection by-products (total trihalomethanes) were observed but at concentrations well
below regulatory levels.
Well plugging problems were mainly attributed to small suspended particles that
passed through the dual media filters. In addition, residues from water treatment
coagulation chemicals may precipitate in the aquifer. Plugging at one inj section well
created an additional 30 feet of head loss. Calculations suggest that up to 10% of the
specific capacity is lost over the inj section period. Redevelopment activities included
mound collapse, wire brushing the well casings, swab surging, and pump surging. Pump
surging was found to be the most effective method. One-hour redevelopment cycles
were required to return most of the inj section well capacity. Redevelopment resulted in
substantial unanticipated costs.
The Bureau of Reclamation and City of Salt Lake completed a thorough cost
analysis of the proj ect and determined that the overall unit cost was approximately $0.09
per 1,000 gallons recovered. This unit cost was significantly less than the cost of other
water supply options considered (Bureau of Reclamation, 1996b).
One important lesson learned at this site was that during the project, SLCWCD met
with greater than expected legal and institutional demands due to debates concerning
water rights. One conclusion was that the State Water Engineer did not have existing
state laws to address artificial groundwater recharge projects. Regulatory agencies did
not know how to address the proj ect causing the use of significant staff time from the
sponsor and regulators. In addition, local zoning laws made the acquisition of proj ect
sites time consuming.
Huron AR site. The Huron artificial recharge and recovery proj ect is one of 13
demonstration proj ects implemented by the Bureau of Reclamation (BOR) under the
"High Plains States Groundwater Demonstration Program Act of 1983". The proj ect was
cost-shared between the BOR and the South Dakota State University starting in 1990
(Bureau of Reclamation, 1996d).
Multiple droughts have been recorded within the James River Basin in eastern
South Dakota over the last 20 years. These droughts forced local irrigation users to
utilize the local glacial aquifers heavily causing persistent water declines within the
aquifer system. In addition to the existing irrigation wells in the study area, the City of
Huron, South Dakota owns a municipal well field in the area that is used for backup
water supply when low flows are present within the James River. The well field is
mostly used during late winter if the James River is frozen or in late summer or early fall
when river flows are low. The City of Huron anticipates continuing demand for the
limited water supplies available. This problem was seen as an opportunity to evaluate
artificial recharge in this area to test the overall recharge potential for the buried glacial
sediments (Bureau of Reclamation, 1996d).
The concept plan developed was to use high flows from the James River during
high spring flow events, treat the source water in the City of Huron' s water treatment
plant, pipe the water to the well field, and then inj ect the water into the Warren aquifer, a
buried glacial aquifer in the study area. A portion of the inj ected water was later
recovered for water supply purposes (Bureau of Reclamation, 1996d).