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Quantifying the Near-Borehole Geochemical Response during Aquifer Storage and Recovery

Permanent Link: http://ufdc.ufl.edu/UFE0021312/00001

Material Information

Title: Quantifying the Near-Borehole Geochemical Response during Aquifer Storage and Recovery Application of 'Push-Pull' Analytical Techniques to ASR Cycle Testing
Physical Description: 1 online resource (58 p.)
Language: english
Creator: Norton, Stuart Bryan
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2007

Subjects

Subjects / Keywords: aqueous, aquifer, arsenic, asr, chemistry, ferric, geochemistry, hydrogeology, hydroxide, limestone, mobilization, oxidation, pyrite, recovery, reduction, storage, suwannee, swfwmd
Environmental Engineering Sciences -- Dissertations, Academic -- UF
Genre: Environmental Engineering Sciences thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Arsenic mobilization has become the primary regulatory issue for aquifer storage and recovery (ASR), posing a significant problem to the long-term viability of this alternative water supply technology. We compared the current conceptual model for arsenic mobilization in ASR with results from field tests (i.e., cycle tests) completed at an ASR facility in southwest Florida that uses the Suwannee Limestone for aquifer storage. We developed a framework for conducting field-scale tests, based on single-well Push-Pull Test analytical methods, to determine first-order reaction rates for dissolved oxygen (DO), the primary oxidant, in ASR. The measured DO decay rates from four test cycles ranged from 0.41/day to 0.72/day and were shown to be temperature dependent. The methods presented herein potentially extend the application of the Push-Pull Test to quantify the near-borehole geochemical response during ASR. To confirm the appropriateness of the historical ASR operational approach (i.e., target storage volume) for managing ASR recovery efficiency and attenuating arsenic, field results from ASR cycle tests and results from the 3-D Interactive Groundwater (IGW) Model calibrated to the case site were evaluated. The findings of this research indicate that the TSV approach can be used to increase ASR recovery efficiency but is not a viable means of attenuating arsenic.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Stuart Bryan Norton.
Thesis: Thesis (M.S.)--University of Florida, 2007.
Local: Adviser: Annable, Michael D.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2008-08-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2007
System ID: UFE0021312:00001

Permanent Link: http://ufdc.ufl.edu/UFE0021312/00001

Material Information

Title: Quantifying the Near-Borehole Geochemical Response during Aquifer Storage and Recovery Application of 'Push-Pull' Analytical Techniques to ASR Cycle Testing
Physical Description: 1 online resource (58 p.)
Language: english
Creator: Norton, Stuart Bryan
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2007

Subjects

Subjects / Keywords: aqueous, aquifer, arsenic, asr, chemistry, ferric, geochemistry, hydrogeology, hydroxide, limestone, mobilization, oxidation, pyrite, recovery, reduction, storage, suwannee, swfwmd
Environmental Engineering Sciences -- Dissertations, Academic -- UF
Genre: Environmental Engineering Sciences thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Arsenic mobilization has become the primary regulatory issue for aquifer storage and recovery (ASR), posing a significant problem to the long-term viability of this alternative water supply technology. We compared the current conceptual model for arsenic mobilization in ASR with results from field tests (i.e., cycle tests) completed at an ASR facility in southwest Florida that uses the Suwannee Limestone for aquifer storage. We developed a framework for conducting field-scale tests, based on single-well Push-Pull Test analytical methods, to determine first-order reaction rates for dissolved oxygen (DO), the primary oxidant, in ASR. The measured DO decay rates from four test cycles ranged from 0.41/day to 0.72/day and were shown to be temperature dependent. The methods presented herein potentially extend the application of the Push-Pull Test to quantify the near-borehole geochemical response during ASR. To confirm the appropriateness of the historical ASR operational approach (i.e., target storage volume) for managing ASR recovery efficiency and attenuating arsenic, field results from ASR cycle tests and results from the 3-D Interactive Groundwater (IGW) Model calibrated to the case site were evaluated. The findings of this research indicate that the TSV approach can be used to increase ASR recovery efficiency but is not a viable means of attenuating arsenic.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Stuart Bryan Norton.
Thesis: Thesis (M.S.)--University of Florida, 2007.
Local: Adviser: Annable, Michael D.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2008-08-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2007
System ID: UFE0021312:00001


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1 QUANTIFYING THE NEAR-BOREHOLE GE OCHEMICAL RESPONSE DURING AQUIFER STORAGE AND RECOVERY: APPLICATION OF PUSH-PULL ANALYTICAL TECHNIQUES TO ASR CYCLE TESTING By STUART BRYAN NORTON A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2007

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2 2007 Stuart Bryan Norton

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3 To my loving wife. Thank you for allowing me to pursue my academic interests. Your commitment to this research and self sacrifice can not be overstated.

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4 ACKNOWLEDGMENTS I thank my supervisory committee (Drs. Mike Annable, Kirk Hatfield, Jean-Claude Bonzongo, and Mark Newman) for their guidance a nd support. I thank the City of Bradenton, specifically Seth Kohn and Claude Tankersley, for al lowing me to use their site as a case study. I also thank Jones Edmunds & Associates, Inc. for allowing me to use the companys resources. This research was funded by the Florida Ge ological Survey, with a partial matching contribution by the University of Florida Wate r Resources Research Center through the USGS Water Resources Research Act Program. Im gratef ul to Dr. Jon Arthur of the FGS for providing both financial support and technical input and to the WRRC for its contribution. My scholarly interests have long been nurture d by my mother. I thank her for many years of loving guidance, encouragement, and patience. This research would not have been possible without the commitment of these individuals.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................4 LIST OF TABLES................................................................................................................. ..........6 LIST OF FIGURES................................................................................................................ .........7 LIST OF SYMBOLS AND ABBREVIATIONS............................................................................8 ABSTRACT....................................................................................................................... ............10 CHAPTER 1 INTRODUCTION..................................................................................................................11 2 BACKGROUND....................................................................................................................15 Mobilization of Metals During ASR......................................................................................15 Occurrence of Arsenic-Bearing Mine rals in the Suwannee Limestone..................................16 Principles of Arsenic Mobility................................................................................................17 Geochemical Models............................................................................................................. .17 Conceptual Model............................................................................................................... ....19 3 METHODS........................................................................................................................ .....23 Site Selection................................................................................................................. .........23 Site Hydrogeology.............................................................................................................. ....24 Bradenton Cycle Test Program...............................................................................................26 Bradenton Sampling Program.................................................................................................27 Push-Pull Tests................................................................................................................ .......27 Interactive Groundwater Model..............................................................................................31 4 RESULTS........................................................................................................................ .......38 Water Chemistry................................................................................................................ .....38 Cycle Test Results............................................................................................................. .....39 PPT Results.................................................................................................................... .........41 IGW Model Results.............................................................................................................. ..44 5 CONCLUSIONS....................................................................................................................53 LIST OF REFERENCES............................................................................................................. ..55 BIOGRAPHICAL SKETCH.........................................................................................................58

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6 LIST OF TABLES Table page 3-1 Well construction details for the Bradenton HSPS ASR facility.......................................37 3-2 Bradenton ASR cycle test program summary....................................................................37 4-1 Bradenton ASR water quality summary............................................................................52

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7 LIST OF FIGURES Figure page 2-1 The Eh-pH diagram for arsenic at standard conditions.....................................................20 2-2 Pyrite oxidation dur ing aquifer recharge...........................................................................21 2-3 Reductive dissolution of arsenic during recovery..............................................................22 3-1 Site location map.......................................................................................................... ......34 3-2 Site plan.................................................................................................................. ...........35 3-3 Generalized geologic profile..............................................................................................36 3-4 Model details and input parameters...................................................................................36 4-1 Field parameters measured during Cycle Tests 1-4...........................................................46 4-2 Analytical parameters reported for Cycle Tests 1-4..........................................................46 4-3 Field parameters measured during Cycle Tests 5 and 6....................................................47 4-4 Analytical parameters repor ted for Cycle Tests 5 and 6....................................................47 4-5 Analytical parameters reported for Cycle Test 6a.............................................................48 4-6 Plot of ln(C*r(t)/C*tr(t)) versus t* fo r Bradenton ASR Cycles Tests 1, 2, 5, and 6..........48 4-7 vant Hoff Plot of Bradenton ASR cycle test data.............................................................49 4-8 PPT breakthrough curve for Bradenton ASR....................................................................49 4-9 IGW model calibration results for TDS measured at SZMW-1........................................50 4-10 IGW model calibration results for TDS measured at ASR-1a...........................................50 4-11 IGW model calibration results for TDS measured at AFMW-1........................................51 4-12 IGW model calibration re sults for water levels.................................................................51 4-13 Simulated results for full-scale operations at the Bradenton ASR facility........................52

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8 LIST OF SYMBOLS AND ABBREVIATIONS AFMW-1 Arcadia Monitoring Well No. 1 As arsenic ASR Aquifer Storage and Recovery ASR-1 Aquifer Storage and Recovery Well No. 1 AsS2arsenic sulfide bls below land surface Cr concentration of reactant Ctr concentration of tracer DO dissolved oxygen FAC Florida Administrative Code FDEP Florida Department of Environmental Protection HFOs ferric hydrox/oxyhydroxides HMOs metal hydrox/oxyhydroxides HPD hierarchical patch dynamics HSPS High Service Pump Station H2S hydrogen sulfide IGW Interactive Groundwater Model k reaction rate coefficient MG million gallons mg/kg milligram per kilogram mg/L milligram per liter msl mean sea level NELAC National Environmental Labor atory Accreditation Conference ORP oxidation reduction potential

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9 PDWS Primary Drinking Water Standards PPT Push-Pull Test PVC polyvinyl chloride SDWS Secondary Dri nking Water Standards SOPs standard operating procedures SZMW-1 Storage Zone Monitoring Well No. 1 TDS total dissolved solids TMR telescopic mesh refinement TSV target storage volume UFA Upper Floridan Aquifer g/L microgram per liter UIC Underground Injection Control USDW Underground Source of Drinking Water Vext extracted volume Vinj injected volume WTMW-1 Water Table Monitoring Well No. 1 WTP water treatment plant YSI Yellow Springs Instrument Company Hr molar enthalpy of reaction

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10 Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science QUANTIFYING THE NEAR-BOREHOLE GE OCHEMICAL RESPONSE DURING AQUIFER STORAGE AND RECOVERY: APPLICATION OF PUSH-PULL ANALYTICAL TECHNIQUES TO ASR CYCLE TESTING By Stuart Bryan Norton August 2007 Chair: Michael Annable Major: Environmental Engineering Sciences Arsenic mobilization has become the primar y regulatory issue for Aquifer Storage and Recovery (ASR), posing a significant problem to th e long-term viability of this alternative water supply technology. We compared the current conceptual model for arsenic mobilization in ASR with results from field tests (i.e., Cycle Tests) co mpleted at an ASR facility in southwest Florida that uses the Suwannee Limestone for aquifer storage. We developed a framework for conducting field-scale tests, based on singlewell Push-Pull Test analytical methods, to determine first-order reaction rates for dissolv ed oxygen (DO), the primary oxidant, in ASR. The measured DO decay rates from four test cycles ranged from 0.41/day to 0.72/day and were shown to be temperature dependent. The met hods presented herein po tentially extend the application of the Push-Pull Test to quantify the near-borehole geochemical response during ASR. To confirm the appropriateness of the hi storical ASR operational approach (i.e., Target Storage Volume) for managing ASR recovery efficiency and attenu ating arsenic, field results from ASR cycle tests and results from the 3D Interactive Groundwater (IGW) Model calibrated to the case site were evaluated. The findings of this research indicate that the TSV approach can be used to increase ASR recovery efficiency but is not a viable means of attenuating arsenic.

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11 CHAPTER 1 INTRODUCTION With an annual average rainfall of 54-inches (1), Floridas climate produces much of the water needed to support its grow ing population. However, most of the rainfall occurs during the rainy (wet) season, typically May through September. In south Florida, over 70 percent of the annual rainfall occurs during the we t season (2). Much of the exce ss wet season flow is lost to evaporation or to streams where it is discharged to the ocean. Because the capacity of aboveground storage reservoirs is limited, little of the excess flow is placed in storage. In contrast to the summer months, Floridas springtime is usually dry, with rainfall of a tenth of an inch or more falling fewer than six days in April (2). Springtime in Florida is also the height of the growing season, when many residents increase resident ial lawn irrigation to combat the lack of precipitation. Because the dry season occurs when the demand for water is greatest and when surface reservoirs are experiencing low water levels, significant stresses are placed on groundwater resources. The temporal dispropor tion of water supply to demand not only creates seasonal supply shortfalls, but also contributes to groundwat er quality declines in one of the most prolific aquifers in the world, the Floridan aquifer. Floridas Water Management Di stricts are the primary regulat ory agencies responsible for managing the water resources of the State. Because of the histor ical overproduction of groundwater resources across peninsular Florida, the Water Management Districts have been enacting strict measures that lim it groundwater withdrawals (3). In fact, the Southwest Florida Water Management District, the South Florida Water Management District, and the St. Johns River Water Management District have recently established the Centra l-Florida Coordination Area covering central and east-central Florida in cluding parts of Brevard and Lake Counties and all of Polk, Osceola, Orange, and Seminole Countie s. This interagency agreement established

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12 that no additional withdrawals from the Upper Floridan Aquifer (UFA) may occur beyond those permitted through 2013, despite an anticipated increase in potable water demands in the area (3). To continue to meet the demands of a growing population in the face of this new restriction, alternative water supply technolog ies such as Aquifer Storage and Recovery (ASR) must be developed (4). Artificial recharge techniques such as ASR ha ve the potential to al leviate seasonal water supply shortfalls for many communities. In Flor ida, ASR is typically employed to meet seasonal supply shortfalls by storing excess water in nonpotable (brackish) aq uifers during the wet season, when demand is low, and recovering th e stored water during the dry season, when demand is high. ASR facilities in Florida typi cally use a single well for both injection and recovery of the stored water. As with other water supply technologies, su ch as surface water re servoirs or reverse osmosis, ASR has technical challenges that must be addressed. Each ASR facility is held to a stringent set of water quality regulations set forth in the Florida Administrative Code (FAC), as administered by the Florida Department of Environmental Protection (FDEP) Underground Injection Control (UIC) program (5). These re gulations require that, for injection into an Underground Source of Drinking Water (USDW), defined in FA C Ch. 62-520.410 as an aquifer with a background total dissolved solids (TDS) c oncentration of less than 10,000 mg/L (6), the injectate must meet the Primary and Seconda ry Drinking Water Standards (PDWS & SDWS) within FAC Ch. 62-550 (7). FDEP applies this rule to both the recharge water (injectate) and the water recovered in ASR. This implies that the injectate can neither introduce a contaminant into the aquifer nor produce a respons e that releases a contaminant from the aquifer matrix. However, the injectate may be allowed to ex ceed some of the SDWS (e.g., color, odor, TDS)

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13 providing that the concentration of the SDWS in the injectate is lower than that of the background concentration of the aquifer. To demonstrate compliance with the regulations FDEP requires that full-scale operational tests (Cycle Tests) be conducted at each facility before the faci lity is placed into operation. Cycle Tests are designed and permitted on a site-sp ecific basis, generally reflecting the intended operational approach of the ASR facility. To simulate ASR operational practices, Cycle Tests typically include a large-volume recharge (injection) phase, a s hort or long-term storage phase, and a recovery (pumping) phase. Cycle Tests, wh ile conducted on a much larger scale in terms of recharge and recovery volumes, are similar in design to Istoks Push-Pull Test method (8). Therefore, the approach presented here uses exis ting Push-Pull Test (PPT) analytical methods for ASR Cycle Test data analysis. PPT analytical methods are discu ssed in greater detail in the Methods section of this thesis. ASR facilities in southwest Florida have re cently reported arsenic concentrations in recovered water at levels greater than 112 g/L (9). The elevat ed arsenic concentrations are likely due to a geochemical response that mobilizes native arsenic and other trace metals during aquifer recharge (9, 10). Sin ce the PDWS for arsenic was lowere d from 50 g/L to 10 g/L (Ch. 62-550 F.A.C., Table 1) in January 2006 (7), ar senic mobilization above the PDWS has become the primary regulatory concern for ASR facilities. In the past, the FDEP has allowed continued operation of ASR facilities as long as the PDWS for arsenic was not exceeded at the property boundary closest to the ASR well. Therefore, the historical operational approach for Floridian ASR facilities was focused on meeting the arsenic standard at the closest pr operty boundary and maintaining a high recovery efficiency for the facility. Typically this was accomplished by recharging the aquifer with large

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14 volumes of water during the initial ASR cycles, while only recovering a sm all percentage of the stored water. This approach, termed the Tar get Storage Volume (TSV), leaves large volumes of injected water in the formation, allowing for a buffer zone or transition zone between the native (brackish) groundwater and the recharge wate r. By allowing for the loss of recharge water during the initial ASR cycles, the recovery effici ency of subsequent cycles may approach the designed capacity of the facility (11). It ha s been proposed that, by allowing for a transition zone between redox zones of native groundwater and recharge water, the TSV approach may also attenuate arsenic within the formation (11). With this approach, th e recharge and recovery volumes of the facility are limited so that ar senic will not exceed the PDWS at the nearest property boundary during aquifer recharge or at the ASR well during recovery. Recently the FDEP has adopted a strict posi tion on arsenic in ASR by prohibiting any exceedance of arsenic above the 10 g/L standard, either at the ASR borehole or onto adjacent properties (12). According to FD EP, compliance with the arsenic standard must be met at all times and at all points within the aquifer. Therefore, arsenic concentrations may not exceed the standard in onsite monitoring wells, nor can the standard be exceeded in water recovered from the ASR well (12). ASR facilities will now be required to demonstrate compliance with the arsenic standard by reco vering the full volume of the inject ed water during ope rational testing (i.e., Cycle Testing). Due to the changing regulatory position on arseni c, changes in the operational approach for Florida ASR facilities must be considered. To a ddress these issues, this thesis will 1) compare the current conceptual model for arsenic mobiliz ation in ASR with results from Cycle Tests conducted at the Bradenton ASR facility, 2) pres ent a framework for conducting field-scale tests based on Push-Pull Test analytical methods to quantify the near-borehol e geochemical response

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15 that occurs during ASR, 3) compare Bradenton ASR Cycle Test results with numerical modeling results using the 3-D Interactive Groundwater (IGW) Model calibrated to the Bradenton ASR Site, and 4) evaluate the a ppropriateness of the TSV appro ach for managing ASR recovery efficiency and attenuating arsenic. CHAPTER 2 BACKGROUND Mobilization of Metals During ASR The first occurrence of arsenic in Florida AS R sites was reported by the Florida Geological Survey (FGS) while conducting re search funded by FDEP (9, 10, 13) This research included a detailed mineralogical and geochemical review of ASR facilities in southwest Florida including the NW Hillsborough County Reclaimed ASR faci lity, the Rome Avenue ASR facility (Hillsborough County), the Punta Gorda ASR fac ility (Charlotte County), the Peace River ASR facility (DeSoto County) and others, all of wh ich use the Suwannee Limestone as the storage zone for ASR. Elevated concentrations of uranium, arsenic, manga nese, nickel, vanadium, molybdenum, and other metals were detected in water recovered from these sites. Because the concentrations of these metals were low in bot h the injected water and native groundwater, and after ruling out anthropo genic sources, FGS concluded that the source of the metals is likely from dissolution of minerals (e.g., pyrite) within the aquifer matrix (9, 10). The injection of source water with high levels of oxidizers, such as DO, into a reduced aquifer releases (mobilizes) metals by mineral (e. g., pyrite) oxidation (9). Variables effecting the mobilization of metals during ASR include 1) the chemistry of the native and recharge waters, 2) the mineralogy of the aquifer matrix, 3) the amount of time the recharge wate r is in contact with

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16 the aquifer matrix along with th e number of operational or test cycles conducted, and 4) sitespecific hydrogeology and geoc hemistry (9, 10). Occurrence of Arsenic-Bearing Minerals in the Suwannee Limestone To identify the source of arsenic in ASR, Pri ce and Pichler (14) completed a mineralogical and geochemical analysis of more than 300 core samples collected from the Suwannee Limestone formation in southwest Florida. The re sults of this analysis indicate that arsenic was present within clean limestone (relatively pur e limestone without minor mineral phases) samples of the Suwannee Limestone at concen trations of around 1.7 mg/kg. Arsenic was reported at higher concentrations of 9.5 mg/kg in targe ted samples (samples containing visible trace minerals, minor constituents, or organic material). The targeted samples were selected because of the suspected associa tion of arsenic with trace minera l phases, such as pyrite, and organic material. Therefore, the resulting av erage arsenic concentration of 3.5 mg/kg reported by Price (14) for the bulk Suwannee Limestone may be skewed slightly as the calculated value included the concentrations from the targete d samples. However, the average arsenic concentration of 3.5 mg/kg is near the 2.6 mg/kg global averag e concentration for limestone reported by Smedley and Kinniburgh (15). The results of this st udy indicate that 1) the high arsenic concentrations present within the Suwannee Limestone are associated with pyrite minerals and 2) the bulk aquifer matrix cont ains relatively low leve ls of arsenic (14). Price and Pichler (14) concluded that mineral gr ains of pyrite are generally associated with high-porosity zones. Samples of pyrite were se lected from the cores and were analyzed for arsenic concentration. The results show that pyrite is generally ri ch in arsenic with an average arsenic concentration of 2300 mg/kg. This is within the arsenic concentration range for pyrite of 100 to 77000 mg/kg provided by Smedley and Kinnibur gh (15). Additionally, organic material

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17 and other trace minerals identified within core sa mples were analyzed and were not found to be a significant source of arsenic (14). Principles of Arsenic Mobility The speciation of arsenic is predominatel y controlled by the Redox potential (Eh) and by the pH of the system (15). However, it is unlikel y that differences in system pH play a dominant role in the dissolution of arsenic at ASR sites in Florida. SDWS require pH levels of 6.5 to 8.5 for recharge in ASR. Most municipal water s uppliers maintain slightly alkaline conditions (pH approximately 7.2 or greater) to prevent corrosion of distribution pipes. Th is is near the average background pH value of 7.3 0.4 measured in monitoring wells open to the Suwannee Limestone in southwest Florida (16). If we also neglect other geochemical, physical and biological (i.e., microbial) processe s, we can simplify the arsenic issue to focus on phase shifts, from the solid arsenic phase to the dissolved phase that result from cha nges in the redox (Eh) state of the system. The relationship between the oxida tion state of the system and the speciation of arsenic is shown in the Eh pH (Pourbaix) diagram (Figure 2-1). At a near neutra l pH, the solid arsenic species (As) is present at low Eh (reduced) cond itions of approximately -0.35 to -0.60 millivolts (mv). As the Eh increases from highly reduc ed conditions to more oxidized conditions (Eh values above -0.35 mv), arsenic (As) is dissolved to the arsenic-sulfide (AsS2 -) species (17). Geochemical Models Mirecki (18) used the geochemical model c ode PHREEQC-2 to simulate water quality changes during ASR test cycles at the Olga, North Reservoir, and Eastern Hillsboro potable water ASR systems. The study was conducted in support of the Comprehensive Everglades Restoration Plan (CERP). PHREEQC-2 is a computer program written in the C programming

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18 language and developed by USGS. The program is designed to perform a wide variety of lowtemperature aqueous geochemical calculations and is available for free download (19). The geochemical models employed by Mirecki ( 18) were used to simulate mixing during ASR recharge, geochemical reactio ns during storage and recovery, and the fate and transport of arsenic during ASR cycle testing as well as to investigate uncertainties in the model to identify additional data needed to support future modeling e fforts. Mirecki (18) s uggests that oxidizers in recharge water, primarily DO, di ssolve native pyrite minerals re leasing arsenic, iron, and other trace metals into solution. The iron re-preci pitates locally as ironoxyhydroxides (HFOs) during recharge, providing surface sites for the adsorpti on of arsenic. During recovery, the sorbed arsenic is re-released when native (i.e., sulfat e reducing) conditions re turn near the well, destroying the arsenic adsorption s ites (18). This suggests that HF Os act as an arsenic sink during recharge and as an arseni c source during recovery. Mirecki (18) concluded that 1) recharge mixing curves differ between the sites due primarily to hydraulic factors; 2) pyrite oxidation, HFOs precipi tation, and sulfate reduction and hydrogen sulfide (H2S) production occur in sequence during ASR cycle testing; 3) while ironoxyhydroxides (HFOs) can reduce the mobility of arsenic during ASR, the small masses of HFOs predicted in the models may not be sufficient to account for the high arsenic concentrations measured during recovery. A conceptual model of arsenic mobilization during ASR was also presented by Mirecki (18) and is expanded upon below. To demonstrate pyrite instability during ASR, Jo nes and Pichler (16) si mulated injection of treated surface water at three ASR sites in sout hwest Florida. Mixing of native water and ASR source water was modeled by the construction of Fe-S mineral stability diagrams. Stability fields were plotted for Fe-S mine rals in contact with various mi xing ratios of injection water to

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19 storage-zone water. Results indi cate that pyrite was stable under native gr oundwater (i.e., sulfate reducing) conditions and becomes less stable as the ratio of oxygenated water increased during injection. Variation in the pyrite st ability fields for the three sites was attributed to differences in native (i.e., background) groundwater sulfate concentrations (16). Unlike the results of geochemical modeling presented by Mirecki (18), the stability diagrams constructed by Jones and Pichler (1 6) suggest that HFOs are not stable under conditions found during ASR and, therefore, cannot be a source for adsorption of dissolved arsenic. However, the models developed by Jone s and Pichler (16) did no t consider water-rock interactions or the effects of other potential arsenic adsorbin g metal-oxides/hydroxides (HMOs) of aluminum, manganese, magnesium, molybd enum, or other trace metals. Given their abundance in aquifer materials, and because of their chemistry, oxides of aluminum, iron, and manganese are potentially the most important so urce and sink for arsenic in aquifer sediments (17). Conceptual Model The potential mechanisms by which arsenic is mobilized during ASR ha ve been identified. However, uncertainty remains regarding the mechan isms that control the fate and transport of mobile arsenic. Based on the conclusions of th e research completed to date (9, 10, 13-18), we can hypothesis a conceptual m odel for arsenic in ASR: The injection of water containing high levels of oxidizers (e.g., DO) into a strongly reducing (i.e., sulfate reducing) environment prod uces a geochemical response that solublizes native minerals (i.e., pyrite) releasing arsenic, ir on, and other trace metals into solution (Figure 2-2).

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20 The dissolved metals re-precipitate locally as metal-hydroxides (HMOs). Arsenic absorbs onto the freshly precipitated HMOs surface sites some distance farther away from the injection (i.e., ASR) well (Figure 2-2). During recovery of the stored water, native gr oundwater (i.e., sulfate reducing) conditions advance toward the ASR well. The reprecipit ated metals are solubilized under the reduced conditions, which destroys the HMOs adsorption sites and re-releases arsenic into solution (Figure 2-3). Figure 2-1. The Eh-pH diagram for arsenic at sta ndard conditions with total sulfur 10-3 mol/L and total arsenic 10-5 mol/L. Solid species are enclosed in parentheses in the crosshatched area (Welch et al. (17)).

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21 Recharge Low Permeability Unit Low Permeability Unit Low Eh (Reduced) H2S High Eh (Oxidized) Pyrite Oxidation Eh TransitionA s adsorption to HMOs Figure 2-2. Pyrite oxidation, leading to arsenic m obilization and formation of arsenic adsorption sites, during aquifer recharge

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22 Recovery Low Permeability Unit Low Eh (Reduced) H2S High As Destruction of HMOs Sites Low Permeability Unit Figure 2-3. Reductive dissolution of arsenic (m etal-hydroxide instabil ity) during recovery

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23 CHAPTER 3 METHODS Site Selection The City of Bradenton High Service Pump Station (HSPS) Potable Water ASR Facility (ASR-1) was used as the case study for this resear ch project. The site is located near downtown Bradenton in western Manatee County, Florida (F igure 3-1). Site sele ction was based on both the availability and comprehensiv eness of data sets collected dur ing seven test cycles conducted at the project site. Information presented in this study was obtained from the October 2006, City of Bradenton, Potable ASR Cycle Test Summary Report (20) and the February 2004, City of Bradenton, ASR Program, Phase II Well Construction Report (21). The City of Bradenton operates a conven tional surface water treatment plant (WTP) located at the Bill Evers Reservoir on Ward La ke (Figure 3-1). The lake was created in 1936 when the City constructed an 838-foot broad-cr ested weir impounding the Braden River. As the sole source of water for the City, the reserv oir was expanded in 1985 to meet the growing demands of the Citys p opulation (22). Water treated at the WTP is piped approximately 6 miles to the Citys High Service Pump Station (HSPS) site for storage and distribution to downtown Bradenton (Figure 3-1). In 2003 the City constructed an ASR facility (ASR-1) at the HSPS site as a way to store large volumes of water near the Citys populati on center to meet seasonal and emergency water supply shortfalls. Potable wate r is injected into ASR-1 eith er via high-service pumps or by gravity flow from onsite above-gr ound storage tanks. Water stored in ASR-1 is recovered via a single-vertical turbine pump. Du ring testing, recovered water is piped to waste in the Citys storm water collection system. Once the system is operational, the r ecovered water will be

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24 disinfected and piped either directly to the City s water distribution syst em or to storage in existing above-ground storage tanks. As shown in Figure 3-2, ASR facilities at the HSPS Site include an ASR well (ASR-1) with a single storage zone m onitoring well (SZMW-1) located 224 ft North of ASR-1. An intermediate aquifer monitoring well (AFMW-1) and a water table monitoring well (WTMW-1) are located 20.4 and 11.2 ft east of ASR-1, resp ectively. Well construction details, including screen or open-hole intervals, and casing size and elevations are provided in Table 3-1. Site Hydrogeology Peek (23) described the geologic formations of Manatee County to in clude surficial soil, sands, and limestone of recent to Pliestocene age of approximately 0 to 60 feet thickness. The surficial soils are underlain by Miocene-age se diments that make up the Hawthorn Group. The Hawthorn Group is an interlayered sequence of se diments that includes phosphatic clays, marl, sands, silts and limetones with an approximate th ickness of 150 to 360 feet (23). The Miocene age Tampa Member, of the Arcadia Formation, forms the base of the Hawthorn Group and is described by Peek (23) as a white, gray, and/ or tan, generally dense, hard, sandy, and partly phosphatic limestone with an approximat e thickness of 125 to 235 feet. The Oligocene age Suwannee Limestone is separated from the Hawthorn Group by sandyclay to clayey-sand confining unit (24). Th e Suwannee Limestone is described as a creamy white and tan, soft to hard, granular, porous, crys talline, and partly dolomitic limestone with a thickness of approximately 150 to 300 feet ( 23). The Suwannee Limestone is underlain by a thick (approximately 1700 to 2000 feet) sequence of carbonate rocks that includes the Eocene age Ocala Limestone, Avon Park Formation, Lake City Limestone, and Oldsmar Limestone (23). The sedimentary deposits described by Peek ( 23) form the multi-layered aquifer system present in the study area. Three aquifers the surficial aquife r, intermediate aquifer system, and

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25 Floridan aquifer are present (24). All deposits overlying the Ha wthorn Group make up the surficial aquifer. The surficia l aquifer is separated from the Hawthorn Group by a confining unit consisting of sandy-clay, clay, and marl. The Ha wthorn Group sediments form the intermediate aquifer system that contains up to three wate r-producing zones within the study area. The producing zones are separated by confining units and are composed primar ily of carbonate rocks (24). The Suwannee Limestone and Avon Park Formation are the two major water-producing zones within the Upper Florid an aquifer and are separate d by the less-permeable Ocala Limestone (24). A review of boring logs, geophys ical logs, and a video surv ey log completed during well construction indicates that the surficial aquifer is approximately 35 feet thick at the Bradenton HSPS site (21). The surficial aquifer consists of silty sand, of medium to coarse grains, with some shell present in the lower portion. Limest ones, clays, and siltstones of the Hawthorn Group are present at the site from appr oximately 35 to 295 feet bls. Gr ay to yellow, hard, fossiliferous limestone, likely the Tampa Member, is presen t from approximately 295 to 400 feet bls. Carbonates of the Upper Floridan aquifer unde rlay the Tampa Member with the Suwannee Limestone contact at approximate ly 400 feet bls. The Suwannee Limestone was described as a brownish-gray to yellowish-gray, partly micrit ic or crystalline, hard, limestone. Borings completed at ASR-1 and SZMW-1 were termin ated at approximately 550 feet bls (21). Therefore, the thickness of the Suwannee Limest one and depth to the Ocala Limestone contact were not determined. A generalized geologi c profile is included below (Figure 3-3). Both ASR-1 and SZMW-1 were initially drille d to approximately 550 feet bls. However, ASR-1 was grouted back to 505 feet bls due to the presence of a horizontal cavity of approximately -foot thick at 499.5 to 500 feet bls, as noted in the ASR-1 video survey log. The

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26 geophysical logs and video survey completed at ASR-1 indicate that the primary productive interval of ASR-1 is between 460 and 485 feet bl s with a few thin, approximately 2-inch-thick, porous intervals or solution features present. No other significant hi gh porosity zones were identified (21). Bradenton Cycle Test Program As with most ASR facilities in Florida, the testing program for the Bradenton ASR facility was designed to demonstrate compliance with FD EP regulations. To date, seven Cycle Tests (Cycles 1a) have been completed at the Br adenton ASR-1 site, in accordance with FDEP Permit Number 133098-027-UC. Testing began in November 2003 and was completed in June 2006 (20). The first series of tests (Cycles 1-4) we re conducted to measure the near-borehole geochemical response that occurs during ASR. Therefore, Cycles 1-3 were limited to 10-MG recharge events with approximately one week of storage and nearly complete recovery of the stored water. Test volumes for Cycle 4 were similar to the first three tests but the storage duration was extended to 29-days to allow the in jected water to further equilibrate with the aquifer. Cycles 5 and 6 were designed to test water quality changes as recharge water moves past SZMW-1 during build-out of the planned TSV of 160-MG. Cycle 5 included a 50-MG recharge event, with only 10-MG recovered, and was followed by Cycle 6 which included a 120-MG recharge event, with an additional 10-MG recove red. This design allowed for monitoring of the leading edge (i.e., the advec tive front) of recharge water as it moved past SZMW-1. Cycle 6a was initially designed to test the r ecovery efficiency of the ASR system at a limited recovery volume of 25-MG. However, gi ven the pending change in regulatory positions on arsenic, the recovery volume was increased to a total of 120 MG in order to determine the

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27 possible magnitude of arsenic concentrations at the nearest property boundary from ASR-1 (r = 75 ft). Additional details of the Cycle Test program are provided in Table 3-2. Bradenton Sampling Program Water quality data from Brad enton ASR facility were coll ected in accordance with the FDEP construction permit. While a more extens ive dataset was collected to support permitting, the parameters discussed in this thesis include analytical laboratory re sults for TDS, arsenic, magnesium, sulfate, and calcium and field data for temperature, DO, and oxidation reduction potential (ORP). As required by the construction permit, all groundwater samples were collected in accordance with FDEP Standard Operating Pr ocedures (SOP) 001/01 (20). Samples were collected by City staff and the Citys consulting Engineer in laboratory-supplied containers. Upon collection, the samples were immediately chilled (iced) to 4C and were shipped to an offsite laboratory for analysis. All laboratory anal yses, with the exception of the Citys in-house analysis for arsenic during Cycles 1-4, were performed by National Environmental Laboratory Accreditation Conference (NELAC) certified labs using FDEP-a pproved analytical methods. Field parameters were measured using a Ye llow Springs Instrument (YSI), Inc. 556 MPS instrument or YSI 6600-EDS datalogging sonde (20) All field instruments were calibrated and deployed in accordance with FDEP SOPs. Performance specifications for the field instruments can be found at www.ysi.com Push-Pull Tests Istok (8) and others (25-31) have used th e single-well Push-Pull Test (PPT) as an analytical tool for investigati ng contaminated sites and for remediation design and optimization. The PPT technique includes the injection (Push) of a tracer and/or re actant into an aquifer through a single well and, subsequentl y, the recovery (Pull) of the injectate from the same well.

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28 During the recovery phase, solute concentrations are measured to obtain breakthrough curves, to determine the amount of reactant (s) consumed and product(s) form ed, and to calculate reaction rates (8). The PPT method has been adapted to a variety of applications and site s. McGuire et al. (25) used this analytical met hod to evaluate the behavior of oxygen, nitrate and sulfate during aquifer recharge at a chlorinated solvent site. Kim et al. (26) evalua ted the in-situ aerobic cometabolism of ethylene, propylene, and c-DCE at a contaminated site using the PPT method. Leap and Kaplan (27) and Hall et al. (28) proposed a singlewell pump and drift test method similar to the PPT. These tests included a drift phase between recharge a nd recovery events that allowed for estimating local groundwater velocity and effective porosity. Scroth et al. (29) proposed methods for in situ ev aluation of solute sorption onto aquifer sediments using singlewell PPT methods. The approach detailed in this thesis was m odeled after the simplified method for estimating first-order reaction rate coefficients k (T-1) from Push-Pull Test data presented by Haggerty et al. (31). As described, simplified implies that the reaction rate estimat es are solely based on measured concentrations of tracer and reactant Estimates of the physical properties of the aquifer, such as hydraulic conductivity, disper sivity, or porosity, which are subject to uncertainty, are not required. The method proposed by Haggerty et al. (31) is based on the First-order decay equation rrdC kC dt (3.1) where Cr is the concentration of the reactant and t is time. Thus the decrease in the concentration of the reactant during time t is proportional to the decay rate and the concentration of the reactant.

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29 For a well-mixed reactor (assuming complete and instantaneous mixing of the injected solution within the aquifer) the relative concentra tion (i.e., the measured concentration C divided by Cinjection, respectively) of the reactant at any time t can be computed by **-kt rtrC(t) = C(t)e (3.2) where C*r is the relative concentration of reactant at time t, C*tr is the relative concentration of tracer at time t, and k[t-1] is the rate coefficient (32). A ssuming consumption of the reactant begins immediately upon injection (i.e., some of the reactant is be ing consumed during the finite length injection phase) the extr action phase breakthrough curve for a reactant is given by (*)(*) (*)injktt kt tr r injCt Ctee kt (3.3) where t* is the elapsed time since the end of the injection and tinj is the duration of the injection phase. Equation 3.3 can be re-written as *()1 lnln ()injkt r trinjCte kt Ctkt (3.4) Using a standard least square s routine, a plot of ln(Cr(t*)/Ctr(t*)) versus t* generates a straight line with slope equal to -k. and an intercept = ln((1 e-ktinj)/(ktinj)). For more details on the method development the reader is referred to Hagge rty et al. (31). This method was applied to the Bradenton Site to obtain First-order decay rates to investigate dissolved oxygen consumption during ASR. A non-linear l east squares regression was used to fit breakthrough data to equation 3.4. For our case Ctr(t*) is the relative Total Dissolved Solids (TDS) concentration and Cr(t*) is relative DO concentration. At Bradenton, background concentrations of the reactant (i.e., DO) were negligible. However, the background concentration of the tracer (i.e., TDS) was detectable at levels above 1100 mg/L, while

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30 concentrations of the injectate were gene rally less than 400 mg/L. Therefore, Ctr was calculated as a proportion between the injected TDS concen tration and the background concentration as *() ()bm tr o bmTDSTDSt C TDSTDSt (3.5) where TDSb is the measured background TDS concentration, TDSm(t*) is the measured TDS concentration at time t (i.e., time elapse d since end of the injection), and TDSm(to) is the measured TDS concentration at time t = 0 (i.e., end of the injection). This is similar to the approach presented by Maguire et al. (25). The major assumptions presented by Haggerty et al. (31) requires th at 1) both tracer and reactants exhibit identical retardation during trans port in the aquifer and 2) there be complete and instantaneous mixing of the inject ed test solution in the portion of the aquifer investigated by the test (i.e., the system behaves like a well mi xed reactor). To evaluate the second major assumption, Schroth and Istok (30) presented tw o alternative models to estimate First-order decay (k) rates that were based on different mixing assumptions including plug-flow and variably mixed reactor models. Using a semi-ana lytical solution to govern the solute transport equation, the authors performed sensitivity analys is on the three mixing models (i.e., well-mixed reactor, plug flow, and variably mixed reactor models) to comp are the accuracy of the obtained rate coefficients. Computations were perfor med for a homogenous, confined aquifer, with variable aquifer parameters and a heterogeneous, unconfined aquifer. For the well-mixed reactor model, Schroth and Istok (30) re ported less than 9% error for the confined homogenous aquifer case. The authors reported the largest errors fo r cases were the porosity (n) was low (estimated error = 5.1%), dispersivity ( L) was low (estimated error = 8.9%), and the injection time (tinj) was high (estimated error = 8.5%). For more details on the model sensitivity analysis, the reader is referred to Schroth and Istok (30).

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31 Interactive Groundwater Model To investigate solute transport during ASR, a 3-D model of the Bradenton site was developed using the Interactive Groundwater Model (IGW) version 4.7 (33). IGW is currently available for free download in 2-D and 3-D ve rsions. IGW presents a new approach to groundwater modeling were the user can view the gr aphic output of the model while the model is running, stop the computational process, edit the model input parameters, and re-run the simulation. Because post-processing of the mode l output isnt necessary, IGW allows the user to calibrate the model to site conditions as the m odel is being developed (i.e., refined) (33-35). To reduce computational time and provide real time visualization of the model out-put, IGW relies on hierarchical patch dynamics (H PD) (33). HPD allows modeling of complex systems across multiple-scales by coupling a sub-model( s) to a parent model. This approach is a generalization of the telescopic mesh refinement (TMR) technique as th e model uses a course grid (i.e., large grid size) over a large parent-mod el domain and a fine grid (i.e., small grid size) over a small sub-model(s) to increase the resolution of the model within the sub-model area(s) (33). A stable version of the 2-D model (Versi on 3.5.6 released on January 30, 2004) is available and includes a manual and tutorial wi th downloadable videos. However, the 3-D model is only currently available in a beta-versi on (Version 4.7 released on July 18, 2006) and therefore may not be completely stable on the us ers computer. A users manual for the 3-D was not available for download at the time of this stu dy. For more information on IGW, the reader is directed to the IGW host website (34). The 3-D IGW model (Version 4.7) developed for the Bradenton ASR site was based on a six-layer system. Layer one repr esents the surficial aquifer. Layers two and three represent a confining layer and producing zone of the inte rmediate aquifer, respectively. Layer four

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32 represents the ASR storage zone. Layer five re presents the sub-ASR stor age zone and layer six represents the base of the model domain. Th e horizontal boundary of each layer was assigned a constant head that corresponded to the initial head given for each layer (Figure 3-4). Each layer was also assigned an initial concentration reflecting backgr ound TDS concentrations of 1200 mg/L. A constant source boundary was also applie d to the horizontal boundaries of layers three (i.e., intermediate producing zone), four (i.e., storage zone), an d five (i.e., sub-ASR layer) to represent background TDS conditions (1200 mg/L) dur ing large-volume recovery events. Layer six was assigned a constant head, equal to the in itial head, and a consta nt source to represent background TDS conditions. The parent-model domain was set at 9600 by 9600 f eet with a course grid spacing of 282.4 feet (35 x-grids and 35 y-grids). A sub-model, with a fine grid spacing of 43.2 by 44.2 feet (40 x-grids and 40 y-grids), was used to increase the resolution (i.e., discretization) of the parentmodel in the vicinity of the ASR well. The injection/pumping well (ASR-1) well was located in the center of the model domain (i.e., x-direct ion = 4800 feet, y-direct ion = 4800 feet). To monitor horizontal flux during ASR a storage zone monitoring representing SZMW-1 was located 224 feet north (i.e., plus 224 feet in y-direction) of ASR1. To monitor vertical flux during ASR, an intermediate aquifer monito ring well representing AFWM-1 was located 20.4 feet east (i.e., plus 24 feet in x-direction) of ASR-1 and a water table monitoring well representing WTMW-1 was located 11.2 feet east of ASR-1 A dditional details of the model layers and attributes ar e provided in Figure 3-4. The default model solver settings were used to calibrate the model and run simulations. The default settings include th e Algebraic Multigrid flow solver and the Successive Over Relaxation (SOR) transport solver. The mode l was calibrated against both TDS breakthrough

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33 curves and heads measured at ASR-1, SZMW-1, and AFMW-1, and heads measured at WTMW1, during Cycle Tests 5, 6, a nd 6a. Numerous simulations we re run with additional model refinement during model calibration. Calibrati on of the model was achieved with the model attributes listed in Figure 3-4. Once calibrated, the model was run to simulate successive operational cycles at the Bradenton ASR Site over a four-year period. These cycles were based on the initial design of the Bradenton facility with 150 MG recharged durin g the wet season and 120 MG recovered during the following dry season. However, the model doe s not consider loss due to drift under natural aquifer gradients as storage in tervals were not simulated.

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34 Figure 3-1. Site location map (modi fied from Jones Edmunds (20))

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35 Figure 3-2. Site plan (modified from Jones Edmunds (20))

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36 Ocala Limestone Hawthorn Group Suwannee Limestone WTMW-1 AFMW-1 ASR-1 SZMW-1 TD 550 feet TD 505 feet TD 230 feet 17.4 inch Dia. PVC Casing to 417 feet 8-inch Dia. PVC Casing to 200 feet 6-inch Dia. PVC Casing to 403 feet 224 ft 20.4 ft 11.2 ft Avon Park Formation 0 ft 100 ft 200 ft 300 ft 400 ft 500 ft 600 ft 700 ft 800 ft 900 ft 1000 ft 1100 ft 1200 ft 4-inch Dia. PVC Casing to 15 feet Elevation (ft bls) Figure 3-3. Generalized geologic profile and well construction details (modified from Jones Edmunds (20)). Vertical scale greatly exaggerated Sub-ASR Interval Confining Unit Storage Zone ASR-1 SZMW-1 Base Layer 18 ft 17 ft -182 ft 397 ft 487 ft -1200 ft -1300 ft Productive Unit AFMW-1 kxy = 0.1 kx/kz = 100 n = 0.01 hi = 14 kxy = 46 kx/kz = 100 n = 0.08 hi = 15 kxy = 30 kx/kz = 100 n = 0.02 xyz = 100 s = 1.2e-6 hi = 20 kxy = 10 kx/kz = 10 n = 0.15 hi = 13.3 kxy = 30 kx/kz = 100 n = 0.02 hi = 20 kxy = 30 kx/kz = 100 n = 0.02 xyz = 100 s = 1.2e-6 hi = 20 Surficial Aquifer WTMW-1 Elevation (ft NGVD) Figure 3-4. Model details and input parameters

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37 Table 3-1. Well construction details for the Bradenton HSPS ASR facility Well Name Casing Depth (feet blsa) Nominal Casing Outside Diameter (inches) Casing Material Open Hole Interval (feet blsa) Top of Well Casing Elevationb (mslc) ASR-1 415 17.4 PVC 415-550 (plugged back with cement to 505) 20.54 SZMW-1 400 6.625 PVC 400-548 20.16 AFMW-1 200 8.625 PVC 200-230 19.58 WTMW 15 4 PVC screened from 5-15 20.26 a = feet below land surface (bls); b = as surveyed on October 8, 2003; c = feet above mean sea level (msl) (Jones Edmunds (20)) Table 3-2. Bradenton ASR cycle test program summary Cycle Test Start Date End Date Storage Duration (Days) Average Recharge / Recovery Rates (MGD) Recharge Volume (MG) Recovery Volume (MG) Net Volume (MG) 1 9/9/2004 12/1/2004 9 1.69 / -1.87 10.25 10.39 0 2 12/1/2004 12/20/2004 6 1.67 / -1.87 10.02 10.63 0 3 12/24/2004 1/19/2005 13 1.67 / 1.87 9.97 10.03 0.06 4 1/20/2005 3/1/2005 28 1.65 / 1.78 9.36 9.37 0 5 8/9/2005 9/22/2005 0 1.38 / -1.43 50.18 8.89 41.29 Inter-Cycle Storage Period 18 6 10/11/2005 1/20/2006 0.9 1.30 / -1.53 120.1 10.15 151.24 Inter-Cycle Storage Period 56 6aa 3/21/2006 4/7/2006 -1.53 24.96 126.28 Inter-Cycle Storage Period 10 6aa 4/18/2006 6/23/2006 -1.51 94.93 31.35 a = Cycle Test 6a was interrupted due to FDEP permitting issues

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38 CHAPTER 4 RESULTS Water Chemistry Background water quality samples were collected at SZMW-1 during the startup of Cycle Test 1 (Table 4-1). With th e exception of chloride concentr ations, native groundwater at the Bradenton Site is consistent with ambient water quality in the coastal UFA of southwest Florida (16). Native groundwater at the Si te contains high levels of di ssolved species as indicated by measured TDS and sulfate concentrations and is highly reduced (strongly negative field ORP values). The quality of the recharge water (injec tate) is consistent with potable water supplied by a conventional surface water treatmen t process. In contrast to native groundwater, the recharge water is well oxygenated, with consistently hi gh DO and ORP values, and contains relatively low concentrations of dissolved constituents such as sulfate, calcium, magne sium, and arsenic (Table 4-1). Chloride in UFA groundwater of coastal southwest Florida often exceeds 750 mg/L (16), while recharge water for potable ASR systems is generally less than the SDWS of 250 mg/L. However, this was not the case for Bradenton as the background concentrati on of chloride in the UFA is close to that of the recharge water (Table 4-1). Therefore, TDS was used as a tracer for this investigation. While TDS is not an idea l tracer, due to the reaction of DO with sulfur minerals in the UFA, the effect on the TDS c oncentration due to the dissolution of sulfur minerals is assumed to be negligible. Also, there is a clear contra st in the background TDS concentration in ASR-1 (approximately 1200 mg/L) and that of the recharge water (approximately 323 +/23 mg/L; see Table 4-1).

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39 Cycle Test Results Elevated arsenic concentrations, along with rapid DO consumption and ORP equilibration, indicate that a near-borehole geochemical response was measur ed at ASR-1 during Cycles 1-4 (Figures 4-1 and 4-2). Arseni c increased above the background concentration (<3 g/L) during each of the recovery events, with the highest value of 23 g/L reported during Cycle 3. DO concentrations decreased rapidly at ASR-1 during storage from rech arge water levels that were near or above saturated conditions (7.83 to 9.95 g/L) to less than 2.09 g/L at the end of each storage event. There were no significant changes in the water quality trends for arsenic, DO, or ORP measured at ASR-1 during the extended storag e period (29 day) of Cycle 4. Arsenic, DO, and ORP remained near background levels at SZMW-1 (r = 224 feet) during these small-volume tests. The TDS increased to near background condi tions (1200 mg/L) at ASR-1 during Cycle 1 recovery. However, TDS values did not reco ver to background conditi ons during subsequent tests (Figure 4-2). This may be attributed to mixing (loss due to dispersion) between the brackish native groundwater and lower salinity or fre sh potable water during ASR or loss due to the natural gradient during storage. The noticeable declin e in TDS concentrations at SZMW-1 during recharge events is likely th e result of preferential flow path s (Figure 4-2). This correlates with the high-permeability layer between 460 a nd 485 feet below land surface reported in the 2004 Construction Report (21). There was no storage period between the Cycl e 5 and 6 recharge a nd recovery events. This allowed for measurement of the rapid equi libration of ORP values and consumption of DO during ASR at the Bradenton Site (Figure 4-3) ORP values decreased from recharge water levels of 400 mv to approximately 100 mv in the recovered water durin g Cycle Test 5 and 6 recovery events. DO values ranged from 6.05 to 10.99 mg/L during Cycle Test 5 and 6 recharge

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40 events and decreased to background (0.02 mg/L) levels during both 10 MG recovery events. This is further evidence of the near-borehole ge ochemical response that results from the rapid shift in water quality conditions during ASR. As expected, ORP increased from highly reduced conditions (-100 to -200 mv) to more oxidized conditions (approximately 100 mv) at SZMW-1 during the Cycle 5 and 6 recharge events. DO valu es remained near the resolution of the probe (<0.02 mg/L) during Cycle 5 and 6 at SZMW-1 (Figure 4-3). The advective front was detected at SZMW-1 during the 50-MG recharge event of Cycle 5 as TDS decreased sharply to near recharge wate r concentrations between approximately 30 to 40 MG recharged and increased sh arply during the 10-MG recovery event (Figure 4-4). This indicates that, while loss due to mechanical disp ersion may be occurring, the transport of this parameter is not significantly influence or is not retarded by the limestone matrix. While results from Cycle Test 1 through 6 indi cate a near-borehole geochemical response that releases arsenic during AS R, arsenic remained near background levels at SZMW-1 during the Cycle 5 and 6 recharge events (Figure 4-5). This suggests that arsenic is retarded (absorbed) by the limestone matrix during aquifer recharge Arsenic concentrations increased above background levels at SZMW-1 during Cycle 5 re covery and storage, which may indicate reductive dissolution of arsenic is occurring. Other than a slight increase in arsenic concentrations, there was no signifi cant change in water quality, fr om recharge water levels, at ASR-1 during the 10-MG Cycle Test 5 a nd 6 recovery events (Figure 4-4). TDS increased steadily at ASR-1 during Cycle 6a and approached background levels near the end of the recovery event (Figure 4-5). Th e broad, shallow slope TDS trend indicates a high degree of mixing (loss) during ASR at the Bradent on Site. Arsenic was detected at or slightly greater than background concen trations at ASR-1 during th e beginning of both Cycle 6a

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41 recovery events, which is similar to the tre nd shown during the Cycle Test 5 and 6 recovery events. Arsenic concentrations spiked up to 75 g/L during recovery at ASR-1 indicating dissolution of pyrite during ASR. Data Collected at SZMW-1 during Cycle 6a sh ows TDS increasing at a rate similar to the concentrations measured at ASR-1 (Figure 4-5). However, TDS reached stability at 990 to 1000 mg/L at SZMW-1 near the end of the recovery event. Arsenic concentrations increased above the MCL at SZMW-1 during Cycle 6a w ith the highest concentration of 20 g/L detected at approximately 105 MG recovered. Arsenic concentr ations were not detected at these levels At SZMW-1 during the Cycle Test 5 and 6 recharge events (Figure 4-5). This suggests reductive dissolution of arsenic occu rs during ASR. Arsenic levels re mained elevated after the end of Cycle 6a recovery (Figure 4-5). Based on this, it appears that arsenic released during the ASR recovery phase does not rapidly r eabsorb to the matrix and, therefore, remains in a dissolved (mobile) state after ASR recovery. PPT Results To demonstrate the application of the met hod proposed by Haggerty (31) to ASR Cycle Tests, we apply this method to estimate DO decay rates in ASR. Using measured concentrations for C*r (field DO values) and C*tr (TDS lab data ) collected during cycle tests conducted at the Bradenton ASR Site, we estimated DO decay rates as follows (see Figure 4-6): Cycle 1 decay rate (k) = 0.43/day Cycle 2 decay rate (k) = 0.43/day Cycle 5 decay rate (k) = 0.72/day Cycle 6 decay rate (k) = 0.41/day The decay rates estimated for Cycles 1, 2 a nd 6 fall within a narrow range of 0.41/day to 0.43/day. However, the decay rate estimated for Cycle 5 was much higher at 0.72/day. This increase may be attributed to an increase in recharge water temperature during Cycle 5.

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42 Prommer and Stuyfzand (36) measured the temperat ure dependency of reactions with dissolved oxygen during deep well injection at th e Dizon Site in the Netherlands. Bradenton Cycle Tests 1, 2, and 6 were comp leted during the winter months, while Cycle Test 5 was completed during late summer. The following average recharge water temperatures were measured during these tests: Cycle 1 = 24.34C 0.59 Cycle 2 = 22.18C 0.57 Cycle 5 = 30.12C 0.48 Cycle 6 = 22.60C 3.50 The dependence of the rate coefficient (k) on temperature can be evaluated by applying the vant Hoff equation (37) 2 11211 lnT r Tk kRTT (4.1) where 2Tkand 1Tkare empirically derived rate coefficients, r is the molar enthalpy of reaction, R is the universal gas constant, and T is temperature. Solving equation (4.1) 2 112ln 11T T rk R k TT (4.2) given Cycle 5 kT1 = 0.72/day at T1 = 30.12 C (303.12 K) and Cycle 6 kT2 = 0.41/day at T2 = 22.18C (295.18 K) we calculate r for this system to be 52.75 kJ/mol. Assuming r is constant (independent of temperature), given kT1 = 0.72/day at T1 = 30.1 C (303.1 K) for Cycle 5, we now solve equation (4.2) for kT2 for 25 C (298 K), As calculated, the decay rate for DO in this system at 25 C (298 K) is estimated to be 0.50/day.

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43 The temperature dependence of the reaction rate can also be evaluated by plotting ln K versus 1/T (37). When plotted, the Bradenton Cycle Test data fit the linear equation ln k = 6279.6 K/T +20.365, with slope equal to r / R (see Figure 4-7). Therefore, r for this system equals 52.21 kJ/mol. Plugging a value of T = 25C (298K) into the equation of the line (ln k = -6279.6 K/T +20.365) given by the vant Hoff plot, we estima te k at 25 C to be 0.49/day, which is close to the value calculated above. Breakthrough (recovery) curves can also be useful for characterizing ASR systems. Breakthrough curves for species of interest at the Bradenton ASR Site are shown in Figure 4-8. Sulfate, magnesium, calcium,and TDS are present in high concentrations in the native groundwater of the Bradenton Site as compared to the concentrations of th ese parameters in the injected water (Table 3-1). Therefore, the incr ease in the concentration of these parameters during recovery is driven by mixing between the native water and injected water. The broad slope of these curves indicates that the Br adenton ASR-1 system behaves as a well-mixed reactor. The curves for these parameters also show an early breakth rough, with an initial increase around 22% recovered (Vext/Vinj = 0.22). This indicates that, while mixing or loss in this system is primarily governed by dispersion, the transport of these parameters is primarily driven by advection with little retardation in the matrix. Arsenic is not present at high concentrations in the native water or injected water at the Bradenton Site. Therefore, the high concentratio n of arsenic in the reco vered water is due to mobilization of arsenic from the aquifer matrix. In contrast to sulfate, magnesium, calcium and TDS, arsenic has a fairly steep breakthrough wi th an initial increas e around 40% recovered (Vext/Vinj = 0.40). This indicates that mobilized arse nic is retarded within the matrix, with respect to TDS.

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44 An explanation of the spiky pattern of th e breakthrough curve with multiple peaks shown in the recovery curves for arsenic and sulfide is that the aquifer consis ts of two zones having different hydraulic properties. Based on this, the two peaks of the curve represent two different rates of groundwater velocities. Alternatively, the multiple peaks may be an artifact of cycle testing where the build-out of th e storage volume occurred in two successive but separate events. First, during Cycle 5, 50 MG was recharged w ith 10 MG recovered. After an 18-day storage period, Cycle 6 recharge was initiated, wh ich included 120 MG recharged with 10 MG recovered. That is, the interim recovery of 10 MG increased mixing or loss due to dispersion separating the Cycle 5 front from the Cycle 6 front. IGW Model Results The 3-D IGW model was successfully calibrated to the TDS values measured at the storage zone monitoring well SZMW-1 during Cycle Test 5, 6, and 6a given the input parameters (i.e., aquifer properties) presented in Figure 3.7. Th e measured and simulated TDS curves at SZMW1 for the Cycle Test 5 recharge event are very si milar (Figure 3.9). However, there is a slight separation (lag) from the measured and simulate d TDS values at SZMW-1 during the Cycle Test 5 and Cycle Test 6 recovery events. This is possibly due to an increase in dispersion ( ) as, during recharge, the water moves past the monitori ng well (SZMW-1) out to the lateral extent of the stored water. The model derived TDS breakthrough curves for ASR-1 are similar to the simulated curves for SZMW-1 (Figure 4-10). However, the TDS va lues measured at ASR-1 during the Cycle Test 6a recovery event showed that breakthrough is de layed at ASR-1 with a slope steeper than that measured at SZMW-1 (Figures 4-9 and 4-10). Th is may be a result of the vertical gradients measured at ASR-1 during recharge and recovery that may be rela ted to the well efficiency (i.e.,

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45 loss) previously discussed. Dispersion also likely plays a significant, if not dominant, role in the shape and height of the breakthrough curves. Vertical flux was simulated by calibrating the IGW model to the TDS values measured at monitoring well AFMW-1 during Cycle Tests 5-6a (Figure 4-11). While the simulated TDS values are slightly lower than the measured values, the model successfully accounts for the vertical movement (loss) of solute during recharge events by the fresheni ng of the intermediate aquifer. The 3-D IGW model calibrated closely to th e heads measured at SZMW-1 and AFMW-1 during Cycle 5 (Figure 4-12). Howe ver, there is a separation from the heads measured at ASR-1 and the simulated results. This is possibly due to well loss (i.e., bore-hole loss) at ASR-1 as the model does not account for well efficiency. Jones Edmunds (21) reported a well-loss coefficient of 2.6E-5 ft/gpm2, while pumping ASR-1 at 1274 gpm during the initial well tests. Jones Edmunds (21) calculated that du ring the initial tests 45 feet of the measured 127 feet of drawdown in this well was due to well loss. Once calibrated, the 3-D IGW model was used to evaluate the TSV approach for managing recovery efficiency at the Br adenton ASR facility. Simulated results for four full-scale operational cycles (i.e., Cycle 5-6a Cycle7, Cycle 8, and Cycle 9) at the Bradenton ASR facility are presented in Figure 4-13. The peak TDS values predicated by the mode l, which represent the end of the recovery events, decreases from 980 mg/L during Cycle 5-6a to 841 mg/L during Cycle 9 (Figure 4-13). These resu lts indicate that the TSV opera tional approach (i.e., recharging 150 MG and recovering 130 MG annua lly) can increase the recovery efficiency of the Bradenton ASR site.

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46 -500 -400 -300 -200 -100 0 100 200 300 400 50010/27/04 11/03/04 11/10/04 11/17/04 11/24/04 12/01/04 12/08/04 12/15/04 12/22/04 12/29/04 01/05/05 01/12/05 01/19/05 01/26/05 02/02/05 02/09/05 02/16/05 02/23/05 03/02/05Oxidation Reduction Potential (mv) (For eH value add 200 mV)0 2 4 6 8 10 12Dissolved Oxygen (mg/L) ASR-1 ORP SZMW-1 ORP ASR-1 DO SZMW-1 DO CYCLE 2CYCLE 3CYCLE 4 CYCLE 1 Figure 4-1. Field parameters m easured during Cycle Tests 1-4 0 5 10 15 20 2510/27/04 11/03/04 11/10/04 11/17/04 11/24/04 12/01/04 12/08/04 12/15/04 12/22/04 12/29/04 01/05/05 01/12/05 01/19/05 01/26/05 02/02/05 02/09/05 02/16/05 02/23/05 03/02/05Arsenic Concentration (g/L)0 200 400 600 800 1000 1200TDS Concentration (mg/L) ASR-1 Arsenic (ELab) ASR-1 Arsenic (COB Lab) SZMW-1 Arsenic ASR-1 TDS SZMW-1 TDS CYCLE 2CYCLE 3CYCLE 4 CYCLE 1 Figure 4-2. Analytical parameters reported for Cycle Tests 1-4

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47 -500 -400 -300 -200 -100 0 100 200 300 400 50007/20/05 08/03/05 08/17/05 08/31/05 09/14/05 09/28/05 10/12/05 10/26/05 11/09/05 11/23/05 12/07/05 12/21/05 01/04/06 01/18/06 02/01/06Oxidation Reduction Potential (mV) (Field YSI 556 MPS) (For eH value add 200 mV)0.00 2.00 4.00 6.00 8.00 10.00 12.00Dissolved Oxygen (mg/L) ASR-1 ORP SZMW-1 ORP ASR-1 DO SZMW-1 DO CYCLE 5CYCLE 6 Figure 4-3. Field parameters meas ured during Cycle Tests 5 and 6 0 200 400 600 800 1000 120007/20/05 08/03/05 08/17/05 08/31/05 09/14/05 09/28/05 10/12/05 10/26/05 11/09/05 11/23/05 12/07/05 12/21/05 01/04/06 01/18/06 02/01/06TDS (mg/L)0.0 5.0 10.0 15.0 20.0Arsenic (ug/L) ASR-1 TDS SZMW-1 TDS ASR-1 -Arsenic SZMW-1 -Arsenic CYCLE 5CYCLE 6 Figure 4-4. Analytical parameters reported for Cycle Tests 5 and 6

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48 0 300 600 900 120003/14/06 03/28/06 04/11/06 04/25/06 05/09/06 05/23/06 06/06/06 06/20/06 07/04/06 07/18/06TDS Concentration (mg/L)0.0 20.0 40.0 60.0 80.0Arsenic (ug/L) ASR-1 TDS SZMW-1 TDS ASR-1 Arsenic SZMW-1 Arsenic Cycle 6a Figure 4-5. Analytical parameters reported for Cycle Test 6a -6.00 -5.00 -4.00 -3.00 -2.00 -1.00 0.00 0.002.004.006.008.0010.0012.00 Time Since Injection Ended (Days)Ln (Cr/Ct) Cycle 5: (y = -0.7220x 0.2443; R^2 = 0.9893) Cycle 6: (y = -0.4126x 0.3549; R^2 = 0.951) Cycle 1: (y = -0.4293x 0.0749; R^2 = 0.9975) Cycle 2: (y = -0.4329x + 0.5303; R^2 = 0.8599) Figure 4-6. Plot of ln(C*r(t)/C*t r(t)) versus t* for Bradenton ASR Cycles Tests 1, 2, 5, and 6. Decay rates (k) are estimated as th e negative of the slope of the line

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49 C6 C1 C5 C2y = -6279.6x + 20.365 R2 = 0.933-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0 3.29E03 3.30E03 3.31E03 3.32E03 3.33E03 3.34E03 3.35E03 3.36E03 3.37E03 3.38E03 3.39E03 3.40E031/T (T in K)Ln k Figure 4-7. vant Hoff Plot of Br adenton ASR cycle test data 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.000.100.200.300.400.500.600.700.800.90 Volume Extracted / Volume InjectedRelative Concentration (C(t) Cin / Cmax -Cin) Arsenic Sulfate TDS Magnesium Calcium Figure 4-8. PPT breakthrough curve for Bradento n ASR. Parameter concentrations were measured during Cycle 6 and Cycle 6a recovery events

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50 0 200 400 600 800 1000 1200 14000 50 100 150 200 250 300 350Elapsed Time (days)TDS (mg/L) IGW SZMW-1 TDS SZMW-1 TDS CYCLE 5 CYCLE 6 CYCLE 6a Figure 4-9. IGW model calibration results for TD S measured at SZMW-1 during Cycle Tests 56a 0 200 400 600 800 1000 12000 50 100 150 200 250 300 350Elapsed Time (days)TDS (mg/L) IGW ASR-1 TDS ASR-1 TDS CYCLE 5 CYCLE 6 CYCLE 6a Figure 4-10. IGW model calibration results for TD S measured at ASR-1 during Cycle Tests 5-6a

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51 0 200 400 600 800 1000 1200 14000 50 100 150 200 250 300 350Elapsed Time (days)TDS (mg/L) IGW SZMW-1 TDS SZMW-1 TDS CYCLE 5 CYCLE 6 CYCLE 6a Figure 4-11. IGW model calibration results for TDS measured at AFMW-1 during Cycle Tests 5-6a Cycle Test 5 Heads-20 -15 -10 -5 0 5 10 15 20 25 300 5 10 15 20 25 30 35 40 45Elapsed Time (days)Heads (m) IGW ASR-1 Heads SZMW-1 Heads AFMW-1 Heads IGW AFMW-1 Heads ASR-1 Heads IGW SZMW-1 Heads Figure 4-12. IGW model calibration results for water levels measured at SZMW-1, AFMW-1, and ASR-1 during Cycle Test 5

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52 200 400 600 800 1000 12000 100 200 300 400 500 600 700 800 900Elapsed Time (days)TDS (mg/L) IGW ASR-1 TDSCYCLE 5-6aCYCLE 7 CYCLE 9 CYCLE 8 Figure 4-13. Simulated results for full-scale operations at the Br adenton ASR facility Table 4-1. Bradenton ASR water quality summary Sample Location SZMW-1a ASR-1b ORP (mV) -264 359 32 Field Parameters DO (mg/L) 0.02* 8.44 1.63 Chloride (mg/L) 38 30 4 Sulfate (mg/L) 640 154 9 Magnesium (mg/L) N/A 8.8 1.1 TDS (mg/L) 1200 323 23 Laboratory Parameters Arsenic (g/L) <2.8 <1.32 aBackground (i.e., native) water quality results as measured on 11/9/2003 bAverage recharge water quality concentra tions measured during Cycle Test 5 and 6 measured value is at the reso lution of the probe reported by th e instrument manufacturer YSI.

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53 CHAPTER 5 CONCLUSIONS Results from the Bradenton ASR cycle tests and the PPT analytical techniques used in this research suggests a rapid near-borehole geoche mical response occurs during ASR injection, with calculated First-order DO decay rates ranging fr om 0.41/day to 0.72/day. Other PPT analytical techniques, beyond those presented he re, may also be applied to ASR. The pump and drift PPT approach presented by Hall et al. (28) may be useful to quantify ground water velocity(s) during ASR and calculate storage zone effective poros ity, given adequate groundwater level monitoring for determining local hydraulic gradients. Thes e methods may be adapted to help ASR operators demonstrate compliance with the current regulato ry position on arsenic, help the practitioner optimize the ASR facility, and pr ovide new methods for research scientists working to resolve these technical issues. To quantify the near-borehole geochemical resp onse that occurs during ASR, a series of small volume cycle tests, base d on the PPT method, should be conducted before large-volume cycle testing. The scale of th e tests should be based on site-sp ecific conditions. However, a likely range for the volumes of the initial test sh ould be 10 to 30 MG recharged with no storage. The initial test should be sized to fit the ASR system, including the number and location of monitoring wells, estimated porosit y, storage interval thickness, and planned ASR operations (e.g., recharge and recovery rates). Recovery sh ould be more than 100% of the injected volume to allow for complete breakthrough of reactants, pr oducts, and tracers. Subsequent cycles should be larger scale tests, in term s of recharge and recovery volumes, to focus on the geochemical response that occurs as water m oves past storage zone monitoring well(s) and to estimate the recovery efficiency of the system.

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54 While the results from Cycle Testing at th e Bradenton Site correlate well with the conceptual model for arsenic mobilization during ASR presented here, uncertainty remains regarding the mechanisms controlling the fate and transport of arsenic. Additional research is needed to identify the potential mechanisms controlling arsenic transport during ASR. Based on the results of the IGW Model, chem ical gradient controls, such as the TSV approach, were found to be a reasonable means of managing the recovery efficiency of the Bradenton ASR facility. By allowing for an ini tial loss of recharge water, a relatively shallow chemical gradient can be established, increasing the recovery efficiency of subsequent cycles. Arsenic was detected above the drinking water standard at the Bradenton ASR site in the ASR well (ASR-1) during Cycle Test s 1 through 4 and Cycle Test 6a and at the storage zone monitoring well (SZMW-1) during Cycle Test 6a Therefore, the TSV approach does not adequately address the current re gulatory position on ar senic in ASR, where compliance with the arsenic standard must be met at all points and all times in the aquifer. Given this, alternative methods must be considered. While beyond the sc ope of this research, such methods may be evaluated in future studies.

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55 LIST OF REFERENCES (1) Henry, J. A.; Portier, K.M.; Coyne, J. The Climate and Weather of Florida Pineapple Press, Inc: Sarasota, FL, 1994. (2) Winsberg, M. D.; OBrien J. J. ; Zierden, D. F.; Griffin, M. L., Florida Weather 2nd Edition, University of Florid a Press: Gainesville, FL, 2003. (3) SJRWMD, SFWMD, SWFMWD, Recommended Action Plan for the Central Florida Coordination Area: A Cooperative Effort of the South Florida, Southwest Florida and St. Johns River Water M anagement Districts September 18, 2006, Available for download at: http://sjr.state.fl.us/programs/watersupply.html (4) Green III, K. B. The Present and Future Role of ASR in the St Johns River Water Management District, Keynote Address, Aquifer Storag e Recovery VI Conference, Orlando, FL, hosted by American Groundwater Trust, October 2006 (5) Florida Administrative Code. Undergr ound Injection Control, F.A.C. 62-528, 54 pp. Accessed April 10, 2007, Available for download at: http://www.dep.state.fl.us/lega l/Rules/shared/62-528/62-528.pdf (6) Florida Administrative Code. Groundwater Classes, Standards, and Exemptions, F.A.C 62-520, 13pp. Accessed April 10, 2007, also available for download at: http://www.dep.state.fl.us/lega l/Rules/shared/62-520/62-520.pdf (7) Florida Administrative Code. Drinking Water Standards, Monitoring, and Reporting. F.A.C. 62-550, 50 pp. Accessed April 10, 2007, Available for download at: http://www.dep.state.fl.us/lega l/rules/drinkingwater/62-550.pdf (8) Istok, J. D.; Humphrey, M. D.; Schroth, M. H.; Hyman, M. R.; OReilly, K. T. SingleWell, Push-Pull Test for In Situ Determination of Microbial Activities, Groundwater 1997, 35 (4), 619-631. (9) Arthur, J. D.; Dabous, A. A.; Cowart, J. B. Water Rock Geochemical Considerations for Aquifer Storage and Recovery; Florida Case Studies. In Underground Injection Science and Technology, Developments in Water Science ; Tsang, C.F., Apps, J.A., Eds.; Elsevier: Amsterdam, 2005, 52 327-339. (10) Arthur, J. D.; Dabous, A. A.; Cowart, J. B. Mobilization of Arsenic and Other Trace Elements During Aquifer Storage and Recovery, Southwest Florida; Open-File Report 02-89; U.S. Geological Survey, Sacramen to, CA, 2002. Available for download at: http://water.usgs.gov/ogw/pubs/ofr0289/ (11) Pyne, D. The Target Storage Volume (TSV): A Proven Approach for Achieving High Recovery Efficiency and for Attenuating Arsenic Aquifer Storage Recovery VI Conference, Orlando, FL, hosted by Amer ican Groundwater Trust, October 2006

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56 (12) Richtar, J. Regulatory Update Permitting Requirements for Operating ASR Investigations and Projects Aquifer Storage Recovery VI, Aquifer Storage Recovery VI Conference, Orlando, FL, hosted by Amer ican Groundwater Trust, October 2006 (13) Williams, H.; Cowart, J. B.; Arthur, J. D. Florida ASR Geochemical Study, S.W. Florida: Year One and Two Progress Report. Florida Geological Surv ey, Tallahassee, FL, 2002. (14) Price, R. E.; Pichler, T. Abundance and Mineralogical Associati on of Arsenic in the Suwannee Limestone (Florida): Implicatio ns for Arsenic Release During Water-Rock Interaction Chem. Geol 2006, 228 44-56. (15) Smedley, P. L.; Kinniburgh, D. G. A Review of the Source an d Behavior and Distribution of Arsenic in Natural Waters U.N. Synthesis Report on Ar senic in Drinking Water; World Heath Organization: Geneva, 2001. (16) Jones, G. W.; Pichler, T. Relationship between Pyrite Stability and Arsenic Mobility During Aquifer Storage and Recovery in Southwest Central Florida. Environ. Sci. Technol 2007, 41 723-730. (17) Welch, A. H.; Stollenwerk, K. G. Arsenic in Groundwater, Geochemistry and Occurrence; Kluwer Academic Publishers: Norwell, MA, 2003 (18) Mirecki, J. E. Geochemical Models of Water-Qua lity Changes During Aquifer Storage Recovery (ASR) Cycle Tests, Phase I: Ge ochemical Models Using Existing Data. ERDC Technical Report 2006, U.S. Army Engineer Research and Development Center, Vicksburg, MS. (19) Parkhurst, D. L.; Appelo, C. A. PHREEQC (Version2)A Co mputer Program For Speciation, Batch-Reaction,One-Dimensional Transport, and Inverse Geochemical Calculations ; Water-Resources Investigations Repor t 99-4259; U.S. Geological Survey, Denver, CO, 1999. Available for download at: http://wwwbrr.cr.usgs.gov/pr ojects/GWC_coupled/phreeqc/ (20) Jones Edmunds & Associates, Inc., Bradenton ASR, Cycle Test Summary Report October, 2006. (21) Jones Edmunds & Associates, Inc. and ASR Systems, LLC. City of Bradenton, ASR Program, Phase II Well Construction Report February, 2004. (22) DelCharco, M.J.; Lewelling, B.R. Hydrologic Description of the Braden River Watershed, West-Central Florida : U.S. Geological Survey Open-File Report 96, 1997, 34 p. (23) Peek, Harry M. Ground-water Resources of Manatee County, Florida Report of Investigations No.18; Florida Geol ogical Survey, Tallahassee, FL, 1958. (24) Yobbi, D.K., and Halford, K.J. Numerical Simulation of Aquifer Tests, West-Central Florida ; Scientific Investiga tions Report 2005-5201; U.S. Geological Survey, 2006.

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57 (25) McGuire, J. T.; Long, D. T.; Klug, M. J. ; Haack, S. K.; Hyndma n, D. W. Evaluating Behavior of Oxygen, Nitrate, and Sulfate during Recharge and Quantifying Reduction Rates in a Contaminated Aquifer. Environ. Sci. Technol 2002, 36 2693-2700. (26) Kim, Y.; Istok, J. D.; Semprini, L. Push-Pull Tests Evaluating In Situ Aerobic Cometabolism of Ethylene, Propylen e, and cis-1,2-dichloroethylene Journal of Contaminant Hydrology 2006, 82 165-181. (27) Leap, D. I.; Kaplan, P. G. A Singl e-Well Tracing Method for Estimating Regional Advective Velocity in A confined Aquife r: Theory and Preliminary Laboratory Verification, Water Resources Research 1988, 24, (7) 993-998. (28) Hall, H.; Luttrell, S. P.; Cronin, W. W. A Method for Estimating Effective Porosity and Ground-Water Velocity, Ground Water 1991, 29 (2), 171-174. (29) Scroth, M. H.; Istok, J. D.; Haggerty, R. In Situ Evaluation of Solute Retardation using Single-Well Push-Pull Test s, Advances in Water Resources 2001, 24 105-117 (30) Scroth, J. D.; Schroth, M. H. Models to Determine First-Order Rate Coefficients from Single-Well Push-Pull Tests, Ground Water 2006, 44 (2) 275-283. (31) Haggerty, R.; Schroth, M. H.; Istok, J.D. Simplified Method of Push-Pull Test Data Analysis for Determining In Situ Reaction Rate Coefficients, Ground Water 1998, 36 (2) 314-324. (32) Jury, W. A.; Roth, K. Transfer Functions and Solute Movement through Soil Birkhauser Verlag, 1990, Boston, MA. (33) Li, S.G., Q. Liu, and S. Afshari, An Object-Oriented Hierarch ical Patch Dynamics Paradigm (HPDP) for Groundwater Modeling. Environmental Modeling and Software 2006, 21 (5), 601-758. (34) Li, S.G. and Q. Liu, Software News Interactive Ground Water (IGW), Environmental Modeling and Software 2006, 21 (3), (35) Li, S. G., Liu, Q. Interactive Ground Wa ter (IGW): An Innovative Digital Laboratory For Groundwater Education and Research, Computer Applications in Engineering Education 2003, 11 (4), 179-202, Available for download at http://www.egr.msu.edu/igw/ (36) Prommer, H.; Stuyfzand, P. J. Identifi cation of temperature-de pendent water quality changes during a deep well injection experiment in a pyritic aquifer. Environ. Sci. Technol. 2005, 39 2200-2209. (37) Benjamin, M. M. Water Chemistry ; McGraw-Hill Higher Education: New York, 2002

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58 BIOGRAPHICAL SKETCH Stuart Bryan Norton was born on November 21, 1973 in Clinton, North Carolina. At the age of 16, Stuart and his family moved to Manda rin, a suburb of Jacksonville, Florida. While spending time with friends who owned a small e nvironmental consulting firm, he developed a strong interest in environmental science and a deep respect for the environment. After graduating from Mandarin High School, he attended the University of Florida where he earned a Bachelor of Arts de gree in geology in 1998. In 1999 Stuart began his career with the cons ulting engineering firm Mactec, Inc. At Mactec, Stuart worked as a field geologist completing numer ous rapid site assessments, implementing remedial actions, and performing post-closure assessments at industrial, petroleum, and dry-cleaner sites in Florida. In 2001 Stuart began working with the Florida-based consulting engineering firm Jones, Edmunds & A ssociates, Inc. During his tenure with Jones Edmunds & Associates, Inc., Stuart has been wo rking towards his Master s of Science degree in environmental engineering sciences. His r ecent work experience includes both managing ASR and other water supply projects and wo rking as the project technical lead. Upon completion of his M.S. program, Stuart will begin working toward a Ph.D. in environmental engineering sciences at the Univers ity of Florida. His Ph.D. research focus will include geochemistry and groundwater hydrology w ith a specific emphasis on arsenic in ASR. The Ph.D. program will be an extension of the research presented in this thesis. Stuart married Gladys Enid Santana in 2004, wi th whom Stuart spends much of his free time. The couple regularly pursu es leisure interests including traveling, fishing, canoeing, tailgating at University of Flor ida Gator football home games, and numerous other outdoor activities.