Final Preliminary Feasibility Study Technical Memorandum for the North Site Groundwater Banking Project

Transcription

1 PREPARED FOR STOCKTON EAST WATER DISTRICT Final Preliminary Feasibility Study Technical Memorandum for the North Site Groundwater Banking Project FEBRUARY 2014

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3 TABLE OF CONTENTS 1.0 INTRODUCTION SITE DESCRIPTION PILOT-SCALE RECHARGE TESTING ORGANIZATION OF THIS TECHNICAL MEMORANDUM SUMMARY OF PRELIMINARY ACTIVITIES INITIAL SITE SCREENING ACTIVITIES PILOT-SCALE RECHARGE TESTING PREPARATORY ACTIVITIES PHASE I ENVIRONMENTAL SITE ASSESSMENT INITIAL STUDY AND NEGATIVE DECLARATION PERMITS UNDERGROUND SERVICE ALERT PILOT-SCALE RECHARGE TESTING WATER SOURCE SUMMARY OF FINDINGS OF PRELIMINARY ACTIVITIES SUMMARY OF PREVIOUS FIELD INVESTIGATIONS AQUIFER TEST AT EVALUATION PILOT SCALE RECHARGE TESTS AT THE FORMER 35-ACRE SITE FIELD INVESTIGATIONS AT THE NORTH SITE PRE-PILOT-SCALE RECHARGE TEST FIELD ACTIVITIES AND MONITORING MONITORING WELL DRILLING, COMPLETION, AND DEVELOPMENT Lithologic Data Grain Size Analysis WATER QUALITY SAMPLING Monitoring Wells Source Water GROUNDWATER ELEVATION MONITORING DESIGN, LOCATION, AND CONSTRUCTION OF PILOT-SCALE RECHARGE TEST RECOMMENDED RECHARGE TECHNIQUES FOR PILOT-SCALE RECHARGE TESTING SELECTION OF PILOT-SCALE RECHARGE TEST LOCATIONS CONCEPTUAL PILOT-SCALE RECHARGE BASIN DESIGNS SPREADING BASIN CONSTRUCTION AND ACTIVITIES Spreading Basins Water Source, Conveyance, and Measuring Devices Site Safety PILOT-SCALE RECHARGE TESTING RESULTS AND ANALYSIS PILOT-SCALE RECHARGE TESTING DATA Pilot-Scale Recharge Test Source Water Field Parameters Spreading Basin Water Depths Groundwater Depth Data Groundwater Quality Data Microscopic Particulate Analysis Stockton East Water District i February 2014

4 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project Evaporation and Precipitation Site Conditions GROUNDWATER ELEVATIONS GROUNDWATER QUALITY SPREADING BASIN RECHARGE PONDS Pond Depth Percolation Rates Cumulative Percolation Volumes Decommissioning of Pilot-Scale Recharge Test Facilities GROUNDWATER MOUNDING CONCLUSIONS GROUNDWATER QUALITY PERCOLATION RATES GROUNDWATER LEVEL RESPONSE DRAWDOWN SUMMARY GEOLOGY AND SOILS LAND USE SOURCE WATER GROUNDWATER CONDITIONS HABITAT ISSUES RECOMMENDATIONS REFERENCES February 2014 ii Stockton East Water District

5 Table of Contents LIST OF FIGURES Figure 1-1. Groundwater Recharge Program Site Area Map Figure 3-1. Locations of Guelph Permeameter Testing, Monitoring Wells, Production Wells, Pilot-Scale Recharge Testing, and Demonstration Testing in Vicinity of North Site Figure 4-1. Monitoring Well Completion Diagram Figure 4-2. Cross-Section from A-A Across the North Site Figure 5-1. Conceptual Drawing of Spreading Basin Figure 5-2. Spreading Basins at North Site Figure 6-1. Groundwater Depth Monitoring Figure 6-2. Groundwater Quality Monitoring Figure 6-3. Microscopic Particulate Analysis Apparatus Figure 6-4. Depth to Water vs. Time for Monitoring Wells Figure 6-5. Depth to Water vs. Time for SEWD Wells Figure 6-6. Depth of Water vs. Time for Test Pond Recharge Test Figure 6-7. Percolation vs. Time for Test Pond Recharge Test Figure 6-8. Cumulative Percolation Volume vs. Time for Test Pond Recharge Test Figure 7-1. Conceptual Locations of Seven New Extraction Wells and Existing Extraction Wells on or Near the North Site Stockton East Water District iii February 2014

6 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project LIST OF TABLES Table 3-1. Results of Aquifer Test Evaluation Table 3-2. Results of Guelph Permeameter Testing, Pilot-Scale Recharge Testing, and Demonstration Testing in Vicinity of North Site Table 4-1. Borehole Lithologic Data Table 4-2. Grain Size Analysis of Samples Collected from Boreholes Table 4-3. Summary of Baseline Water Quality Constituents Detected Table 6-1. Source Water Field Parameters Table 6-2. Summary of Post-Test Water Quality Constituents Detected Table 6-3. Summary of Post-Test Water Quality Constituents Detected at Neighboring Wells Table 6-4. Results of Microscopic Particulate Analysis Test Table 6-5. Hydraulic Properties Estimated from Pilot-Scale Recharge Testing Table 7-1. Results from Theis Equation Calculation Table 8-1. Geology and Soils Table 8-2. Land Use Table 8-3. Source Water Table 8-4. Groundwater Conditions Table 8-5. Habitat Issues February 2014 iv Stockton East Water District

7 Table of Contents Appendix A Data from Neighboring Wells Appendix B Pilot-Scale Field Recharge Plan APPENDICES (enclosed on CD) Appendix C Phase I Environmental Site Assessment, North Site (Bozzano Site) Appendix D San Joaquin County Permit Appendix E Well Completion and Well Development Forms Appendix F Lithologic Logs Appendix G Photo Log of Split Spoon Samples Appendix H Grain Size Analysis Appendix I Laboratory Water Quality Reports Appendix J Conceptual Pilot-Scale Recharge Basin Designs Appendix K Microscopic Particulate Analysis Data Sheet Stockton East Water District v February 2014

8 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project LIST OF ACRONYMS AND ABBREVIATIONS µg/l micrograms per liter µmhos/cm micro Siemens per centimeter ASTM American Society for Testing and Materials bgs below ground surface BMP best management practices Cal Water California Water Service Company CDPH California Department of Public Health CEQA California Environmental Quality Act CIMIS California Irrigation Management Information System City City of Stockton COC constituents of concern County San Joaquin County DHS California Department of Health Services DJWWTP Dr. Joe Waidhofer Water Treatment Plant EDR Environmental Data Resources EPA U.S. Environmental Protection Agency ESA Environmental Site Assessment ETo evapotranspiration ft/day feet per day ft/min feet per minute ft 2 /min feet squared per minute HAS hollow stem auger IS Initial Study MCL maximum contaminant levels mg/l milligrams per liter MPA microscopic particulate analysis MPN most probable number ND Negative Declaration NOD Notice of Determination PCB polychlorinated biphenyls PHG Public Health Goal Plan Water Bank Business Plan Program Manual Farmington Groundwater Recharge Program Manual REC recognized environmental conditions S approximated value using the Theis Solution for Recovery, is the ratio of storativity during pumping to storativity during recovery SDC Stockton Diverting Canal SEWD Stockton East Water District SJCEHD San Joaquin County Environmental Health Department TDS Total Dissolved Solids TM technical memorandum USA Underground Service Alert USCS Unified Soil Classification System USGS U.S. Geological Survey VCP Voluntary Cleanup Program VOC volatile organic compounds February 2014 vi Stockton East Water District

9 1.0 INTRODUCTION This Preliminary Feasibility Study technical memorandum (TM) summarizes results of the North Site pilot-scale recharge testing on farmland (known as the Bozzano property) located just north of the Stockton East Water District s (SEWD) Dr. Joe Waidhofer Water Treatment Plant (DJWWTP) to determine its suitability as a groundwater recharge and extraction site. The pilot-scale recharge testing is part of the North Site Groundwater Banking Feasibility Study (Study) that is being conducted by SEWD as part of the Water Bank Business Plan (Plan), developed in March of The Plan aimed to evaluate the feasibility of acquiring the Bozzano property and implementing a groundwater recharge facility on this site (North Site). If feasible, the recharge facility would store surface water from the Stanislaus and Calaveras rivers and then be extracted to serve as an additional water supply during dry years, when deliveries from surface water supplies are limited. Pilot-scale recharge testing activities conducted at the North Site focused on two primary objectives: (1) collecting subsurface data to assess the nature, thickness, and permeability of the unsaturated or vadose zone in the area, and (2) collecting complete pilot-scale recharge testing data to estimate percolation rates and recharge performance. 1.1 SITE DESCRIPTION The North Site, shown in Figure 1-1, is located north of East Main Street, approximately two miles east of Highway 99 and the City of Stockton, in San Joaquin County, California. The North Site is bordered by the Stockton Diverting Canal (SDC) to the west, SEWD property to the south, and agricultural orchards to the north and east. The proposed recharge facility would consist of 265 acres, including the 230 acre Bozzano property and 35 acres of land already owned by SEWD. Since 1989, the site has been used for agricultural purposes. Primary crops include corn, asparagus and tomatoes. The site is owned by Richard Bozzano and encompasses two assessors parcels (APN and ). Stockton East Water District 1-1 February 2014

10 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project Figure 1-1. Groundwater Recharge Program Site Area Map February Stockton East Water District

11 1.0 Introduction 1.2 PILOT-SCALE RECHARGE TESTING The pilot-scale recharge testing conducted and described in this preliminary feasibility technical memorandum used the Farmington Groundwater Recharge Program, Program Manual (Program Manual) (USACE, 2004) as a guide for assessing the feasibility of the site for recharge operations. As described in the Program Manual, pilot-scale recharge testing is the second stage of a four-stage process to objectively evaluate a site for its groundwater recharge potential (USACE, 2004). Data collected and evaluated during each of the first three stages are used to support a decision about whether a site will advance to the fourth and final stage, be archived for evaluation at a future time, or be eliminated from further consideration for artificial groundwater recharge. If a site advances successfully through the first three stages, it is fine-tuned in the fourth stage for long-term, maximum artificial groundwater recharge performance. The four stages are briefly described below, including information on the status of the North Site: 1. Initial Site Screening The goal of Stage 1 is to make an initial, low-cost assessment of whether a site could be suitable for artificial groundwater recharge, and whether additional evaluations should be made. Noninvasive methods are used to acquire readily available data (e.g., site visits, literature search) for each site. If no significant conditions are identified that would likely impede or preclude artificial groundwater recharge, the site is advanced to Stage 2. Initial site screening was completed for the North Site and is described in Section Field Investigation The goal of Stage 2 is to evaluate whether a site could be suitable for artificial groundwater recharge through the application of minimally invasive, sitespecific field investigation activities (e.g., subsurface exploration and pilot-scale recharge testing). If results suggest that development of artificial groundwater recharge facilities may be possible, the site is advanced to Stage 3, with the consent of the landowner. Initial field investigations were conducted in 2011, as described in the Report of Managed Aquifer Recharge (SoundEarth Strategies, 2011a) and the Addendum to October 6, 2011 Report of Managed Aquifer Recharge (SoundEarth Strategies, 2011b). This TM summarizes results of Stage 2 activities at the North Site and provides a recommendation regarding whether the site should be advanced to the next stage of evaluation. 3. Demonstration-Scale Recharge Testing The goal of Stage 3 is to determine if a site is suitable for long-term artificial groundwater recharge through designing and constructing full-scale recharge facilities and executing a performance test for 6 months to 3 years. Performance testing is designed to evaluate recharge effectiveness, aquifer response, and site maintenance requirements. If results indicate that long-term use of the site (up to 4 years) for artificial groundwater recharge is viable, the site will advance to Stage 4, with landowner consent. 4. Long-Term Operation and Maintenance The goal of Stage 4 is to develop and implement best management practices (BMP) for maximizing groundwater recharge over the intended life of the site. BMPs will be based on general industry practices and sitespecific information, including some of the performance and monitoring data collected during Stage 3. Stockton East Water District 1-3 February 2014

12 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project Success of the recharge operations depends on the methodical application of this staged approach, which was designed to minimize costs by screening out likely unfavorable sites during Stages 1 and 2, which involve relatively inexpensive, non-invasive, or minimally invasive activities, before proceeding to more costly and time-consuming site work associated with Stages 3 and 4. Therefore, choosing to move a site forward from Stage 2 to Stage 3 represents an important economic decision. Should the Final Groundwater Banking Feasibility Study Report conclude that the site is feasible for recharge operations, it would be recommended that SEWD follow through with demonstration testing (Stage 3) prior to long-term implementation. 1.3 ORGANIZATION OF THIS TECHNICAL MEMORANDUM This TM is organized as follows: 1. Chapter 1, Introduction provides background information about groundwater recharge in eastern San Joaquin County, presents background on the North Site including a brief site description, discusses pilot-scale recharge testing, and describes the organization of the TM. 2. Chapter 2, Summary of Preliminary Activities presents a summary of the first phase of pilot-scale recharge testing at the North Site, including preliminary activities such as initial screening and preparatory activities for the site. 3. Chapter 3, Summary of Previous Field Investigations presents a summary of the previous field investigations completed on the North Site and neighboring properties. 4. Chapter 4, Pre-pilot scale recharge test field activities and monitoring presents the results of monitoring well drilling, initial groundwater elevation monitoring, and initial groundwater quality testing conducted before initiation of pilot-scale recharge testing. 5. Chapter 5, Design, Location, and Construction of Pilot-Scale Recharge Test presents a summary of the design, location, and construction of the pilot-scale recharge tests after review and analysis of previous field investigations. 6. Chapter 6, Pilot-scale recharge testing results and analysis presents the results of pilotscale recharge testing and analysis at the North Site. 7. Chapter 7, Conclusions - summarizes knowledge gained from the results of field investigations and technical analyses. 8. Chapter 8, Summary summarizes in a series of tables the pilot-scale recharge testing activities at the North Site in terms of ranking criteria outlined in the Farmington Groundwater Recharge Program Manual (USACE, 2004b). 9. Chapter 9, Recommendations presents recommendations regarding the suitability of the North Site for artificial groundwater recharge and what recharge techniques should be implemented. 10. Chapter 10, References contains sources used to prepare this TM. February Stockton East Water District

13 2.0 SUMMARY OF PRELIMINARY ACTIVITIES The first phase of pilot-scale recharge testing at the North Site encompassed a series of preliminary activities including initial site screening, a Pilot-Scale Field Recharge Plan, a Phase I Environmental Site Assessment (ESA), a Draft Initial Study (IS) and Negative Declaration (ND) (SEWD, 2013), obtaining permits, completing underground service alert markings, and developing a health and safety plan. The Phase I ESA and document preparation was performed in April In addition, a Draft IS and ND was prepared in January 2013 by SEWD, although this particular document is not typically prepared as part of pilot-scale recharge testing. These assessments were a continuance of initial screening of the site, but conducted in more detail, to identify any obvious concerns before more costly site work began. Necessary permits and information on the presence of underground utilities were obtained before subsurface exploration or pilot-scale recharge testing commenced. These preliminary site activities at the North Site are described in more detail in the following sections. 2.1 INITIAL SITE SCREENING ACTIVITIES Initial landowner coordination took place to assess landowner willingness to participate in the pilot-scale recharge testing to evaluate general site feasibility, and identify the presence of any significant conditions at or near the site that would likely impede or preclude artificial groundwater recharge. Initial site screening also included review of existing studies conducted at the North Site and neighboring properties. Reports reviewed for this study were completed by SoundEarth Strategies (2011a, 2011b), previous recharge testing and aquifer testing from the neighboring SEWD Northwest Site (former 35-Acre site) (MWH, 2006a and 2006b), U.S. Geological Survey (USGS) testing of and installation of STK7, a multi-completion monitoring well (see Appendix A), the Farmington Groundwater Recharge Program Manual (Program Manual) (USACE, 2004b), historical groundwater levels at neighboring wells, boring and well logs from existing borings and wells in the vicinity of the site. These reports were reviewed to identify potential soil and water quality concerns, develop conceptual model of subsurface deposits and geologic features, determine the nature of surficial soils, develop an understanding of historical groundwater elevation data, potential water sources and conveyance structures, historical land use, accessibility, existing structures, and utilities and underground improvements. 2.2 PILOT-SCALE RECHARGE TESTING PREPARATORY ACTIVITIES Prior to pilot-scale recharge testing at the North Site, a Pilot-Scale Field Recharge Plan (Appendix B) was developed that documented the recommendations for pilot-scale recharge testing including testing locations, testing methods, and monitoring activities. Stockton East Water District 2-1 February 2014

14 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project 2.3 PHASE I ENVIRONMENTAL SITE ASSESSMENT A Phase I ESA, which is a limited environmental investigation, was conducted for the site in April 2013 in accordance with American Society for Testing and Materials (ASTM) standards (ASTM, 2000a, and ASTM, 2000b). The purpose of the ESA was to review past and current land uses and activities at the site to assess the possible presence of hazardous substances, including hazardous wastes that could prohibit implementing pilot-scale recharge testing activities. The Phase I ESA and associated appendices is available in Appendix C. The ESA included a limited reconnaissance of the site and site vicinity; correspondence with agency contacts; and review of historical aerial photographs and historical topographic maps. The ESA also evaluated if any past or current land use activities could influence pilot-scale recharge testing activities. This was accomplished through review of a database of regulatory agency files by Environmental Data Resources (EDR) to find regulatory enforcement actions, permits, or investigations into hazardous materials or wastes associated with the site to identify any recognized environmental conditions (REC) (EDR, 2005). The ASTM standard for a Phase I ESA (ASTM E ) (2000a) defines a REC as follows: The presence or likely presence of any hazardous substances or petroleum products on a property under conditions that indicate an existing release, a past release, or a material threat of a release of any hazardous substances or petroleum products into structures on the property or into the ground, groundwater or surface water of the property. The term includes hazardous substances or petroleum products even under conditions in compliance with laws. The term is not intended to include de minimis conditions that generally do not present a material risk of harm to public health or the environment and that generally would not be the subject of an enforcement action if brought to the attention of appropriate governmental agencies. As documented in the Phase I Environmental Site Assessment, North Site (Bozzano Site), report (Appendix C), no RECs were observed at the North Site that would preclude groundwater recharge testing activities. One Voluntary Cleanup Program (VCP) property, located within ½ mile of the North Site, was identified. However, this site is not likely to pose a REC for the recharge site because the site is at a lower elevation than the target property, the contamination was localized and impacted only surficial soils (no impact to groundwater), and the site is down gradient of the target property and is undergoing mitigation through a cleanup program. Recommendations of the ESA included gathering background groundwater quality data, monitoring groundwater levels at neighboring wells to evaluate the influence of recharge on adjacent properties, and further investigating the VCP property located within ½ mile of the North Site before implementing demonstration testing of the North Site. 2.4 INITIAL STUDY AND NEGATIVE DECLARATION A Draft Initial Study (IS) and Negative Declaration (ND) was prepared by SEWD as the California Environmental Quality Act (CEQA) Lead Agency (SEWD, 2013). A ND has been prepared concurrently with this IS to meet the requirements of CEQA. The purpose of the IS/ND are to disclose the environmental effects of groundwater recharge testing at the North Site. The February Stockton East Water District

15 2.0 Summary of Preliminary Activities IS/ND focus on environmental effects caused by the demonstration-level or full-scale recharge test and identifies best management practices (BMP) that would reduce environmental effects to a less-than-significant level. The Final ND and Notice of Determination (NOD) were certified in March PERMITS After the site was approved for pilot-scale recharge testing activities, it was determined that three monitoring wells would be drilled for subsurface soil exploration and constructed. Drilling and well construction permits were obtained from the San Joaquin County Environmental Health Department (SJCEHD) before drilling activities commenced. SJCEHD was onsite to inspect the grouting procedures for the monitoring well. Inspections were performed to ensure that no open conduit to groundwater was present. Copies of the SJCEHD permits are included in Appendix D. 2.6 UNDERGROUND SERVICE ALERT Underground Service Alert (USA) was contacted before the monitoring wells were drilled. Areas containing USA markings and/or markings provided by SEWD staff were avoided during work activities. 2.7 PILOT-SCALE RECHARGE TESTING WATER SOURCE A 14,000 gallon tank was placed at the perimeter of the North Site and was plumbed into the Bozzano property main irrigation line for the purposes of pilot-scale recharge testing. The tank was fed with water from SEWD s North pond which receives water from both New Melones and New Hogan via Peters and Bellota pipelines. Water from the North pond, fed by both New Melones and New Hogan water will be the long-term supply for full-scale implementation of the project. 2.8 SUMMARY OF FINDINGS OF PRELIMINARY ACTIVITIES Following are findings from preliminary activities at the North Site: 1. Based on the Phase I ESA, no evidence was found of prior industrial or other activities that would preclude pilot-scale testing recharge activities at the North Site (Appendix C). 2. No mitigation measures were identified in the ND as necessary for implementation of the recharge project. 3. Long-term source water for full-scale recharge testing is available from the North pond located just due south of the North Site. Stockton East Water District 2-3 February 2014

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17 3.0 SUMMARY OF PREVIOUS FIELD INVESTIGATIONS The second phase of pilot-scale recharge testing at the North Site included characterizing subsurface conditions at the site. This was accomplished by reviewing previous studies conducted on the North site, as well as collecting soil lithologic data, groundwater elevation, and groundwater quality data. Data obtained from previous studies was used to guide pilot-scale recharge test design and location. These studies are described in more detail below AQUIFER TEST AT EVALUATION The goal of the aquifer test evaluation conducted at the SEWD site in 2006 was to better define the aquifer properties. The results of the aquifer test showed that 2 of the 9 wells monitored during the test period exhibited definitive groundwater level responses to aquifer testing. The lack of responses from other wells, inferred the presence of a heterogeneous subsurface and the possible presence of a local confining unit. The results enabled the calculation of transmissivity, storativity, and horizontal hydraulic conductivity, as presented in Table 3-1. Table 3-1. Results of Aquifer Test Evaluation Aquifer Parameter Calculated Value Transmissivity ft 2 /min Storativity Hydraulic Conductivity (horizontal) ft/min (3-23 ft/day) Key: ft/day = feet per day ft/min = feet per minute ft 2 /min = feet squared per minute PILOT SCALE RECHARGE TESTS AT THE FORMER 35-ACRE SITE Two groundwater recharge pilot tests were conducted in 2006 on the former 35-Acre Site, which is located south of, and adjacent to, the North Site (Figure 1-1). These pilot tests evaluated two recharge techniques - flooded field and spreading basin. The flooded field technique consisted of applying water to a bermed field, while the spreading basin technique consisted of excavating the recharge area to a depth of 5 feet and applying water to the excavated area. The flooded field technique (although less expensive to construct) presented several drawbacks, including lower percolation rates (average equivalent to 0.36 feet per day [ft/day]) and seepage through the constructed berms which resulted in uncertainty regarding the actual percolation rate (USACE, 2006b). The flooded field technique yielded a higher recharge rate (average equivalent to 0.62 ft/day) with none of the nuisance seepage issues. The average recharge rates from these tests as well as long-term rates collected from the SEWD 60-Acre recharge facility and Guelph permeameter tests at the North Site are presented in Table 3-2. The approximate locations where these measurements were taken are presented in Figure 3-1. Stockton East Water District 3-1 February 2014

18 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project Table 3-2. Results of Guelph Permeameter Testing, Pilot-Scale Recharge Testing, and Demonstration Testing in Vicinity of North Site Estimated Percolation Name Rate (ft/day) Guelph Permeameter Tests BP BP BP BP BP01 2 NA Pilot-Scale & Demonstration Scale Recharge Tests East Pond (60-Acre Site) 0.7 North Pond (60-Acre Site) 0.2 South Pond (60-Acre Site) 0.5 Flooded Field (former 35-Acre Site) 0.36 Spreading Basin (former 35-Acre Site) 0.62 Notes: 1 Location deferred and ultimately abandoned following release of large quantity of water into boreholes. 2 Testing begun on August 11, 2011, no drop in water level was observed for 1.25 hours, test terminated. Key: ft/day = feet per day February Stockton East Water District

19 3.0 Summary of Previous Field Investigations Stockton East Water District 3-3 February 2014 Figure 3-1. Locations of Guelph Permeameter Testing, Monitoring Wells, Production Wells, Pilot-Scale Recharge Testing, and Demonstration Testing in Vicinity of North Site

20 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project FIELD INVESTIGATIONS AT THE NORTH SITE Field investigations conducted in 2011 estimated percolation rates at 4 locations along the North Site boundary using a Guelph permeameter (SoundEarth Strategies, 2011a and 2011b). Results of these tests, which measure percolation rates on a small scale, were used to estimate the portions of the site with the highest and lowest potential percolation rates. The only Guelph permeameter test location that yielded an percolation rate in the acceptable range for long-term recharge operation (assumed to be at least 0.2 ft/day based on the Program Manual USACE, 2004), was along the western site boundary (percolation rate equivalent to 0.23 ft/day). In addition to estimating percolation rates at multiple sites, the field investigations conducted in 2011 included drilling four borings around the perimeter of the North Site. The boring information was then reviewed with other existing boring and well log information to develop a sediment texture model of the subsurface. February Stockton East Water District

21 4.0 PRE-PILOT-SCALE RECHARGE TEST FIELD ACTIVITIES AND MONITORING The following section describes field activities completed prior to initiating the pilot-scale recharge test at the East and West recharge basins. These activities included monitoring well drilling, completion, and development, water quality sampling from the monitoring wells and source water, and initial groundwater elevation monitoring. 4.1 MONITORING WELL DRILLING, COMPLETION, AND DEVELOPMENT To evaluate subsurface soil conditions at the North Site, boreholes were drilled in the locations of the three proposed monitoring wells between March 11 and March 13, One borehole was drilled just east of the western-most basin, one just west of the eastern-most basin, and one approximately halfway between the two basins, as shown in Figure 1-1. Borehole drilling services were provided by a subcontracted drilling company (Cascade Drilling, Inc.). Drilling was performed using the hollow stem auger (HSA) technique. Each well was drilled to approximately 73 feet below ground surface (bgs). During well drilling, soil samples were collected continuously using a split-spoon sampler. Lithologic logging was performed using the Unified Soil Classification System (USCS). The field lithologic logs and photos of split-spoon samples are provided in Appendices F and G. Once lithologic logging was completed, monitoring wells were installed to collect groundwater quality and groundwater elevation data at the North Site. Monitoring well casings, well screens, filter pack sand, and well seals were installed by the driller immediately after drilling ended, as shown in Figure 4-1. Well screen intervals were selected based on observation of soil type, depth to first groundwater, and expected seasonal water table fluctuations. The monitoring wells were constructed with 2-inch diameter PVC screens and casings. The diagram in Figure 4-1 shows a typical well completion diagram for all three monitoring wells. Figure 4-2 presents a cross-section of the subsurface strata across the North Site. Stockton East Water District 4-1 February 2014

22 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project Figure 4-1. Monitoring Well Completion Diagram February Stockton East Water District

23 4.0 Pre-Pilot-Scale Recharge Test Field Activities and Monitoring Figure 4-2. Cross-Section from A-A Across the North Site Stockton East Water District 4-3 February 2014

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25 4.0 Pre-Pilot-Scale Recharge Test Field Activities and Monitoring Following completion of the monitoring wells, the wells were developed by purging at least three well casing volumes of water using the driller s bailing and pumping techniques. This was performed to flush fine sediments from the filter pack surrounding the well screen. A copy of the completion well reports and well development information forms are provided in Appendix E Lithologic Data As mentioned, lithologic data was collected during drilling of the monitoring well boreholes. An on-site field geologist under the direct supervision of a California Registered Geologist described the samples during lithologic logging in accordance with the United Soil Classification System or USCS (ASTM, 2000c, and ASTM, 2000d). Appendix F contains lithologic logs filled out for the boreholes. Borehole lithology is described below. Table 4-1 shows the borehole lithologic data logged at the site (see Appendix F for complete lithologic logs). Appendix G presents a photo log of split spoon samples collected during drilling. Lithologic data was collected with continuous cored sampling. Blow count data was also collected from the monitoring wells using a standard test method (ASTM, 1999). Blow counts are a method of penetration-testing soils with a split barrel sampling tool on the drill rig. The number of hits or blow counts created by a hammer of standard weight and height, dropped from a standard distance on the sampler at a specific depth, was recorded over a 0.5-foot depth. Stockton East Water District 4-5 February 2014

26 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project Monitoring Well ID MW-NS-01 MW-NS-02 MW-NS-03 Sample Depth (feet bgs) Table 4-1. Borehole Lithologic Data Blow Counts Density/ Consistency USCS stiff OH Organic Clayey Silt /9/9 stiff ML/MH Silt/Elastic Silt /9 very stiff ML Silt /8 very stiff ML/MH Silt/Elastic Silt /8/8 stiff ML Silt /7/7 stiff ML/MH Silt/Elastic Silt /9/8 stiff ML Silt /9/9 stiff ML/MH Silt/Elastic Silt /9/10 stiff ML Silt stiff SM Silty Sand /9/9 stiff ML Silt /11/9 medium dense SM Silty Sand /10/10 very stiff ML/MH Silt/Elastic Silt /12/8 medium dense SM Silty Sand /6/9 loose SW Well-Graded Sand medium stiff OH Organic Clayey Silt soft to medium stiff ML Silt /7/7 stiff to very stiff ML Silt /8/8 very stiff ML/MH Silt/Elastic Silt /11/7 very stiff ML Silt /9/10 very stiff ML/MH Silt/Elastic Silt very stiff ML Silt /8/9 very stiff ML/MH Silt/Elastic Silt /11/13 very stiff ML Silt stiff OH Organic Clayey Silt /9/11 stiff to very stiff ML/OH Silt/Organic Clayey Silt /9/9 stiff to very stiff ML/MH Silt/Elastic Silt /9/6 stiff to very stiff ML Silt stiff GM Silty Gravel stiff to very stiff ML Silt /7/8 loose GM Silty Gravel /9 stiff ML Silt /10 medium dense GM Silty Gravel /9/10 very stiff ML/MH Silt/Elastic Silt /11/7 very stiff ML Silt /8/6 stiff to very stiff ML/MH Silt/Elastic Silt Key: bgs = below ground surface USCS = Unified Soil Classification System The counts required to penetrate soil correspond to a stiffness qualitative value, as specified in the USCS and shown for each borehole in Table 4-1. For increments greater than 1.5 feet (corresponding to 3 blow counts), only the first 3 blow counts are shown. February Stockton East Water District

27 4.0 Pre-Pilot-Scale Recharge Test Field Activities and Monitoring Based on analysis of the lithologic data collected during monitoring well drilling, the vast majority of soils encountered from ground surface to a depth of approximately 40 consisted of silt, although some interbeds of sand and silty gravel are also present. The density of the silt was generally stiff to very stiff, while the sands and gravels were medium dense or loose (generally good for infiltration) Grain Size Analysis Grain size analysis was performed on one soil sample from each of the three borehole locations in the screen interval below the groundwater surface. Soil samples were submitted to a subcontracted soils laboratory for grain size analysis. Table 4-2 summarizes the results of the grain size analysis; the complete grain size analysis report is provided in Appendix H. Monitoring Well ID MW-NS MW-NS MW-NS Key: bgs = below ground surface ID = identification Lt = light mm = millimeters wt = weight Table 4-2. Grain Size Analysis of Samples Collected from Boreholes Median Particle Size Distribution, wt. percent Depth ASTM Soil Grain (feet Sand Size Classification Size bgs) Gravel Silt Clay (mm) Coarse Medium Fine Lt. Brownish- Gray Sand with Clay (SP-SC) Lt. Brown Clay (CL) Lt. Brown Silty Sand (SM) Silt & Clay According to the grain size analysis data, the finest soils encountered were generally clay while the coarsest soils were medium sands in the screen interval zones sampled. Generally, the grain size analyses confirm the observations of the on-site geologist (Table 4-1). 4.2 WATER QUALITY SAMPLING Water quality samples were collected from groundwater in each of the monitoring wells and the source water feeding the East Recharge Basin (this source water also fed the West Recharge Basin). These samples were sent to a subcontracted certified analytical laboratory for analysis. The following sections describe results for each sample in further detail. Appendix I contains the complete analytical reports and a summary of water quality data for the samples, including maximum contaminant levels (MCL) for constituents based on California Department of Health Services (DHS) limits, unless otherwise specified. Stockton East Water District 4-7 February 2014

28 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project Monitoring Wells The monitoring well samples were collected on March 25 and March 26, 2013, to establish the baseline water quality of the groundwater at the North Site. Baseline groundwater quality data was collected to ensure that groundwater recharge at this site would not cause the migration of any known constituents of concern (COC). Based on laboratory analysis (Appendix I), no volatile organic compounds (VOC), chlorinated herbicides, organochlorine pesticides, polychlorinated biphenyls (PCB) pesticides, or fecal coliform were reported above their respective detection limits in the baseline groundwater sample collected from the monitoring wells. Total Dissolved Solids (TDS) measurements for all three wells were also above the U.S. Environmental Protection Agency s (EPA) Secondary Drinking Water Standard of 500 mg/l. In MW-NS-01 and MW-NS-03, nitrate levels exceeded the State and federal MCLs. Total coliform measurements from MW-NS-01 also exceeded the MCL. A summary of all detected constituents is provided in Table 4-3. As discussed in Section 4.1, the monitoring well was screened in the first hydrogeologic zone encountered during drilling (42-72 ); therefore, reported groundwater quality represents shallow groundwater near the top of the saturated zone. February Stockton East Water District

29 4.0 Pre-Pilot-Scale Recharge Test Field Activities and Monitoring Stockton East Water District 4-9 February Constituent Units Table 4-3. Summary of Baseline Water Quality Constituents Detected Groundwater Quality Monitoring Well MW-NS01 (3/25/13) Groundwater Quality Monitoring Well MW-NS02 (3/26/13) Groundwater Quality Monitoring Well MW-NS03 (3/25/13) Source Water East Pond (4/3/13) Total Alkalinity mg/l Bicarbonate as CaCO3 mg/l Carbonate as CaCO3 mg/l ND ND ND ND Hydroxide as CaCO3 mg/l ND ND ND ND Chloride mg/l Specific Conductance (EC) µmhos/cm , Hexavalent Chromium µg/l ND 10 2 Total Hardness as CaCO3 mg/l Nitrate as N mg/l ND 10 Nitrite as N mg/l ND ND ND ND 1 ph ph units Sodium Adsorption Ratio sqrt(meq/l) Sulfate as SO4 mg/l Total Dissolved Solids mg/l Arsenic µg/l ND 10 Boron µg/l ND Calcium µg/l 75,000 62, ,000 5,800 Copper µg/l ND ND ND ND 1300 Iron µg/l ND ND ND Magnesium µg/l 39,000 32,000 51,000 2,300 Manganese µg/l ND ND ND ND 50 1 Potassium µg/l , ND Sodium µg/l 75,000 90,000 75,000 2,800 MCL

30 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project February Stockton East Water District Constituent Units Table 4-3. Summary of Baseline Water Quality Constituents Detected (contd.) Groundwater Quality Monitoring Well MW-NS01 (3/25/13) Groundwater Quality Monitoring Well MW-NS02 (3/26/13) Groundwater Quality Monitoring Well MW-NS03 (3/25/13) Source Water East Pond (4/3/13) Zinc µg/l ND ND ND ND 5,000 1 Total Coliforms MPN/100mL <1.8 > Fecal Coliforms MPN/100mL <1.8 <1.8 < Total Trihalomethanes (THM) µg/l ND 0.59 ND Notes: 1 Secondary Standard 2 California Department of Public Health Maximum Contaminant Level Bold text indicates exceedence of Federal MCL Key: µg/l - micrograms per liter µmhos/cm - micro Siemens per centimeter MCL - maximum contaminant level mg/l - milligrams per liter MPN - most probable number ND - none detected MCL

31 4.0 Pre-Pilot-Scale Recharge Test Field Activities and Monitoring Source Water A baseline water quality sample was taken from the source water entering the East Pond to verify that the water would not contaminate the aquifer through recharge. Based on laboratory analysis (Appendix I), no VOCs, chlorinated herbicides, organochlorine pesticides and PCBs, pesticides, or nitrogen/phosphorus were reported above their respective detection limits in a sample collected on April 3, 2013, except where noted below. Total and Fecal coliform were reported at most probable number (MPN) concentrations of >1,600 and 11, respectively, which exceeded State and federal MCLs. The coliform values are not considered problematic because of the relatively thick unsaturated zone which will effectively remove these constituents from the source water before it reaches the saturated zone. 4.3 GROUNDWATER ELEVATION MONITORING Groundwater elevations were first monitored in the newly installed wells on April 2, At that time, groundwater levels were approximately 54 in MW-NS-01, 60 in MW- NS-02, and 59 in MW-NS-03. Stockton East Water District 4-11 February 2014

32 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project This page left blank intentionally. February Stockton East Water District

33 5.0 DESIGN, LOCATION, AND CONSTRUCTION OF PILOT- SCALE RECHARGE TEST This section describes the design, location, and construction of the spreading basin recharge facilities at the SEWD North site, including preparatory and construction activities. SEWD staff constructed and installed all of the temporary equipment necessary for pilot-scale recharge testing. Data collected from 2011 field investigations, pilot-scale recharge testing at the former 35-Acre site in 2006 (USACE, 2006b), and aquifer testing completed in 2006 (USACE, 2006a) were evaluated to establish the design and select locations for pilot-scale recharge testing at the site. Data collected from these studies included the following: 1. Borehole lithology, grain size analysis, blow count, and Guelph permeameter test data (SoundEarth Strategies, 2011a and 2011b) 2. Percolation rates, borehole lithology, grain size analysis, and blow counts (MWH, 2006b) 3. Aquifer properties including transmissivity, storativity, and hydraulic conductivity (MWH, 2006a) 5.1 RECOMMENDED RECHARGE TECHNIQUES FOR PILOT-SCALE RECHARGE TESTING The spreading basin recharge technique described in the Program Manual (USACE, 2004) was selected as the most appropriate method. This method involves excavating surface soil through low-permeability soils and/or shallow hardpan layers to depths of 2 to 5 feet. Borings from field investigations in 2011 (SoundEarth Strategies, 2011a) indicated the presence of a silty clay layer to a depth of 3 feet in the northeast corner of the perimeter (B0ALT1 boring), clayey silt to a depth of 10 feet (B03) in the southeast corner of the perimeter, clayey silt to a depth of 50 feet (B02) in the north central portion of the perimeter, clayey silt and organic clay to a depth of 33 feet (B01) in the northwest corner of the perimeter. In addition, previous pilot-scale recharge tests conducted at the former 35-Acre site indicated that the flooded field technique used at one of the test plots for this test was prone to seepage through sidewalls which made it difficult to estimate the actual percolation rate into the soil (USACE, 2006b). Based on a review of this data, it was recommended that two pilot-scale recharge spreading basins should be constructed at the site to observe the percolation rate of more permeable soils below the upper few feet of material. 5.2 SELECTION OF PILOT-SCALE RECHARGE TEST LOCATIONS Two recharge basins were constructed, one in the western portion of the North Site and one in the eastern portion of the site, as shown in Figure 1-1. These two areas were chosen for the recharge tests because they were considered to represent two potential end members (high and low) percolations rates, based on the existing data reviewed for the site. The goal of the pilotscale recharge test was to select locations that would be considered representative of the entire site, thus evaluating the potential high and low percolation rate areas was concluded to provide the most representative information for the entire site. Stockton East Water District 5-1 February 2014

34 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project 5.3 CONCEPTUAL PILOT-SCALE RECHARGE BASIN DESIGNS A preliminary analysis of the potential for groundwater mounding under the two pilot-scale recharge basins was conducted before finalizing the conceptual pilot-scale recharge basin designs. The groundwater mounding analysis was completed using the Hantush equation (see Carleton, G. B., 2010) and a readily available tool produced by the USGS (USGS, 2012). Input data used for these calculations included recharge rate, specific yield, horizontal hydraulic conductivity, recharge basin length and width, duration of the infiltration period, and an initial thickness of the saturated zone (to the first confining or semi-confining unit). The sources for the data used to make initial groundwater mounding estimates were obtained from the following sources: Average recharge rates from the pilot-scale testing at the former 35-Acre site (USACE, 2006b) Specific yield values from California s Groundwater: Bulletin 118 (DWR, 2003) Horizontal hydraulic conductivity from aquifer testing at the SEWD site (USACE, 2006a) Initial thickness of the saturated zone was estimated from a review of well logs and geophysical logs in the vicinity of the site (see Appendix A) To maximize the potential for mounding that would be observed at monitoring wells, recharge basin length and width and the duration of infiltration period were varied. Based on the results of this analysis, a conceptual pilot-scale recharge basin size was recommended, as presented in the Pilot-Scale Field Recharge Plan (Appendix B). An estimate of the volume of water required for testing was based on the Guelph permeameter tests (SoundEarth Strategies, 2011a and 2011b) and pilot-scale recharge tests at the former 35- Acre site (USACE, 2006b). Conceptual designs of both recharge tests are included in Appendix J. 5.4 SPREADING BASIN CONSTRUCTION AND ACTIVITIES This section discusses how the two test sites were constructed, and describes instrumentation that was installed, site measures observed, and conveyance used for delivering source water to the test plots Spreading Basins Recharging groundwater using spreading basins consists of applying water to an excavated basin created for this purpose; allowing for percolation of the water through the bottom and side walls of the excavation, as shown conceptually in Figure 5-1. The locations of the spreading basins at the SEWD North site are illustrated in Figure 1-1. The locations for these spreading basins were finalized after discussion with the SEWD, as described in Section 4. Before initiating construction of the spreading basins, SEWD staff measured and staked out the locations of the pilot-scale recharge test basins according to the conceptual designs. Both spreading basins were approximately 100 feet by 100 feet and were excavated to a February Stockton East Water District

35 5.0 Design, Location, and Construction of Pilot-Scale Recharge Test depth of approximately 3 feet deep with an excavator and backhoe (see Figure 5-1). Heavy plastic sheeting was draped over the berms and on the vertical sidewalls of the spreading basins to protect from sloughing caused by wave erosion and to prevent excavated soils from blowing into the basins. During the entire test period, the plastic sheeting on the sidewalls remained intact. Figure 5-1. Conceptual Drawing of Spreading Basin Note: Spreading Basin test plots at the North Site. A) Spreading Basin outlet, showing source water conveyance piping in foreground. B) Spreading Basin East Pond. Figure 5-2. Spreading Basins at North Site Water Source, Conveyance, and Measuring Devices Water was conveyed to both spreading basins for the purpose of pilot-scale recharge testing. The source water was obtained from SEWD s north holding pond, and consisted of a mix of water from the Calaveras and Stanislaus rivers. This water is currently the surface water that is purchased by the lease of the Bozzano property. The source water was pumped into a large tank Stockton East Water District 5-3 February 2014

36 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project daily which was attached to the irrigation main line on the Bozzano property. Existing irrigation pipelines on the site routed the water from the main line to the two different spreading basins at different turn-outs. SEWD coordinated with the lease holder to verify the feasibility of use of the pipelines for the duration of the recharge test Water Source Water used for pilot-scale recharge testing at both test plots was pumped from SEWD s north holding ponds located at the SEWD site. Surface water originating from the Stanislaus River is stored in the holding ponds prior to being treated and delivered by SEWD Conveyance Pipelines Source water was conveyed from the holding pond to the recharge test plots through the Bozzano property main irrigation line and irrigation pipelines. A PVC Tee was installed along the pipeline to deliver water to the spreading basin. A ball valve was installed at each spreading basin to control the flow rate of source water into each plot during refilling. The discharge piping located within each test plot was a section of pipe installed upwards to prevent erosion and washout of the test plot bottom Measuring Devices Staff gauges were installed in each spreading basin to monitor pond depths during testing. The bottom, or zero reading, on each staff gauge was located at the base of the spreading basin. The pond depth in each spreading basin was typically measured and recorded on its respective staff gauge once per day (excluding weekends). A description of the methodology used to calculate percolation rates with the use of staff gauge data is provided in Section Site Safety The recharge basins were located within the Bozzano property, north of the SEWD facility grounds, but accessible through the SEWD facility. The SEWD grounds are enclosed by an 8- foot chain-link fence and are further protected by security and surveillance cameras. There was no opportunity for the public to access the spreading basins through the SEWD property. Public access to the spreading basins would be limited to access through private farm roads. February Stockton East Water District

37 6.0 PILOT-SCALE RECHARGE TESTING RESULTS AND ANALYSIS This chapter describes North Site pilot-scale recharge testing activities and results and decommissioning of pilot-scale testing facilities at the site. As described above, the second phase of pilot-scale recharge testing at the North Site included characterizing subsurface conditions at the site. Previous field investigations at or near the site provided a basis for designing the recharge basins. However, data collected in conjunction with pilot-scale recharge testing were used to further characterize the site to identify its potential for groundwater recharge. 6.1 PILOT-SCALE RECHARGE TESTING DATA Various quantitative data were collected during pilot-scale recharge testing at the North Site. Source water field parameters (ph, electrical conductivity, turbidity, and temperature) and water depth within the recharge test plots were measured along with evaporation and precipitation data to determine final percolation rates. SEWD staff visited the site nearly every day to record test plot water depth, to refill the test plots to a depth between 1 and 3 feet, and to periodically measure the field parameters. Qualitative data for site conditions also were collected to determine whether algae and/or abundant suspended solids were evident. These data are described and analyzed in the following sections Pilot-Scale Recharge Test Source Water Field Parameters Physical characteristics (field parameters) of water used for pilot-scale recharge testing were measured to ensure that the source water did not negatively affect recharge performance. Source water at the North Site was pumped from SEWD s North holding pond to the black storage tank distributing water to the North Site (Bozzano property) irrigation line. The source water was monitored during pilot-scale recharge testing according to the Pilot-Scale Field Recharge Plan (Appendix B) for the four field parameters listed in Table 6-1. Source water was sampled and analyzed on a weekly basis throughout the duration of the recharge test. Data in Table 6-1 show that source water used for pilot-scale recharge testing at the North Site had low turbidity and no other parameters that could potentially affect recharge testing results, like high total dissolved solids (TDS). Stockton East Water District 6-1 February 2014

38 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project February Stockton East Water District West Pond East Pond Table 6-1. Source Water Field Parameters Constituent Units 04/03/13 04/10/13 04/17/13 04/24/13 05/02/13 05/07/13 05/15/13 05/16/13 Turbidity NTUs NA Conductivity µs/cm NA Temperature C NA TDS ppm NA 1 NA 1 NA NA ph ph units NA Turbidity NTUs NA NA 1.43 Conductivity µs/cm NA NA 173 Temperature C NA NA 20.6 TDS ppm NA NA 1 NA NA 87.0 ph ph units NA NA 8.27 Notes: 1 Field sensor did not have capability to measure TDS Key: C = degrees Celsius µs/cm = micro Siemens per centimeter NA = not available NTU = nephelometric turbidity units ppm = parts per million TDS = total dissolved solids

39 6.0 Pilot-Scale Recharge Testing Results and Analysis Spreading Basin Water Depths SEWD personnel measured and recorded the water depths in each test plot on a daily basis during the 6 week testing period. Water depth measurements were recorded from the staff gauges installed in each test plot, accurate to 0.01 feet Groundwater Depth Data Groundwater depth data was collected from the three monitoring wells (MW-NS-01, MW-NS- 02, and MW-NS-03) throughout the duration of the recharge testing. Groundwater depths were also measured at 17 other wells, including three triple-nested monitoring wells (MW-1A through 1C, MW-2A through 2C, and MW-3A through 3C) that SEWD monitors monthly. In addition, groundwater depth data for four USGS wells in the area was obtained on the USGS Web page. The wells monitored during pilot-scale recharge testing are shown in Figure 6-1. Stockton East Water District 6-3 February 2014

40 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project Figure 6-1. Groundwater Depth Monitoring February Stockton East Water District

41 6.0 Pilot-Scale Recharge Testing Results and Analysis Groundwater Quality Data Groundwater quality data was collected from the three monitoring wells near the end of the recharge test. This data was then compared to the baseline data collected at the start of the test to determine if recharging the aquifer using surface water would have any negative impacts on the groundwater quality in the area. Groundwater quality data was also collected from two wells, SEWD production well and Bozzano shed, near the pilot-scale recharge tests that were screened at deeper depth intervals (see Appendix A for well logs). The locations of the wells from which groundwater quality samples were obtained are illustrated in Figure Microscopic Particulate Analysis In addition to groundwater quality testing at SEWD production well 74-01, a microscopic particulate analysis (MPA) was conducted to address the question of whether groundwater was under the influence of surface water during recharge testing. The SEWD Business Plan proposes using existing production wells, such as production well for extraction as part of the implementation of the banking program. The MPA test was conducted to determine whether the pilot-scale recharge test and other existing SEWD recharge operations at the 60-acre site have influenced groundwater at the depth of the production well well screen interval ( ) such that the signature of surface water is detected in the groundwater quality. The MPA test was conducted at the end of the pilot-scale recharge test period in accordance with testing protocol (see Appendix K). Water from production well was routed from a sampling port off the pump and plumbed through tubing to the MPA apparatus, as illustrated in Figure 6-3. Approximately 1,000 gallons of water was plumbed through the MPA apparatus at a rate between 1 and 1.5 gallons per minute. The water was discharged to the ground surface near the pump house. The remaining water pumped from production well during this test was fed through the existing SEWD facilities to an onsite reservoir. Stockton East Water District 6-5 February 2014

42 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project Figure 6-2. Groundwater Quality Monitoring February Stockton East Water District

43 6.0 Pilot-Scale Recharge Testing Results and Analysis Figure 6-3. Microscopic Particulate Analysis Apparatus Evaporation and Precipitation Evaporation and precipitation were monitored to obtain accurate volume measurements of recharged water. Evaporation and precipitation data were downloaded daily from the California Irrigation Management Information System (CIMIS) database and Web page. To obtain more representatives measurements, the data from two nearby stations, No. 70 near Manteca and No. 167 near Tracy, were averaged. Data from the nearest CIMIS station, No. 166 near the City of Lodi was not available during the testing period. The CIMIS station reports precipitation and reference evapotranspiration (ETo), which was converted for the pilot-scale recharge test to evaporation by multiplying by the correct monthly factor derived from data on the CIMIS Web page Site Conditions SEWD staff visited the site on a daily basis from April 2 to May 17, 2013, to monitor qualitative site conditions, including presence of vectors, algae, and suspended sediments Vector Control The recharge facilities were located approximately 1,400 feet and 1,650 feet from an SEWD north holding pond that contains water throughout much of the year. Therefore, the potential for recharge activities to increase the populations of mosquito and other water-borne vectors locally was not considered significant. As expected, SEWD staff did not observe any signs of vectors in or around the recharge test plots during routine site inspection activities Attractive Nuisances Due to the relatively remote location of the site, it is unlikely that testing activities and/or facilities were attractive nuisances. No complaints were received by adjacent landowners during testing. No evidence of trespassing or vandalism was observed during testing. Stockton East Water District 6-7 February 2014

44 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project 6.2 GROUNDWATER ELEVATIONS As mentioned, groundwater elevations were measured in the three monitoring wells and 17 other nearby wells on a weekly basis between April 2 and May 17, Groundwater elevation data was also downloaded weekly from the USGS Web site for 4 USGS wells. Figure 6-4 shows continuous measurements of the depth to water versus time collected with pressure transducers for monitoring wells MW-NS-01, MW-NS-02 and MW-NS-03. In MW-NS-01 and MW-NS-02, located next to the West Pond and East Pond, respectively, the groundwater elevations increased by approximately two feet over the course of the testing. The groundwater elevation in MW-NS- 03, which was not located immediately next to either recharge pond, increased by approximately a half foot over the course of the test. Post-test, the groundwater elevations in all three monitoring wells exhibited a slightly deeper depth than at the initiation of the test. This could indicate that the monitoring wells were influenced by neighboring agricultural pumping during the early irrigation season, which overlapped with the early testing period. 64 MW-NS-01_Transducer MW-NS-02 Transducer 62 MW-NS-03 Transducer 60 Depth to Water (feet) Figure 6-4. Depth to Water vs. Time for Monitoring Wells Depth to water data for the additional wells and the three monitoring wells on the North Site is presented in Figure 6-5. Most of the wells, with the exception of two of the USGS wells, experienced a decrease in groundwater elevation of less than 10 feet during the course of the test, likely due to the influence of groundwater pumping during the irrigation season. February Stockton East Water District

45 6.0 Pilot-Scale Recharge Testing Results and Analysis 100 Depth to Water (feet) A4 (pump house) MW 1A - west MW 1B - center MW 1C - east T1 (pump house) (pump station) (pump station) Bozzano MW 2A - north MW 2B - center MW 2C - south 60 acre PZ1 Cutter MW 3A - north MW 3B - center MW 3C - south USGS USGS USGS USGS MW-NS-01 MW-NS-02 MW-NS /2/2013 4/16/2013 4/30/2013 5/14/2013 5/28/2013 6/11/2013 Date Figure 6-5. Depth to Water vs. Time for SEWD Wells 6.3 GROUNDWATER QUALITY Groundwater quality samples were collected from monitoring wells MW-NS-01, MW-NS-02 and MW-NS-03 near the end of the test on May 15 and May 16, The results of this testing are presented in Table 6-2 below. In all three wells, the nitrate concentrations exceeded the State and Federal MCLs. In addition, TDS concentrations were above the U.S. EPA s Secondary Drinking Water Standards. In MW-NS-01, the iron concentration also exceeded the Secondary Drinking Water Standard set by the U.S. EPA. Stockton East Water District 6-9 February 2014

46 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project Constituent Table 6-2. Summary of Post-Test Water Quality Constituents Detected Units Groundwater Quality Monitoring Well MW-NS01 (5/16/13) Groundwater Quality Monitoring Well MW-NS02 (5/15/13) Groundwater Quality Monitoring Well MW-NS03 (5/16/13) Total Alkalinity mg/l Bicarbonate as CaCO3 mg/l Carbonate as CaCO3 mg/l ND ND ND Hydroxide as CaCO3 mg/l ND ND ND Chloride mg/l Specific Conductance (EC) µmhos/cm Hexavalent Chromium µg/l Total Hardness as CaCO3 mg/l Nitrate as N mg/l Nitrite as N mg/l ND ND ND 1 ph ph units Sodium Adsorption Ratio sqrt(meq/l) Sulfate as SO4 mg/l Total Dissolved Solids mg/l Arsenic µg/l Boron µg/l ND Calcium µg/l 8, ,000 96,000 Copper µg/l 17 ND ND 1300 Iron µg/l 530 ND Magnesium µg/l 36,000 43,000 48,000 Manganese µg/l ND ND ND 50 1 Potassium µg/l 6,200 4,800 6,800 Sodium µg/l 65,000 86,000 82,000 Zinc µg/l ND ND ND 5,000 1 Total Coliforms MPN/100mL 2 <1.8 <1.8 5 Fecal Coliforms MPN/100mL <1.8 <1.8 <1.8 5 Total Trihalomethanes (THM) µg/l ND ND ND 80 Notes: 1 Secondary Standard California Department of Public Health Maximum Contaminant Level Bold text indicates exceedance of Federal MCL Key: µg/l = micrograms per liter MCL = maximum contaminant level mg/l = milligrams per liter MPN = most probable number ND = none detected MCL February Stockton East Water District

47 6.0 Pilot-Scale Recharge Testing Results and Analysis Groundwater samples were also collected at SEWD production well 74-01, on May 16, 2013, and at the Bozzano shed well May 17, The results of the water quality testing are shown in Table 6-3. All of the detected constituents in these two wells were present at concentrations below the State and federal MCLs. Table 6-3. Summary of Post-Test Water Quality Constituents Detected at Neighboring Wells Constituent Units Groundwater Quality Groundwater Quality Bozzano MCL (5/16/13) Well (5/17/13) Total Alkalinity mg/l Bicarbonate as CaCO3 mg/l Carbonate as CaCO3 mg/l ND ND Hydroxide as CaCO3 mg/l ND ND Chloride mg/l Specific Conductance (EC) µmhos/cm Hexavalent Chromium µg/l ND ND 10 2 Total Hardness as CaCO3 mg/l Nitrate as N mg/l Nitrite as N mg/l ND ND 1 ph ph units Sodium Adsorption Ratio sqrt(meq/l) Sulfate as SO4 mg/l Total Dissolved Solids mg/l Arsenic µg/l Boron µg/l ND ND Calcium µg/l 26,000 19,000 Copper µg/l ND Iron µg/l ND ND Magnesium µg/l 13,000 12,000 Manganese µg/l ND ND 50 1 Potassium µg/l 6,800 7,400 Sodium µg/l 22,000 22,000 Zinc µg/l ND ND 5,000 1 Total Coliforms MPN/100mL <1.8 <1.8 5 Fecal Coliforms MPN/100mL <1.8 <1.8 5 Total Trihalomethanes (THM) µg/l Notes: Key: 1 Secondary Standard µg/l = micrograms per liter 2 California Department of Public Health Maximum MCL = maximum contaminant level Contaminant Level mg/l = milligrams per liter MPN = most probable number ND = none detected Stockton East Water District 6-11 February 2014

48 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project An MPA test was also conducted at production well to determine whether the groundwater at the site was under the influence of surface water. The results of the MPA test, which are summarized in Table 6-4, indicate groundwater is not under the influence of surface water. Table 6-4. Results of Microscopic Particulate Analysis Test Giardia Coccidia Other Algae Rotifers Cryptosporidium Diatoms Insect/Larvae Plant Debris Amorphous Debris Plant Pollen Crustacea Ciliates/Flagellates Minerals Nematodes Amoeba Bio-Indicator Other Organisms Key: NS = none seen TNTC = too numerous to count Primary Secondary Result NS NS NS NS NS NS NS NS TNTC NS NS NS TNTC NS NS NS 6.4 SPREADING BASIN RECHARGE PONDS The bases of the North Site recharge basins both measured approximately 100 by 100 feet. Water depth in the basins varied between 0.85 and 2.81 feet during recharge testing. (Section 5 contains a conceptual illustration of a spreading basin and photos of the actual spreading basins constructed at the North Site.) The following section discusses pond depth, percolation rate, and cumulative percolation volume data collected during pilot-scale recharge testing of the test ponds Pond Depth Pond depth in the test ponds was monitored by SEWD personnel on a near-daily basis between April 2 and May 17, Water in the ponds was maintained at depths ranging from 0.85 feet to 2.81 feet for the duration of testing. The ponds were refilled continuously by SEWD staff by pumping source water into them. Figure 6-6 illustrates the depth of water versus time for the test ponds. Recharge basin depth data was not available for the East Basin on May 12, February Stockton East Water District

49 6.0 Pilot-Scale Recharge Testing Results and Analysis Water Depth (feet) East Pond West Pond /2 4/7 4/12 4/17 4/22 4/27 5/2 5/7 5/12 5/17 Date Figure 6-6. Depth of Water vs. Time for Test Pond Recharge Test Percolation Rates Multiple variables were monitored to calculate percolation rates at the site, as listed below for the percolation rate equation. Water quantities necessary for pilot-scale recharge testing were estimated after reviewing previous studies and conducting an initial analysis. Evaporation and precipitation data were collected from the weather stations, as described above, and as mentioned, careful records of recharge basin water depths were collected during testing according to the Pilot-Scale Field Recharge Plan (Appendix B) to determine final percolation rates. A water balance was used to derive the percolation rate during direct pilot-scale recharge testing, as shown below. P = {(S1-S2) + P E}/T Where: P S2 = Percolation rate (feet per day) = Current depth of water in test site (feet) Stockton East Water District 6-13 February 2014

50 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project S1 P E T = Previous depth of water in test site (feet) = Precipitation (feet) = Evaporation (feet) = Time (days) Percolation rates were calculated using data collected from April 2 to May 17, For the West Pond, calculated percolation rates varied between 0.67 and 1.27 feet per day, with the average rate being approximately 0.93 feet per day. For the East Basin, percolation rates ranged between 0.32 and 0.59 feet per day, with an average rate of approximately 0.45 feet per day. Because water depth data was not available in the East Basin on May 12, the percolation rate for May 13 was averaged over a two-day period. Clogging due to vegetation, biological, or chemical influences did not appear to affect the performance of the pilot-scale recharge test of the spreading basin at the North Site, but these factors should be considered during longer duration testing. Figure 6-7 shows percolation versus time for the test ponds East Pond West Pond Precipitation (inches) Percolation Rate (feet/day) Average Percolation Rate = 0.93 feet per day 0.4 Average Percolation Rate = 0.45 feet per day /2 4/7 4/12 4/17 4/22 4/27 5/2 5/7 5/12 5/17 Date Figure 6-7. Percolation vs. Time for Test Pond Recharge Test February Stockton East Water District

51 6.0 Pilot-Scale Recharge Testing Results and Analysis Cumulative Percolation Volumes Cumulative percolation volumes were calculated from data collected between April 2 and May 17, The volume of water that percolated during this period was 9.87 acre-feet for the West Basin and 4.76 acre-feet for the East Basin. Figure 6-8 shows the cumulative volume of water percolated over time in each test pond. The trend remains relatively stable throughout the duration of testing, suggesting that significant clogging effects did not occur during the test period Cumulative Percolation Volume (acre-feet) East Pond West Pond 2 0 4/2 4/7 4/12 4/17 4/22 4/27 5/2 5/7 5/12 5/17 Figure 6-8. Cumulative Percolation Volume vs. Time for Test Pond Recharge Test Decommissioning of Pilot-Scale Recharge Test Facilities At the time this document was prepared, SEWD staff had not yet decommissioned the recharge testing facilities. 6.5 GROUNDWATER MOUNDING As described above in Section 4, initial estimates of groundwater mounding underneath each of the two spreading basins were calculated using the Hantush equation, in the USGS s Hantush Tool spreadsheet (USGS, 2012). Section 4 presents the sources from which estimates for the field parameters were obtained to make calculations for the North Site. After completion of the pilot-scale recharge tests, the tool was calibrated for the groundwater mounding observed at Date Stockton East Water District 6-15 February 2014

52 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project the North Site during field testing. The average recharge rates were updated for the two sites based on field data, while the horizontal hydraulic conductivity and specific yield were varied to best fit the conditions observed (mounding exhibited at the monitoring wells next to the respective recharge basins and in the central well). From the testing it could not be distinguished from which test the central well was influenced, so the results from the calculations consider that it was caused entirely by one or the other recharge basins. These calculations provide a range of horizontal hydraulic conductivities and specific yield values for the subsurface. The parameters estimated by these calculations are presented in Table 6-5 for the two recharge basins. Table 6-5. Hydraulic Properties Estimated from Pilot-Scale Recharge Testing Recharge Rate Test Time Specific Yield Horizontal Conductivity (ft/day) Test Size by by 100 Key: ft/day = feet per day February Stockton East Water District

53 7.0 CONCLUSIONS The following section summarizes the key findings from the pilot-scale recharge testing and analysis. 7.1 GROUNDWATER QUALITY As described in Section 4 and 6, groundwater quality was collected at the three monitoring wells installed for the project, MW-NS-01, MW-NS-02, and MW-NS-03 both pre- and post-test. Following the pilot-scale recharge test, the groundwater quality demonstrated elevated concentrations of nitrate, iron, and TDS. In all three wells, the nitrate concentrations exceeded the State and Federal MCLs. In addition, TDS concentrations were above the U.S. EPA s Secondary Drinking Water Standards. In MW-NS-01, the iron concentration also exceeded the Secondary Drinking Water Standard set by the U.S. EPA. These results suggest that the source of the elevated constituents was intercepted between the ground surface and the water table in the vadose zone. The elevated concentrations may be a temporary phenomenon, which would be resolved after enough water was flushed through the soil column. Deeper groundwater quality was tested at the Bozzano shed well, a well screened in a more intermediate zone ( ) and production well 74-01, screened in a deeper zone of the Laguna Formation ( ). All of the analyzed constituents in these two wells were present at concentrations below the State and Federal MCLs. The source water to be used for recharge at the site was tested at the beginning of the test as described in Section 4. Total and Fecal coliform were reported at MPN concentrations of >1,600 and 11, respectively, which exceeded State and federal MCLs. The coliform values are not considered problematic because of the relatively thick unsaturated zone which will effectively remove these constituents from the source water before it reaches the saturated zone. No issues related to the source water were identified that would be of concern for the banking program. Elevated nitrate and iron may be of potential concern for long-term operations. Elevated nitrate in the shallow groundwater is potentially associated with application of nitrate as part of agricultural practices in the region and may experience seasonal spikes in concentrations during the beginning of the irrigation season (as was the timing for the pilot-recharge test). If groundwater for the banking project was extracted from wells screened at the same zones as the Bozzano shed well ( ) or well ( ) it would not require blending to meet State and Federal drinking water quality standards. The groundwater quality of these wells did not exceed State or Federal MCLs. The SEWD plant would provide adequate treatment of extracted water from these wells. If groundwater were extracted from the shallow zone, as observed in monitoring wells MW-NS-01, MW-NS-02, and MW-NS-03, then this water would need to be blended with other groundwater from deeper zones before being blended with the raw water supply. A simple mixing calculation was completed to conclude that groundwater from the shallow zone would require blending with deeper water before blending with the raw water supply if Stockton East Water District 7-1 February 2014

54 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project constituents such as nitrate found in the shallow groundwater were persistent. The mixing equation is presented below. Concentration = (C 1 V 1 +C 2 V 2 ) / (V 1 +V 2 ) Where C 1 = concentration of nitrate in groundwater, C 2 = concentration of nitrate in raw surface water supply. V 1 = volume of groundwater V 2 = volume of raw surface water The results of the calculations, using nitrate concentrations observed during the post-test groundwater quality testing at monitoring wells MW-NS-01, MW-NS-02, and MW-NS-03 show that nitrate concentrations would exceed the MCL if 80 percent of the raw water consisted of groundwater pumped from the screen interval consistent with those wells. In general, it is concluded that water quality concerns can be managed through treatment and blending, and do not present a significant limitation to the feasibility of a future banking project. 7.2 PERCOLATION RATES The soils underlying the North Site consist of silty clays, silts, silty sands, and clay. The upper 100 to 200 is part of the Alluvium and Modesto/Riverbank Formation (DWR, 2003). As described in Section 7, the average percolation rates measured at the West Basin and East Basin were 0.93 ft/day and 0.45 ft/day, respectively. According to the ranking criteria presented in the Program Manual (USACE, 2004), the lower end of the range of estimated percolation rates (0.45 ft/day) would be considered moderately desirable in terms of the suitability of the geology and soil conditions. However, if it is assumed the actual percolation rate is somewhere in between the two average percolation rates from both basins (0.45 ft/day and 0.93 ft/day) then conditions may be considered more favorable. Although the Program Manual may indicate that percolation rates of 0.45 ft/day are moderately desirable, it should be noted that the conditions presented in the manual are more reflective of estimated percolation rates worldwide. Programs within the Central Valley of California have shown that infiltration rates less than 0.45 ft/day can result in successful groundwater recharge programs (e.g. Kern Water Bank with an estimated recharge rate of 0.3 ft/day). Therefore, for the purposes of this evaluation, the conditions at the North Site would indicate that the percolation rates are suitable for operating the site as a recharge facility. Using the best available information, calculations were made with the Hantush equation, described above in Section 4, to calculate the potential mounding at the recharge basin assuming the hydraulic parameters estimated in Section 6 and an approximate full-scale recharge basin (4,000 feet by 2,900 feet). The Surface Water Availability Analysis completed in conjunction with this evaluation indicated that surplus surface water may be available for groundwater recharge in more than 50 percent of the future years with annual recharge amounts peaking around 44,000 acre-feet/year at the 2020 level of demand, assuming an average recharge rate of 0.6 feet per day. The length of time for recharge was calculated as the annual recharge of 44,000 acre-feet divided by the recharge basin area (4,000 feet by 2,900 feet), multiplied by the February Stockton East Water District

55 7.0 Conclusions average recharge rate (volume/area multiplied by recharge rate). Two rates were used, representing the two pilot basins average rates, resulting in two end-member time periods. The length of time calculated for the West and East Basins were 179 days and 369 days (more than a year to recharge 44,000 acre-feet if recharge rate was 0.45 feet per day). The results of the calculations made using the Hantush equation indicate that using hydraulic parameters estimated for the West Basin and East Basin (average recharge rates of 0.93 ft/day and 0.45 ft/day, respectively), the recharge basin would experience nearly 400 feet of mounding at the center of the basin. Based on these calculations, it appears that groundwater mounding will limit the amount of water that could be applied to the North Site in a given year. The results from this analysis indicate that continuous operation and flooding of the entire North Site is likely unreasonable, but that different operation scenarios may be more appropriate for operating the basin successfully. Calculations made using the Hantush equation indicated that the groundwater table would reach within 5 to 10 feet of the surface at the center of the basin after 9 days assuming the parameters for the West Basin and 11 days assuming the parameters for the East Basin. This would indicate that storage beneath the basin would have filled with water. In order to store additional water, the water directly beneath the site would need to migrate horizontally away from the site to create more available storage capacity. Therefore, different operational scenarios would be critical to maintain a sustainable long-term recharge rate. These calculations used the best available information, which we believe are reasonable at this stage, but will need to be borne out by demonstration-scale testing. As described above, the estimated average recharge rate was 0.93 ft/day at the West Basin and 0.45 ft/day at the East Basin. The average recharge rate at the North Site and former 35-Acre site combined may decrease over time due to clogging, algae growth, or other causes. However, records from the SEWD 60-Acre site indicate that the average recharge rate has remained relatively constant since initiation of operation in Therefore, if comparable, the North Site may perform similarly. 7.3 GROUNDWATER LEVEL RESPONSE As described in Section 6 above, MW-NS-01 and MW-NS-02, located next to the West Pond and East Pond, respectively, the groundwater elevations increased by approximately two feet over the course of the pilot-recharge test. The groundwater elevation in MW-NS-03, which was not located immediately next to either recharge pond, increased by approximately a half foot over the course of the test. It is expected that the recharge water from North Site would primarily go to the shallow Alluvium and Modesto/Riverbank Formations which extend 100 to 200 feet bgs. The Laguna Formation underlies the Alluvium and Modesto/Riverbank Formations and extends from approximately 800-1,000 (DWR, 2003). The Plio-Pleistocene Laguna Formation consists of discontinuous lenses of stream-laid sand and silt with lesser amounts of clay and gravel (DWR, 2003). Because of the high level of stratification of the aquifer (clay and silt lenses interbedded with more permeable sand and some gravel), the recharge water is expected to primarily move horizontally as opposed to vertically downward after it intercepts the water table. To maximize production, the proposed extraction wells would be similar to the existing agricultural wells, and would likely be screened from approximately 100 feet to 300 feet depth in the lower Alluvium and Modesto/Riverbank Formations and upper Laguna Formation. Stockton East Water District 7-3 February 2014

56 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project The 2006 aquifer test evaluation, which involved pumping production well (screened in the Laguna Formation between 200 and 500 ) concluded that it was not possible to evaluate the potential for recovering recharged groundwater through pumping at SEWD because of the limited time period of the aquifer test (USACE, 2006a). The report concluded that the subsurface under SEWD contains layers of interconnected sands that serve as conduits between wells and as a result, groundwater level responses in nearby wells will likely vary according to what sand layers each well and the pumping well are screened through (USACE, 2006a). The information summarized above indicates that depending on the timing of storage and extraction, the majority of water extracted would be native groundwater from deeper zones (zones within screened interval), and not the groundwater recharged (assuming extraction well design similar to existing agricultural wells). The exact proportion of water that is from recharge or native sources will depend on the storage volume, storage time, and extraction timing. It is not unexpected that the water extracted as part of the North Site Groundwater Banking Project would be native groundwater because it would not be recommended for economic and physical reasons to build shallow wells that would only extract water recharged by the project. An advantage of extracting native groundwater rather than shallow recharged water as part of the North Site Groundwater Banking Project is that little or no treatment may be required of deeper groundwater. The profile of banked water beneath the North Site would consist of a mound that would develop under the site and have a lesser influence on groundwater levels with distance away from the center of the basin. General conclusions could be drawn from the preliminary calculations with the Hantush equation which indicate that the mound would be bell shaped with the peak at the center of the basin that declines at a shallow angle and then quickly drops off just beyond the extent of the basin. 7.4 DRAWDOWN The likely drawdown of recharged water for various drought scenarios would be dependent on a number of factors including, but not limited to, available surface water supply for irrigators who purchase water, potential changes in groundwater levels due to multiple year or single year dry periods and associated pump lift costs, pump efficiency, crop water demands, and distance of irrigation wells from the groundwater bank site. The potential drawdown of groundwater levels at the North Site due to pumping from the wells operated as part of the recharge program can be estimated by making some simplifying assumptions and using a simplified analytical approach. The analytical approach uses the Theis equation to evaluate concerns in a quantitative manner. The Theis equation assumes the well is within a confined system. This approach was selected because the results from aquifer test evaluation (USACE, 2006a) near the North Site indicate the presence of local semi-confined to confined system. The Theis equation is provided below. Theis Equation s = QW(u) 4πT February Stockton East Water District

57 7.0 Conclusions U = r2 S 4Tt Where s = drawdown (feet) Q = discharge (pumping) rate of the well (gpm) u = dimensionless time parameter T = transmissivity of the aquifer (ft 2 /min) r = distance from the pumping well to the point where drawdown is observed (feet) S = storativity (unitless) t = time since pumping began (minutes) W(u) = the well function The SEWD Business Plan indicates that the North Site Groundwater Banking Project would be operated on an 8 year cycle, which assumes 5 years of recharge at 26,500 acre-feet per year, and three years of extraction at 27,000 acre-feet per year. Calculations were completed to test the worst case scenario, in which SEWD would recharge 26,500 acre-feet and then immediately need to extract 27,000 acre-feet, yielding a net reduction in storage of 500 acre-feet per year. The following simplifying assumptions were made to calculate the potential drawdown at the North Site under the worst case scenario and estimate the area that would potentially be affected by a decline in groundwater levels from extraction operations at the site: Annual recharge (from SEWD Business Plan) = 26,500 acre-feet per year Annual extraction (from SEWD Business Plan) = 27,000 acre-feet per year Maximum extraction rate (from SEWD Business Plan, accounts for all 11 wells) = 36,600,000 gallons per day or 25,417 gallons per minute Confined aquifer (Theis equation applies) Hydraulic parameters from the SEWD aquifer test evaluation performed in 2006 (USACE, 2006a) (parameters presented in Table 3-1) The analysis presented above with regards to the percolation rate evaluates the hydraulic limitations of the site to recharge potential peak annual recharge amount of 44,000 acre-feet. The evaluation of drawdown presented here considers an estimate of what would be recharged in a given year, as presented in the SEWD Business Plan (26,500 acre-feet per year). Although calculations presented in this section were for an unlikely worst case scenario, SEWD does not Stockton East Water District 7-5 February 2014

58 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project anticipate that the North Site Groundwater Banking Project would be operated under this condition. A series of calculations were made to estimate the maximum drawdown at the nearest irrigation well and the radial distance away from the site that would experience declines in groundwater levels. These calculations assume that pumping is occurring at the 11 wells presented in Figure 7-1, including 7 new wells conceptually shown in the figure as located around the North Site for extraction purposes. The location of the wells presented in Figure 7-1 could potentially be re-located to a more appropriate location, such as along the Peters Pipeline. However, the location of these wells will be further evaluated at a future planning phase of the North Site Groundwater Banking Project. Table 7-1 presents the results from calculating the Theis equation assuming that the annual pumped volume would be 500 acre-feet and that the discharge rates would vary between 754 gallons per minute (equivalent to a 150 day pumping period) to the maximum proposed rate of 25,417 gallons per minute (4.5 day pumping period). The potential drawdown observed at the nearest pumping well was estimated by assuming that the 11 extraction wells (spatial location conceptually shown in Figure 7-1) would extract all 500 acre-feet of water. An important assumption here is that the water table would rise due to the recharge of 26,500 acre-feet of water, and the net withdrawal effect of extracting 27,000 acre-feet of water would be equivalent to extraction of 500 acre-feet of groundwater. This assumes that the recharged water would not be kept in storage for a long dormant period which could allow the groundwater mound to dissipate. February Stockton East Water District

59 7.0 Conclusions Stockton East Water District 7-7 February 2014 Figure 7-1. Conceptual Locations of Seven New Extraction Wells and Existing Extraction Wells on or Near the North Site

60 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project Table 7-1 presents the results from these calculations. Pumping from SEWD Site (gallons per minute) Change in Storage (acre-feet) Table 7-1. Results from Theis Equation Calculation Drawdown Extraction, Less than Change in Days 0.10 feet Storage Pumping (feet away (gallons) from site) Drawdown Less than 0.10 feet (miles away from site) Drawdown at the Nearest Irrigation Well 1 25, ,925, , , ,925, , ,925, , Notes 1 Location of nearest irrigation well based on visual inspection of aerial imagery. For the purposes of the Theis calculations, areas with less than 0.10 feet of groundwater level decline were considered to have negligible impacts. The results from these calculations show that the nearest irrigation well to the North Site could potentially experience up to 68 feet of drawdown under a short (4.5 days), more intense pumping period. The calculations show that if the pumping period extended 5 months (as shown in multiple years of the Surface Water Availability Analysis), then the nearest irrigation well to the North Site could potentially experience 2 feet of drawdown. Drawdown of 68 feet at the nearest irrigation well could potentially cause challenges for the well owner. Annual variations of 10 to 20 feet in groundwater levels is not unusual in the region during irrigation season, as observed from well hydrographs available through Department of Water Resources (DWR) CASGEM website. However, the measurements reported are likely not taken when the wells are pumping and may not reflect the pumping conditions at the wells. The results of the calculations also indicate that as expected, for a confined system the longer the period of pumping (lower pumping rate needed to recover the same volume of water), the greater the radial distance away from the well the aquifer will be impacted. However, the greater the pumping rate (shorter duration) the less radial area that will be impacted. February Stockton East Water District

61 8.0 SUMMARY This section summarizes pilot-scale recharge testing activities at the North site in terms of Stage 2 ranking criteria outlined in the Farmington Groundwater Recharge Manual (USACE, 2004). 8.1 GEOLOGY AND SOILS Two data types described below were used to evaluate the site geology and soils for the purpose of groundwater recharge: soil permeability and depth and thickness of the surface layer. Table 8-1 describes the data types and explains how soil samples were analyzed. Data Type Soil Permeability Depth and Thickness of Surface Surface Layer Data Source/Data Gathering Technique Guelph permeameter tests Pilot-scale recharge testing, spreading basin Lithologic logging Grain size analysis Key: bgs = below ground surface Table 8-1. Geology and Soils Desirable Conditions? Yes No X X X X Explanation Guelph permeameter tests were completed at three locations: BP-10, BP-02, and BP-02 (SoundEarth Strategies, 2011a and b). The highest initial percolation rate was observed in soil boring BP-10 of 0.23 ft/day. However, this would be considered moderately desirable in reference to the Program Manual (USACE, 2004). The other tests yielded results that would be considered least desirable using the same criteria (USACE, 2004). Data from two pilot-scale spreading basin recharge tests indicated that average percolation rates may vary between approximately 0.45 and 0.93 feet per day at the North Site. This range of values is not meant to suggest that the percolation rate will fluctuate over time (although that is possible); instead it represents the average calculated percolation rates observed at the two test sites based upon test data. The lower end of the range of estimated percolation rates (0.45 feet) would be considered moderately desirable, however assuming the actual percolation rate is somewhere in between 0.45 and 0.93 feet per day then conditions may be considered most favorable (USACE, 2004). Based on the soil borings, clays generally predominate from approximately 3 to the ground surface. Below 3, silts and clayey silty soils are generally more prevalent. No significant hardpan and/or clay layer was observed to exist throughout the entire site. Laboratory grain size analysis of soil samples in the screened zone indicated the presence of clay in MW-NS- 02. However, no continuous clay layer appears to be observed across the site that would prohibit infiltration from the surface. Stockton East Water District 8-1 February 2014

62 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project 8.2 LAND USE Two data types described in Table 8-2 were used to evaluate the SEWD North site land use for the purpose of groundwater recharge: possible contamination and adjacent land use concerns. Data Type Data Source/Data Gathering Technique Site inspections visual observations Table 8-2. Land Use Desirable Conditions? Yes No X Explanation No evidence of recognized environmental conditions (REC) was observed at the site. Possible Contamination Verbal communication X The landowner has no knowledge of any existing RECs. Environmental Site Assessment (ESA) X No regulatory agency files related to hazardous waste were found for this site. Site inspections visual observations X No evidence of RECs was observed immediately adjacent to the site. Adjacent Land Use Concerns Verbal communication ESA X X The landowner has no knowledge of any existing RECs immediately adjacent to the site. No regulatory agency files related to hazardous waste were found for properties immediately adjacent to the site. The Phase I ESA did identify a VCP site within 0.5 miles of the site that should be further investigated prior to demonstration testing. February Stockton East Water District

63 8.0 Summary 8.3 SOURCE WATER The three data types described in Table 8-3 were used to evaluate SEWD North site source water for the purpose of groundwater recharge: surface water availability, quality, and proximity and capacity. Data Type Surface Water Availability Surface Water Quality Surface Water Proximity and Capacity Data Source/Data Gathering Technique Observations Analytical laboratory analysis Observations Estimations Table 8-3. Source Water Desirable Conditions? Yes Key: µg/l = micrograms per liter DHS = California Department of Health Services mg/l = milligrams per liter MPN = most probable number SDC = Stockton Diverting Canal VOC= volatile organic compound X X X X No Explanation It is understood that surface water in the north holding pond, from the Calaveras and Stanislaus rivers is available for groundwater recharge year round. A surface water availability analysis completed as Task 1 of the North Site Groundwater Banking Feasibility Study addresses this question. Based on laboratory analysis, no VOCs, chlorinated herbicides, organochlorine pesticides and PCBs, pesticides, or nitrogen/phosphorus were reported above their respective detection limits in a sample collected on April 3, 2013, from the East Pond water source. Total and Fecal coliform was reported at most probable number (MPN) concentrations of greater than 1,600 and 11, respectively. As described above, a surface water availability analysis completed as Task 1 of the North Site Groundwater Banking Feasibility Study addresses this question. As described above, a surface water availability analysis completed as Task 1 of the North Site Groundwater Banking Feasibility Study addresses this question. Stockton East Water District 8-3 February 2014

64 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project 8.4 GROUNDWATER CONDITIONS Two data types described in Table 8-4 were used to evaluate groundwater conditions at the SEWD North site for the purpose of groundwater recharge: groundwater elevations and groundwater quality. Data Type Groundwater Elevations Groundwater Quality Key: bgs = below ground surface Data Source/Data Gathering Technique Monitoring well water level measurements Monitoring well analytical laboratory analysis Table 8-4. Groundwater Conditions Desirable Conditions? Yes No X X Explanation Groundwater elevation data were collected in March 2013 from the MW-NS-01, MW-NS-02, and MW-NS-03 wells installed as part of the project testing. At that time, depth to groundwater ranged from approximately As this was prior to the start of the irrigation season, the data collected prior to initiation of the recharge test did not suggest that groundwater elevations were being influenced by pumping occurring nearby. Depth to groundwater data was collected during recharge testing at the three monitoring wells. Based on laboratory analysis, no volatile organic compounds (VOC), chlorinated herbicides, organochlorine pesticides, or polychlorinated biphenyls (PCB) pesticides were reported above their respective detection limits in the baseline groundwater samples collected from the MW-NS- 01, MW-NS-02, or MW-NS-03 monitoring wells. Constituents that were detected and worth noting include: Nitrate as N exceeding the Federal MCL in all three monitoring wells post-test and total iron at concentration 5.3 mg/l in MW-NS-01 post-test. Nitrate was the only constituent found at concentrations exceeding Federal and State maximum contaminant levels (MCL). February Stockton East Water District

65 8.0 Summary 8.5 HABITAT ISSUES Three data types described in Table 8-5 were used to evaluate the existence of any habitat issues at the SEWD North site for the purpose of groundwater recharge: proximity to known habitat areas, development of unsolicited habitat, and existence of threatened and endangered species in source water. Data Type Proximity to Known Habitat Areas Data Source/Data Gathering Technique Site visits Negative Declaration Development of Unsolicited Site visits Habitat Key: ND = none detected SEWD = Stockton East Water District Table 8-5. Habitat Issues Desirable Conditions? Yes No X X X Explanation Refer to SEWD, 2012 for more information regarding conclusions with regards to habitat issues. Refer to SEWD, 2012 for more information regarding conclusions with regards to habitat issues. Refer to SEWD, 2012 for more information regarding conclusions with regards to habitat issues. Stockton East Water District 8-5 February 2014

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67 9.0 RECOMMENDATIONS This section contains recommendations regarding the next steps for consideration in the development of a groundwater bank at the North Site and existing SEWD facilities for recharge. Recommendations are based on evaluation of data collected during pilot-scale recharge testing and general considerations for groundwater banking programs across California. Further evaluation should be performed to estimate the approximate, long-term potential recharge rate of the 60-acre site, the 35-acre site (individually), and the cumulative project including the North Site, 60-acre site, and the 35-acre site in consideration of potential mounding effects that may limit recharge rates. Further evaluation should be performed to estimate the drawdown from existing SEWD extraction wells for a demonstration test given different extraction scenarios provided by SEWD (given locations of wells, pumping rates, and duration of pumping). Drawdown estimates should be made for the nearest adjacent production wells and sites with ongoing remediation activities including the Marley Cooling Towers site to the southeast and the VCP site identified in the Phase I ESA (approximately 0.5 miles east of the project area). Significant fluctuation in the groundwater elevation and/or gradient has the potential to affect remediation activities either in an adverse or positive manner. Complete demonstration testing at the 60-acre site, including documentation of data collected during the multi-year demonstration recharge testing of the facility by SEWD, and performing an extraction cycle at SEWD production wells and to test the potential drawdown to nearby wells under a banking scenario. Analysis of the data collected during the extraction cycle could then be used to verify analytical estimates of drawdown or improve on those estimates using field data. Conduct demonstration testing at the 35-acre site following recommendations presented in the Program Manual (USACE, 2004). The demonstration testing would further test the long-term recharge rates of the 35-acre site and would follow the suggested 6-month to 3 year length. Demonstration testing would include drilling one or two monitoring wells (depending on the availability/accessibility of the monitoring well MW-NW-1), water quality testing, and construction of the 35-acre facility to be consistent with the recommended final basin design. Collection of subsequent groundwater quality data from the shallow screened zone is recommended to evaluate whether nitrate concentrations persist above the State and Federal MCLs or if the data collected during recharge testing was a temporary phenomenon. This testing will help to improve recommendations for operational strategies under implementation of the groundwater bank. Development of a groundwater model would allow further quantification of the potential for recharge operations at the North Site to influence or be influenced by nearby contamination sites. Because of the limitations of generalized analytical equations, it is understood that the analytical modeling tools recommended for initial estimates of Stockton East Water District 9-1 February 2014

68 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project mounding and drawdown listed above are reconnaissance-level only. The impacts of multiple pumping scenarios, estimations of vertical groundwater flow, regional groundwater flow conditions, and simultaneous operation of multiple recharge basins is best evaluated using finite element or finite difference (numerical) groundwater modeling. It is recommended to develop a semi-regional groundwater flow model that will provide higher confidence of the impact of a proposed full-scale project. The groundwater flow model would be developed after demonstration-scale testing described above is complete so that new information on subsurface conditions can be incorporated in the numerical model. A groundwater model could potentially be used to do some simplified particle tracking to resolve any concerns about these sites. The groundwater model would also be useful in planning scenarios for operation of the groundwater bank. February Stockton East Water District

69 10.0 REFERENCES American Society for Testing and Materials (ASTM) Standard Test Method for Penetration Test and Split-Barrel Sampling of Soils. ASTM D ASTM. 2000a. Standard Practice for Environmental Site Assessments: Phase 1 Environmental Site Assessment Process. ASTM E ASTM. 2000b. Standard Practice for Environmental Site Assessments: Transaction Screen Process. ASTM E ASTM. 2000c. Unified Soil Classification System. ASTM D ASTM. 2000d. Unified Soil Classification System. ASTM D California Department of Water Resources (DWR) California s Groundwater, Bulletin 118 Update. Carleton, G. B Simulation of groundwater mounding beneath hypothetical stormwater infiltration basins: U.S. Geological Survey Scientific Investigations Report , 64 p. Environmental Data Resources, Inc. (EDR) The EDR Radius Map with Geocheck, 6700 E. Cooperopolis Road. Inquiry Number February 12. SoundEarth Strategies. 2011a. Report of Managed Aquifer Recharge, Characterization and Site Assessment for the Bozzano Property (Also known as the North Site in the Farmington Groundwater Recharge Program), Stockton, CA. September. SoundEarth Strategies. 2011b. Addendum to the Report of Managed Aquifer Recharge, Characterization and Site Assessment for the Bozzano Property, Stockton, CA. October. Stockton East Water District (SEWD) Calaveras River Integrated Stormwater Management Project Initial Study and Proposed Negative Declaration. USACE. 2004b. Farmington Groundwater Recharge Program Final Program Manual. Prepared by MWH. USACE. 2006a. Farmington Groundwater Recharge Program Final Aquifer Test Evaluation. Prepared by MWH. June. USACE. 2006b. Farmington Groundwater Recharge Program Final Technical Memorandum, Results of Pilot-Scale Recharge Testing, Stockton East Water District Northwest Site. Prepared by MWH. September. USGS Hantush USGS SIR xlsm tool. Available at: Stockton East Water District 10-1 February 2014

70 Final Preliminary Feasibility Study Technical Memorandum North Site Groundwater Banking Project This page left blank intentionally. February Stockton East Water District

71 mwhglobal.com 3321 Power Inn Road, Suite 300 Sacramento, California TEL FAX

72 Appendix A Data From Neighboring Wells

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108 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/09/2011 Farmland G. Moore 08/10/2011 BORING LOG Site Address: B01 Water Depth At Time of Drilling: Water Depth After Completion: Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description 15 Same as above, moist. 100 MH 20 Same as above, moist. Note: Root fibers, lenses of organic material, slightly darker and more odorous than the rest of the SILT. 100 MH 25 Boring paused at Boring resumed at 0804 on 08/10/2011. Clayey SILT (MH), dark brown (7.5 YR 3/2), moist. 100 MH (Note: organic-rich layer 2-3 inches thick at top of sample core, may be cave-in material.) 30 Clayey SILT (MH), dark brown (7.5 YR 3/4). 100 MH Note: Clay content decreasing with depth. Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube 98.6 lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 2 of 6

109 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/09/2011 Farmland G. Moore 08/10/2011 BORING LOG Site Address: B01 Water Depth At Time of Drilling: Water Depth After Completion: Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description Silty SAND (SM), fine grain. 50 SM 35 Silty SAND (SM), fine grained sand grading into a medium grain sand with gravel, color grades with increasing depth from dark brown (7.5 YR 3/4) to brown (7.5 YR 4/4), moist. 80 SM 40 MH Clayey SILT (MH), brown (7.5 YR 3/4), dilatancy slow, dry strength low, toughness low. Silty SAND (SM), brown (7.5 YR 4/4), fine grain, moist. SM Clayey SILT (MH), brown (7.5 YR 4/4), moist. 70 MH 45 Silty SAND (SM), medium grain, moist. 60 SM Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube 98.6 lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 3 of 6

110 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/09/2011 Farmland G. Moore 08/10/2011 BORING LOG Site Address: B01 Water Depth At Time of Drilling: Water Depth After Completion: Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description 50 Silty SAND (SM), medium to coarse grain, with fine to medium gravel, well graded, moist to wet. 70 SM 55 Same as above. 100 SM 60 Silty SAND (SM), coarse grain, trace to no gravel. 80 SM 1-2 inch clayey SILT (MH) lense, moist at 64.5 feet. 65 Same as above, no gravel. Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube 98.6 lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 4 of 6

111 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/09/2011 Farmland G. Moore 08/10/2011 BORING LOG Site Address: B01 Water Depth At Time of Drilling: Water Depth After Completion: Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description 50 SM 70 MH Clayey SILT (MH), brown (7.5 YR 4/4). Same as above, moist. 100 MH 75 Same as above. 100 MH 80 Same as above. 100 MH Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube 98.6 lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 5 of 6

112 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/09/2011 Farmland G. Moore 08/10/2011 BORING LOG Site Address: B01 Water Depth At Time of Drilling: Water Depth After Completion: Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description 85 Same as above. 100 MH 90 Same as above. Note: Drill /auger working hard under increased formation resistance to drilling. 100 MH 95 Same as above, moist to wet. MH 36 50/2 Change to 2-inch-diameter split spoon.clayey SILT (MH), brown (7.5 YR 3/3), dilatancy slow to none, dry strength slow, toughness low to none, very dense. 100 Refusal at 98.6 feet. Standard Penetration Test by ASTM D1586 (140 lb hammer) Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube 98.6 lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 6 of 6

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114 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/09/2011 Farmland G. Moore 08/09/2011 BORING LOG Site Address: B02 Water Depth At Time of Drilling: Water Depth After Completion: Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description 15 Same as above. Some white precipitate "banding", hydrochloric acid (HCL) reaction is strong. 100 MH 20 Same as above with white precipitate "banding" present. 100 MH 25 Same as above, no white precipitate visible. 100 MH 30 Same as above, dry Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube 78.0 lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 2 of 5

115 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/09/2011 Farmland G. Moore 08/09/2011 BORING LOG Site Address: B02 Water Depth At Time of Drilling: Water Depth After Completion: Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description 100 MH 35 Clayey SILT (MH), yellowish brown (10 YR, 5/4) with gray clay clasts below, dry 100 MH 40 Same as above, dry. Note: Auger turning at increased rate, heating casing, soil cutting steaming. (increased formation resistance to drilling). 100 MH 45 Same as above. MH Note: Sampler (steel split spoon) very hot to touch. 50 Silty SAND (SM), fine grain, dense to very dense. Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube 78.0 lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 3 of 5

116 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/09/2011 Farmland G. Moore 08/09/2011 BORING LOG Site Address: B02 Water Depth At Time of Drilling: Water Depth After Completion: Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description SM 50 Same as above. 50 SM 55 Silty SAND (SM), reddish, well graded, with trace gravel. 50 SM MH Clayey SILT (MH) grades to fine to coarse grain sand, very dense, wet. Silty SAND (SM), reddish, well graded, with trace gravel. SM 60 Silty SAND (SM), reddish, medium to coarse grained, with gravel, wet. 60 SM 65 Same as above. Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube 78.0 lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 4 of 5

117 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/09/2011 Farmland G. Moore 08/09/2011 BORING LOG Site Address: B02 Water Depth At Time of Drilling: Water Depth After Completion: Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description 60 SM 70 Silty SAND (SM) to silty GRAVEL (GM), medium to coarse grained sand, with 40% to 50% gravel, medium to coarse grained. 60 SM-GM 75 Clayey SILT (MH), brown (7.5 YR 4/4) dilatancy slow to none, dry strength low, toughness low to none, very dense. MH Note: Augers turning at high rate (increased formation resistance). Refusal at 78.0 feet. Bottom of boring at 78.0 feet. 80 Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube 78.0 lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 5 of 5

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119 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/11/2011 Farmland G. Moore 08/11/2011 BORING LOG Site Address: B03 Water Depth At Time of Drilling: Water Depth After Completion: Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description 15 Same as above. 100 MH 20 Same as above. 100 MH 25 Same as above, moist to wet. 100 MH 30 with sand (sand fraction approximately 30%) Same as above. Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube 61.5 lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 2 of 4

120 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/11/2011 Farmland G. Moore 08/11/2011 BORING LOG Site Address: B03 Water Depth At Time of Drilling: Water Depth After Completion: Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description 100 MH 35 Same as above, no sand. 100 MH 40 Same as above. 100 MH with medium to coarse gravel 45 Same as above, with sand and trace gravel. 100 MH Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube 61.5 lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 3 of 4

121 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/11/2011 Farmland G. Moore 08/11/2011 BORING LOG Site Address: B03 Water Depth At Time of Drilling: Water Depth After Completion: Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description 50 Same as above. 100 MH 55 Same as above, decreasing gravel content. 100 MH /3 MH Same as above, very dense. Refusal at 61.5 feet. Standard Penetration Test by ASTM D1586. (140 lb hammer) Bottom of boring at 61.5 feet. 65 Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube 61.5 lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 4 of 4

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123 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/08/2011 Farmland G. Moore 08/08/2011 BORING LOG Site Address: Water Depth At Time of Drilling: Water Depth After Completion: B03ALT1 Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description MH Same as above. White precipitate at 17 ft, hydrochloric acid (HCL) reaction none MH Same as above, no white precipitate MH Same as above. CL Silty CLAY (CL), dark grayish brown (10 YR 4/2), dilatancy slow, dry strength medium, toughness medium, moist CL Same as above. Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 2 of 7

124 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/08/2011 Farmland G. Moore 08/08/2011 BORING LOG Site Address: Water Depth At Time of Drilling: Water Depth After Completion: B03ALT1 Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description B03ALT CL Sample collected at 34 feet, Same as above. MH Clayey SILT (MH), brown (10 YR 4/3), moist MH Same as above MH Same as above. Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 3 of 7

125 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/08/2011 Farmland G. Moore 08/08/2011 BORING LOG Site Address: Water Depth At Time of Drilling: Water Depth After Completion: B03ALT1 Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description MH Same as above, but less clay MH Same as above. with fine sand MH Same as above SW SAND (SW), fine to coarse grained, little gravel, wet. Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 4 of 7

126 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/08/2011 Farmland G. Moore 08/08/2011 BORING LOG Site Address: Water Depth At Time of Drilling: Water Depth After Completion: B03ALT1 Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description B03ALT Sample collected at 69.5 feet, MH Clayey SILT (MH), dark yellowish brown (10 YR 4/4), dilatancy none to slow, dry strength low, toughness low, moist MH Same as above. White precipitate, hydrochloric acid (HCL) reaction strong MH Same as above, no white precipitate but with trace gravel grading into sand. Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 5 of 7

127 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/08/2011 Farmland G. Moore 08/08/2011 BORING LOG Site Address: Water Depth At Time of Drilling: Water Depth After Completion: B03ALT1 Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description MH Same as above MH Same as above MH Same as above. 100 Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 6 of 7

128 Project: Project Number: Logged by: Date Started: Surface Conditions: Well Location N/S: Well Location E/W: Reviewed by: Date Completed: MAR SI "North Site" (Bozanno Properties) S G. Moore /B. Copeland 08/08/2011 Farmland G. Moore 08/08/2011 BORING LOG Site Address: Water Depth At Time of Drilling: Water Depth After Completion: B03ALT1 Stockton, California San Joaquin County APN acres Depth () Interval Blow Count % Recovery Sample ID USCS Class Graphic Lithologic Description 100 MH Same as above, very dense. Refusal at feet. Bottom of boring at feet Drilling Co./Driller: Drilling Equipment: Sampler Type: Hammer Type/Weight: Total Boring Depth: Total Well Depth: State Well ID No.: Precision Sampling CME 75 Continuous Sample Tube lbs Well/Auger Diameter: Well Screened Interval: Screen Slot Size: Filter Pack Used: Surface Seal: Annular Seal: Monument Type: 8 1/4 inches inches Notes/Comments: Soil boring only, no well installed. Page: 7 of 7

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