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Forward Landfill Hydraulic Testing Technical Memo July 03, 2019 • achieved with conveyance and/or pump upgrades. Conveyance line upgrades conducted in June 2019 have increased pumping capacity to 95 gpm. Hydraulic step testing conducted on extraction well EW-2 was pumped up to an extraction rate of 83 gpm which did not stress the well or aquifer capacities and indicated pumping rates of 90-110 gpm could be achieved with conveyance and/or pump upgrades. Conveyance line upgrades conducted in June 2019 have increased pumping capacity to 100 gpm. Hydraulic step testing conducted on extraction well EW-4 was pumped up to an extraction rate of 65 gpm, with the swell or aquifer indicating a decrease in capacity after 54 gpm. The optimal pumping rate for this well is currently in the region of 45-55 gpm. However, review of drillers logs indicate that there is potential for higher rates and increased capacity might be obtained through rehabilitation of the well. Previous constant rate testing performed on EW-3R(Arcadis, 20193), provided hydraulic conductivity for the aquifer materials and indicates that the extraction zone is indicative of a semi-confined or leaky aquifer. These aquifer parameters were used, along with estimated saturated thickness of the hydraulic unit(s),to assess the capture radius for each of the extraction wells. The calculated capture widths with well pumping rates optimized are presented in Table 6. Groundwater capture have been significantly enhanced with the increased pumping rates, but full capture is not indicated in portions of the POC. Chemical assessment of groundwater collected from the extraction wells(Table 7) indicated that the western portion of the POC extraction wells have detectable concentrations of VOCs while the eastern extraction wells VOC concentrations were non-detect. The non-detect concentrations in the extraction • wells along the eastern portion of the POC are likely in part attributed to a hydraulic barrier created by groundwater mounding from the GWTS infiltration basin located to the north of the eastern portion of the POC. It is interpreted that in this portion of the POC groundwater flows back towards the landfill. Also, groundwater leaving the Site appears to be hydraulically directed towards the western portion of the POC, before flowing northwards. Increased extraction and capture capacity in the western portion of the POC is indicated to be required for full capture of impacted groundwater. RECOMMENDATIONS Due to apparent control of groundwater(by extraction and mounding) in the eastern portion of the Forward landfill POC, combined with non-detect concentrations of COCs, it is recommended that the existing extraction well(EW-1 and EW-4)pumping rates are optimized and extraction well EW-4 is rehabilitated to potentially increase the extraction capacity. The western portion of the POC is indicated by hydraulic testing results to not have full groundwater capture, and this portion of the POC also indicates detectable concentrations of COCs. Therefore, an additional extraction well is recommended to enhance capture along the western portion of the POC, placed between extraction wells EW-3R and EW-2.With the addition of the proposed well it is anticipated that groundwater capture of the western portion of the POC will be complete. 3 Arcadis 2019,Well Installation and Hydraulic Testing Summary Report for Forward Landfill, San Joaquin • County, California, dated April 15. arcadis com FL Specific Capacity Test Memo 07032019.docx Page: 6/7