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Central Valley Regional Water Quality Control Board <br />17 December 2020 <br />Heorot Power Holdings <br />Attn: Barbara Guiltinan <br />575 Broadway <br />New York, New York 10012 <br />“DRAFT” ADDITIONAL SITE ASSESSMENT REPORT REVIEW, FORMER SAN <br />JOAQUIN COGENERATION, 17200 MURPHY PARKWAY, LATHROP, SAN <br />JOAQUIN COUNTY <br />Staff of the Central Valley Regional Water Quality Control Board (Central Valley Water <br />Board) have reviewed the 21 October 2020 Additional Site Assessment Report (Report) for <br />the Former San Joaquin Cogeneration Facility (SJCF) located at 17200 Murphy Parkway in <br />Lathrop, San Joaquin County (Site), prepared on your behalf by AdvancedGeo, Inc. (AGI). <br />The objective of the investigation was to define the limits of soil impacted with <br />polychlorinated biphenyls (PCBs) and total petroleum hydrocarbons (TPH) and to further <br />delineate the limits of the North Waste Cell and South Waste Cell. <br />Background <br />Pilkington North America (PNA) operated a plant at 17100 Murphy Parkway, which is <br />situated immediately east of the site. The former PNA facility contained unpermitted <br />landfill cells that resulted in discharge of wastes, including dioxin/furan compounds, <br />PCBs and petroleum hydrocarbons to soil. Two primary waste cells reported as the <br />North Waste Cell and South Waste Cell were reportedly assessed and remediated on <br />the Pilkington property up to what was thought to be the boundary of the cogeneration <br />plant. At the time of remediation, the property boundary was estimated and not <br />established by licensed surveyors. <br />In March and April 2019, AGI conducted a soil and groundwater investigation, <br />documented in the 15 May 2019 Site Assessment Report. A total of 43 direct-push soil <br />borings (B1 through B43) were advanced across the Site to define and evaluate the <br />extent and characteristics of the North and South landfill cells that were thought to <br />extend onto Site property, the former facility footprint, as well as underlying groundwater <br />characteristics. The objective of the borings was to locate and identify unpermitted <br />landfilled waste buried in the area as well as to determine if historical property uses <br />adversely affected subsurface conditions at the Site. Monitoring wells MW-1 through <br />MW-4 were installed to evaluate groundwater flow conditions. A total of 58 soil and <br />waste samples and 10 groundwater samples were collected and analyzed during the <br />site assessment. A summary of the results are as follows: