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BP #172 (Thrifty) - 3 - 9 March 2017 7647 Pacific Avenue Stockton, San Joaquin County Table 2 below details the criteria for each LTCP Groundwater Specific scenario, and associated Site data. TABLE 2 — LTCP Groundwater Specific Criteria and Associated Site Data Scenari Plume Distance to Closest Maximum Maximum Free Plume Length Well and Surface Benzene MTBE Product Stable to ° (feet) Water(feet) (ug/L) (ug/L) Allowed Decreasing 1 100 250 Applica Not A Not No Yes 2 250 1,000 3,000 1,000 No Yes 3 250 1,000 Not Not Yes Yes for>/= Applicable Applicable 5 years 4 6. 1,000 1,000 1,000 1,000 No Yes Site Undefined Well: 700 10,000 200 No No Surface Water: 100 Additional delineation of the extent of impact to shallow groundwater is needed downgradient of well MW-14. By 19 May 2017, please submit a Work Plan which includes a proposal for the installation of a shallow zone monitoring well near existing well MW-23. 2. It does not appear that the vertical extent of petroleum hydrocarbon impact to groundwater is defined. The highest TPHg and benzene concentrations in deep groundwater are currently in well MW-22 (screened 55-60 ft bgs), with concentrations listed in Table 1 above. MTBE in this well during December 2016 was below an elevated reporting limit of 50 ug/L, and was 210 ug/L in June 2016. Additionally, well MW-3 (screened 47-75 ft bgs) contained 3,800 ug/L benzene in December 2016. As such, additional petroleum hydrocarbon vertical delineation is needed downgradient of the Site. In the Work Plan due 19 May 2017, please include a proposal for the installation of a monitoring well in the vicinity of existing well MW-23 to provide assessment of groundwater deeper than 75 ft bgs: 3. While SVE has previously removed a significant petroleum hydrocarbon mass from the Site, remaining petroleum hydrocarbons in groundwater and significant mass removal reported during the 2015 pilot test indicate that SVE/AS could effectively remove additional petroleum hydrocarbons from the Site. By 16 June 2017, please submit a Remedial Action Plan for implementation of full-scale SVE/AS remediation. 4. The Site does not meet LTCP Petroleum Vapor Intrusion to Indoor Air (VI) criteria. While depth to groundwater is greater than 30 feet, total petroleum hydrocarbons (TPH) concentrations in the upper 30 feet of soil exceed 100 milligrams per kilo gram (mg/kg).