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<br />Larry's Auto - 3 - 19 April 2017 308 North Grant Street <br />Stockton, San Joaquin County <br />a sufficient number of shallow soil samples in the vicinity of MW-5. Sample analysis <br />should include TPHg, TPH as diesel (TPHd) and full-scan volatile organic compounds <br />(VOCs). Detailed fuel fingerprint analysis may be warranted in the future based on the <br />results of the soil sampling around MW-5. <br />The Site does not meet LTCP Vapor Intrusion criteria as the maximum benzene <br />concentration in groundwater is greater than 1,000 ug/L (25,300 ug/L in MW-5), and the <br />minimum historical depth to water is less than 30 ft bgs (27.32 ft bgs in MW-7 in <br />September 2012). Additionally, total petroleum hydrocarbons (TPH) in the top ten feet of <br />soil are greater than 100 mg/kg (440 ug/L TPHd at 10 ft bgs in MW-8). Central Valley <br />Water Board staff request that you collect soil gas samples once remediation is <br />complete. <br />The Site does not meet LTCP Direct Contact and Outdoor Air Exposure criteria as there <br />is a lack of data from the northwestern portion of the Site (Tank Area 1). While the <br />criteria are met in the southeastern portion of the Site (Tank Area 2), no soil analytical <br />data is available from shallower than 15 feet bgs in the northwestern portion of the Site. <br />In the Work Plan due 26 May 2017, please include a proposal to collect a sufficient <br />number of samples to assess for petroleum hydrocarbons in soil between 0 and 5 and 5 <br />and 10 ft bgs in the northwestern portion of the Site. <br />While the SVE system has removed approximately 15,810 pounds of hydrocarbons, the <br />system was shut down in August 2016 due to low petroleum hydrocarbon removal rates. <br />As such, vapor rebound testing should be completed during the second and third <br />quarters 2017 to confirm that petroleum hydrocarbons have been removed to the extent <br />practicable. <br />By 30 October 2017, please submit a Remediation Report which details the activities <br />and results of rebound testing, and evaluates the continued efficacy of the system. Any <br />discussion of possible expansion or redesign of the remedial system to address impacts <br />in the vicinity of MW-5, as proposed in the 4Q16 Remediation Report, should be <br />deferred until the results of soil sampling and possible fuel fingerprinting are complete for <br />the MW-5 area. <br />6. In order to properly assess the nature of the release, soil samples from the vicinity of the <br />former waste oil tank should be analyzed TPHg, TPHd, total oil and grease (TOG), <br />VOCs, semi-VOCs (SVOCs), polychlorinated biphenyls (PCBs), and Title 22 metals. It <br />does not appear that these analyses have been performed on soil from the vicinity of the <br />former waste oil tank (Tank D) in the northwest corner of the Site. In the Work Plan due <br />26 May 2017, please include a proposal for the collection of shallow soil in the vicinity of <br />the former waste oil tank, with analysis to include the waste oil analytes listed above. <br />In summary, Central Valley Water Board staff request the following: <br />By 26 May 2017, please submit a Work Plan which includes: <br /> <br />o A proposal for soil sampling in the vicinity of MW-5, with analysis to include <br />TPHg, TPHd, and full-scan VOCs.