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Rain Water Car Wash - 2- 23 May 2017 420 Yosemite Ave, Manteca San Joaquin County By 31 July 2017, please submit a Work Plan which includes a proposal for borings to define the downgradient extent of MTBE in groundwater. In order to avoid future delays, as part of the Work Plan preparation process, please investigate possible access issues for the recommended locations. Please note that once the downgradient extent of MTBE is defined, monitoring wells may be necessary for confirmation, and to establish trends and evaluate stability. 2. During the September 2016 groundwater sampling event (most recent), AGE reported chlorinated solvents trichloroethylene (TCE) and tetrachloroethylene (PCE) in serval Site wells. AGE reported TCE above reporting limits in 11 of the 50 Site wells, and PCE above reporting limits in 27 wells. Additionally, with the exception of P11 at 60 feet bgs, AGE reported TCE and/or PCE in all grab groundwater samples collected from borings P11, P12, P14, and P15. In the Groundwater Monitoring Report— Third Quarter 2016, dated 11 November 2016, AGE did not include TCE and PCE data in analytical Table 2. While the detected PCE and TCE do not appear to come from the Site, Central Valley Water Board staff request that future Groundwater Monitoring Reports (GMRs)include all historical PCE and TCE analytical data in Table 2. The next GMR is for 3° quarter 2017, and should be submitted by 30 October 2017. 3. Central Valley Water Board staff request that you collect shallow soil samples to compare Site conditions with the Direct Contact and Outdoor Air Exposure criteria presented in the State Water Resources Control Board's Low Threat Underground Storage Tank Case Closure Policy(LTCP). According to Central Valley Water Board files, you have not collected soil from depths shallower than 10 feet bgs. In the Work Plan due 31 July 2017, please include a proposal to collect a sufficient number of samples to adequately assess hydrocarbon concentrations in soil between 0 and 5 and between 5 and 10 feet bgs. In summary Central Valley Water Board staff request the following: • By 31 July 2017, please submit a Work Plan which includes: o A proposal for borings to define the downgradient extent of MTBE in groundwater. o A proposal to collect sufficient samples to adequately assess hydrocarbon concentrations in shallow soil between 0 and 5 and between 5 and 10 feet bgs. • By 30 October 2017, please submit the 3d Quarter 2017 GMR, and include all historical PCE and TCE analytical data in the tables.