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Central Valley Regional Water Quality Control Board <br />12 August 2019 <br />Charles Skobrak <br />9947 E. Highway 26 <br />Stockton, CA 95215 <br />AUG 1 6 2b19 <br />ENVIRONMENTAL HEALTH <br />PERMIT/SERVICES <br />GAVIN NEwsol,t <br />GOVERNOR <br />JARED BLUMENFELD <br />SECRETANV FOR <br />ENVIRONMENTAL PROTECTION <br />LARRY'S AUTO, 308 N. GRANT STREET, STOCKTON, SAN JOAQUIN COUNTY, <br />CASE# 390170 <br />On 8 August 2019, Central Valley Regional Water Quality Control Board (Central Valley <br />Water Board) staff had a conference call with Mr. Daniel Villanueva and Mr. Brian Millman <br />of Advanced GeoEnviron mental Inc. (AGE) to discuss the path forward for the Larry's Auto <br />unauthorized petroleum release case at 308 N. Grant Street in Stockton (Site). <br />During that conference call, Central Valley Water Board and AGE staff concurred on the <br />following for the Site: <br />1. The extent of petroleum impact to groundwater is not defined in either the area of <br />former underground storage tanks (USTs) A and D (Tank Area 1) or USTs B and C <br />(Tank Area 2). The only off -Site downgradient assessment performed was 2005 <br />borings CPT -5 and CPT -9, which are located too far south and west, respectively, <br />to properly defined the plume. <br />2. Assessment of hydrocarbon impact to shallow groundwater is needed in Tank Area <br />2. The monitoring wells in the area, MW -4 and MW -8, are all screened at least 20 <br />feet below first encountered groundwater. Additionally, the grab groundwater <br />sample in 2001 boring CPT -2 was collected approximately 40 feet below the <br />groundwater surface at the time. <br />Remedial wells VW -6 thru VW -9 are located in Tank Area 2 and are screened <br />between 10 to 35 feet bgs. As such, it may be possible to sample these wells to <br />assess Tank Area 2 hydrocarbon at the groundwater interface. <br />3. Due to the presence of benzene in excess of 1,000 micrograms per liter (ug/L) in <br />groundwater samples collected from MW -5, assessment of soil gas in the vicinity of <br />MW -5 and the surrounding structures is necessary to evaluate vapor intrusion risk. <br />4. Historical remediation performance report <br />s indicate that soil vapor extraction and air <br />sparge (SVE/AS) has removed a total of approximately 15,810 pounds of <br />KARL E. LONGLEY SCD, P.E., CHAIR � PATRICK PULUPA, ESO., EXECUTIVE OFFICER <br />11020 Sun Center Drlve #200, Rancho Cordova, CA 95670 � Tvww.waterboards.ca.gov/centralvalley <br />6� RECYCLED PAPER <br />