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Eo«unu 6.Bnowx Jn. <br /> /'b� ovenxox <br /> EIVED � MPTiHEW <br /> WaterR°OOflIe11Ei <br /> Boards REC <br /> Central Valley Regional Water Quality Control Board NOV 1 % 2014 <br /> EWIpONMENTALHEALT14LTH <br /> FERMITISERVICES <br /> Mr. Mark Buller 7 November 2014 <br /> 1137 South Stockton Street <br /> Stockton, CA 95206 <br /> SOIL ASSESSMENT WORK PLAN, IDEALEASE, 1137 SOUTH STOCKTON STREET, <br /> STOCKTON, SAN JOAQUIN COUNTY <br /> California Regional Water Quality Control Board, Central Valley Region (Central Valley Water <br /> Board) staff reviewed the 20 October 2014 Soil Assessment Work Plan (Work Plan) submitted <br /> by Advanced Geo Environmental, Inc. on behalf of Idealease for the property at 1137 South <br /> Stockton Street in Stockton (Site). The Site consists of an office building; truck wash facility; <br /> fuel dispenser area; and one 12,000-gallon diesel aboveground storage tank (AGT). The Site is <br /> paved with asphalt and concrete and a canopy covers the truck wash and dispenser areas. <br /> The Work Plan proposes advancing three soil borings to about 10 feet below ground surface <br /> (bgs) and collecting soil samples to define the southern extent of soil contamination at the Site. <br /> Idealease proposes drilling one soil boring in the location of previous high concentration <br /> EXC.B-S2 to confirm the presence of TPHd in this location. Two additional borings are <br /> proposed to be drilled southeast and southwest of the confirmation boring to define the lateral <br /> extent of contamination that exceeds direct contact limits for unrestricted use. The Work Plan <br /> also states that if the southern soil borings contain contamination, it will drill one additional <br /> boring 15 to 20 feet south of the initial boring locations. <br /> Our comments are: <br /> 1. Central Valley Water Board staff concurs with the installation of three (and possibly four) <br /> soil borings to a total depth of 10 feet bgs to define the southern lateral extent of the soil <br /> contamination that exceeds direct contact limits for unrestricted use at the Site. <br /> Idealease needs to collect soil samples at the depths of previous high concentrations <br /> (4 to 6 feet bgs) and one from the bottom of the boring. Soil samples should be <br /> analyzed for TPI-Id, benzene, ethylbenzene, toluene, and xylenes. By <br /> 31 December 2014, Idealease needs to drill the soil borings, collect and analyze the soil <br /> samples, and submit a report of findings. <br /> 2. Central Valley Water Board staff also noted in our 17 September 2014 letter that soil <br /> samples collected from the eastern sidewall of the excavation near the dispenser islands <br /> (Area A) contained concentrations above the California Regional Water Quality Control <br /> Board — Bay Area Region Environmental Screening Levels (ESLs) for gross <br /> contamination. Idealease is not proposing further soil borings to define this area. <br /> Figure 3 of the Work Plan includes an isoconcentration line around the area showing <br /> TPHd detections in soil. It is unclear if Idealease is indicating that the eastern sidewall <br /> detection in Area A excavation extends to the Area B excavation. Idealease should <br /> KARL E. LONOLEV SOD, P.E.,CHAIR I PAMELA G. CREEDON P.E., BCEE,EXECUTIVE Orr1OER <br /> 11020 Sun Center Drive X200,Rancho Cordova,CA 86670 I www.wWerboards.ca.9ov/c.ntralvall.y <br /> ,J ne.YG......v. <br />