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y <br /> ' •, EDMUND G. BROWN JR. <br /> OPM1- 1���,! GOVERNOR <br /> MATTHEW <br /> .� <br /> C A L I f O R N l• `� SECRETARY ROODRIQUEZ <br /> WaterBards ENVIRONMENTAL PROTECTION <br /> Central Valley Regional Water Quality Control Board <br /> 17 June 201VED <br /> 6 <br /> 32016 <br /> Bonny Carter I�JVVlROP�"�,q�1�ITAJ_HEALTH <br /> Director of Facilities and Planning PROl"� TENTAI_HES <br /> Tracy Unified School District <br /> 1875 W. Lowell Avenue <br /> Tracy, CA 95376 <br /> RE: SITE INVESTIGATION WORK PLAN, DELTA ISLAND SCHOOL, 11022 WEST <br /> HOWARD ROAD, STOCKTON, CALIFORNIA <br /> Dear Ms. Carter: <br /> Central Valley Regional Water Quality Control Board (Central Valley Water Board) staff have <br /> reviewed the Site Investigation Work Plan (Work Plan) dated 20 April 2016 prepared by GHD <br /> Services Inc. for the former Delta Island School property located at 11022 West Howard Road <br /> in Stockton, California (Site). The objective of the Work Plan is to determine the extent of <br /> petroleum hydrocarbons in soil and groundwater in the vicinity of a former transformer pad. <br /> Background <br /> The Site is an approximately 8-acre parcel of land located at 11022 West Howard Road in <br /> Stockton, San Joaquin County, California. The Site was the location of Delta Island School, an <br /> elementary school in the TUSD. The school was constructed between 1971 and 1973 and <br /> demolished in 2009. Prior to school construction the land was used for agricultural crop <br /> production. <br /> Soil samples collected at a depth that ranged from the surface to 7.5 feet (ft) below ground <br /> surface (bgs) near a former transformer pad in June 2015 and February 2016 indicated that the <br /> soil had been impacted by petroleum range hydrocarbons. Total petroleum hydrocarbons as <br /> diesel (TPH-d) were detected as high as 81,000 milligrams per kilogram (mg/kg) in a surface <br /> soil sample collected in June 2015. Total petroleum hydrocarbons as motor oil (TPH-mo) has <br /> been detected in soil samples also as high as 962 mg/kg. A subset of samples analyzed for <br /> total petroleum hydrocarbons as gasoline (TPH-g) and polychlorinated biphenyls did not contain <br /> those chemicals at concentrations above laboratory detection limits. <br /> Proposed Scope of Work <br /> The Work Plan proposes to advance approximately ten soil borings around the former <br /> transformer pad to a depth of 15 ft bgs to delineate the horizontal and vertical extent of <br /> petroleum hydrocarbon impact. Up to three soil samples will be collected from each boring <br /> based on visual observation of staining and field screening using a photo-ionization detector <br /> KARL E. LONOLEY SCD, P.E., CHAIR I PAMELA C. CREEDON P.E., BCEE, EXECUTIVE OFFICER <br /> 11020 Sun Center Drive#200,Rancho Cordova,CA 95670 I www.waterboards.ca.gov/centralvalley <br /> i�RECYCLED PAPER <br />