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California P -;ional Water Quality Contr-1 Board a Central Valley Region <br /> Katherine Hart,Chair <br /> Arnold <br /> Linda S.Adams <br /> 11020 Sun Center Drive#200,Rancho Cordova,California 95670-6114 Schwarzenegger <br /> Secretary for Phone(916)464-3291 •FAX(916)464-4645 <br /> Governor <br /> Environmental http://www.waterboards.ca.gov/centralvalley <br /> Protection <br /> RECIEVED <br /> 9 February 2010FEB 1 U NAB <br /> &�z� <br /> qll <br /> Mr. John MacLeod ENV�RONMSER�CE,T <br /> Chevron Environmental Management Company P�RITI <br /> 6001 Bollinger Canyon Road, Room K2276 <br /> San Ramon, CA 94583 <br /> ADDENDUM TO SITE CLOSURE REPORT, CHEVRON CORRAL HOLLOW AND GRANT <br /> LINE ROADS, TRACY, SAN JOAQUIN COUNTY <br /> California Regional Water Quality Control Board, Central Valley Region (Central Valley Water <br /> Board) staff reviewed the 12 November 2009 Addendum to Site Closure Report(Report) <br /> submitted by ARCADIS on behalf of Chevron Environmental Management.Company <br /> (Chevron) for the site at Corral Hollow and Grant Line Roads in Tracy (Site). <br /> The Report was submitted in response to our 17 September 2009 letter which requested <br /> additional information prior to reviewing the Site for closure. Chevron included the requested <br /> table of well construction details, summary of sensitive receptors in the area, and cross <br /> sections showing Site lithology. In addition, the Report includes a work plan for the installation <br /> of four soil borings around monitoring wells MW-6 and MW-7. <br /> Our comments are included below: <br /> 1. Central Valley Water Board staff concurs with Chevron's proposal to drill four soil <br /> borings near MW-6 and MW-7 and collect soil samples at four and eight feet below <br /> ground surface (bgs). Depth to water at the Site is about nine feet bgs, and Chevron <br /> needs to collect a grab groundwater sample from each boring. Soil and groundwater <br /> samples need to be analyzed for total petroleum hydrocarbons as gasoline (TPHg), <br /> TPH as diesel, and benzene, toluene, ethylbenzene, and xylenes (collectively BTEX). <br /> By 30 April 2010, Chevron needs to drill the soil borings, collect and analyze the soil <br /> and groundwater samples, and submit a report of findings. <br /> 2. The Report states that Chevron does not believe the soil concentrations detected in <br /> soil boring SB-8 warrant additional assessment based on the location of the <br /> contamination beneath Grant Line Road. In 1995, soil samples collected at SB-8 <br /> contained TPI-Ig and BTEX were 1,500 milligrams per kilogram (mg/kg), 5.6 mg/kg, <br /> 75 mg/kg, 57 mg/kg, and 390 mg/kg, respectively. These concentrations exceed the <br /> San Francisco Bay Region Environmental Screening Levels (ESLs) for gross <br /> contamination of soils. None of the other soil borings contained concentrations above <br /> the ESI-s. Prior to Site closure, Chevron needs to collect soil data in this location to <br /> determine whether these concentrations still exceed the ESI-s. Chevron may consider <br /> Site closure with a deed restriction if it does not want to collect these soil samples. By <br /> California Environmental Protection Agency <br /> �a Recycled Paper <br />