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Department of Toxic Substances Control <br /> Maureen F. Gorsen, Director <br /> Linda S.Adams 8800 Cal Center Drive Arnold Schwarzenegger <br /> Secretary for Sacramento, California 95826 Governor <br /> Environmental Protection <br /> April 17, 2007 <br /> Mr. Mark Clardy <br /> Central Valley Regional Water Quality Control Board <br /> 11020 Sun Center Drive #200 <br /> Rancho Cordova, California 95670 <br /> COMMENTS ON REMEDIAL ACTION REPORT, MOUNTAIN HOUSE <br /> NEIGHBORHOOD C & D, MOUNTAIN HOUSE AREA, TRACY, CALIFORNIA <br /> (SITE CODE 104465) <br /> Dear Mr. Clardy: <br /> At the request of the Central Valley Regional Water Quality Control Board, Department <br /> of Toxics Substances Control (DTSC) reviewed the Remedial Action Report (RAR) for <br /> the Mountain House Neighborhood C & D (RAR, SAIC, March 2007). The RAR address <br /> the remediation of a 5,200 foot alignment of two former Shell Oil Central Valley Crude <br /> Pipelines that transect Neighborhood C & D. DTSC's primary focus in this review was in <br /> regard to the 1 ,000-foot (Areas 3, 4, 5) section of pipeline that transect the <br /> southwestern portion of the future Mountain House High School (MHHS). <br /> Excavation depths along the pipeline alignment in Areas 3, 4 and 5 ranged from <br /> 10 to 24 feet below ground surface (bgs). Confirmation samples were collected on the <br /> floor and sidewalls of the excavation and analyzed for total petroleum hydrocarbons <br /> (TPH) as diesel and crude oil; and benzene, toluene, ethylbenzene and xylenes. Soil <br /> gas samples were collected northeast of Areas 3, 4 and 5 at depths of 5, 10 and 15 feet <br /> bgs. The sampling results indicate minor TPH (a maximum of 360 mg/kg) and benzene <br /> impacts to soil at the proposed MHHS site. Based on a review of the data provided in <br /> the RAR, DTSC does not believe the existing levels of TPH or benzene would <br /> contribute a significant health risk to students or staff at the proposed MHHS site. <br /> Enclosed are comments regarding the RAR for Areas 3, 4, and 5. <br /> c' <br /> 1.. <br /> rj <br /> N Cb4r <br /> 0 <br /> ® Printed on Recycled Paper <br />