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-ION Californi*egional Water Quality CAM Board <br /> QW; Central Valley Region <br /> Karl E. Longley, ScD,PE,Chair <br /> Linda S.Adams Arnold <br /> Secretary for Fresno Branch office Schwarzenegger <br /> Environmental 1685 E Street,Fresno,California 93706 <br /> Protection (559)445-5116 -Fax(55 9)445-5910 Governor <br /> http://www.waterboards.ca.gov/centralvalley <br /> 7 May 2007 <br /> MAY 0 9 2007 <br /> EI~IVIRONI LENT HEATH <br /> PERMIT/SERVICES <br /> M. Scott Mansholt <br /> Chevron Environmental Management Company <br /> 6001 .Bollinger Canyon Road <br /> Room K2066 <br /> San Ramon, CA 94583-2324 <br /> REVIEW OF SOIL INVESTIGATION WORKPLAN, MOUNTAIN HOUSE SITE#5, <br /> MOUNTAIN HOUSE, SAN JOAQUIN COUNTY <br /> Regional Water Board staff has reviewed the referenced workplan, dated 23 April 2007 <br /> prepared by Science Applications International Corporation (SAIC) on behalf of Chevron. The <br /> project site is located along Byron Road, the railroad tracks, the former Old Valley Pipeline <br /> (OVP) and Tidewater Associated Oil Company (TAOC) rights-of-way, approximately 1,900- <br /> feet southeast of S. Kelso Road and about five miles northwest of Tracy. The site and <br /> adjacent properties' land use is for agricultural purposes; nearby properties are under <br /> residential and/or commercial development. Byron Road is being expanded to accommodate <br /> increased traffic in the area. <br /> Earlier investigations completed by Condor Earth and SAIC between 2001 and 2006 identified <br /> areas of affected soil and groundwater primarily beneath Byron Road, the railroad tracks, and <br /> the former OVP and TAOC pipelines alignments. Soil was defined in lateral extent to <br /> approximately 150-feet in width, less than 32-feet deep in an area generally centered on <br /> boring MH5-1. However, the lateral extent of affected groundwater downgradient of MH5-7 <br /> (total petroleum hydrocarbons as diesel [TPHd] @ 350 fag/1) has not been adequately defined. <br /> Depth to groundwater is between 8 and 18-feet with a north-northeast gradient. <br /> The workplan proposes three additional borings downgradient of MH5-7 to obtain soil and <br /> groundwater samples for analysis. Soil samples from the upper ten-feet will be collected and <br /> analyzed for consideration and completion of a human health risk screening evaluation. The <br /> maximum boring depth proposed is approximately 40-feet. <br /> California Environmental Protection Agency <br /> eb*Recycled Paper <br />