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California Regional Water Quality Control Board <br /> Central Valley Region <br /> (Catherine Hart,Chair <br /> 1685 E Street, Fresno,Calilbrnia 93706 <br /> MBt(lieir Rodriguez o59)445-51 16• FAX(559)445-5910 Edmund G.Brown Jr. <br /> Secrelatr for Imp,Ilwwu.waterboards.ca.govlcentralvalley Governor <br /> Pi7vrrownenlal Protection <br /> TO: Douglas K. Patteson gl <br /> Supervising Engineer <br /> DATE: 19 January 2012 <br /> FROM: C. Dean Hubbard <br /> Engineering Geologist <br /> P. G. No. 6357 <br /> Shelton R. Gray <br /> Senior Engineering Geologist <br /> SUBJECT: CONSIDERATION OF REQUEST FOR NO FURTHER ACTION REQUIRED <br /> DETERMINATION, MOUNTAIN HOUSE DEVELOPMENT SITE #6, WEST <br /> BYRON ROAD, MOUNTAIN HOUSE, SAN JOAQUIN COUNTY <br /> Rationale: Historical Old Valley Pipeline (OVP) and Tidewater Associated Oil Company <br /> (TAOC) crude oil pipelines crossed the approximate center of the Mountain House Site #6 <br /> project (Site). OVP and TAOC are predecessors of Chevron Environmental Management <br /> Company (Chevron). Crude oil affected soil and groundwater has been delineated in two <br /> areas with approximate dimensions of 175 feet by 250 feet and 320 feet by 720 feet. The <br /> vertical extent of affected soil was defined by non-detect (ND) analytical results for samples <br /> collected from boring depths of about 26 to 39 feet below ground surface (bgs). The area of <br /> affected groundwater is slightly larger than the smaller of the two outlined areas of affected <br /> soil. Impacted groundwater within the second affected soil area has two irregular shapes of <br /> about 200 by 250 feet and 300 by 350 feet, and overlap with two defined areas within the <br /> outline of affected soil. <br /> Fuel fingerprint analysis and evaluation indicated the petroleum hydrocarbons are consistent <br /> with weathered San Joaquin Valley crude oil. Two refined petroleum products pipelines are <br /> reported to be within the easement, but the alignment/locations are unknown. Affected soil <br /> and groundwater areas occur primarily within and beneath the West Byron Road easement, <br /> elongated parallel to and within/beneath the approximate alignment of the historical crude oil <br /> pipelines and the active pipelines. Future Site use is not anticipated to change. <br /> A human health screening evaluation (HHSE) completed in January 2011 , considered an <br /> exposure by a construction worker and a residential risk scenario which is a conservative <br /> estimate of risk associated with potential exposure to crude oil at the Site. The approach is <br /> consistent with a land use scenario described in the California Department of Toxic <br /> Substances Control (DTSC) Preliminary Endangerment Assessment (PEA) Guidance Manual. <br /> California Environmental Protection Agency <br /> w� Reeved Paper <br />