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• California Regional Nater Quality Control Board <br /> ` Central Valley Region o . <br /> k <br /> Robert Schneider,Chair <br /> Alan C.Lloyd,Ph.D. Arnold <br /> Secretaryfor Fresno Branch Office i 2' 27 Schwarxenegger <br /> Environmental 1685 E Street,Fresno,California 93706 Governor <br /> Protection (559)445-5116•Fax(559)445-5910 S tiN c o la jr T Y <br /> http://www.waterboards.ca.gov/centralvalley ENV 1 n 0 t'&1 E 4 T A L <br /> HEl',LTl1 DEYARTtiEMT <br /> 27 October 2005 <br /> M. Scott Mansholt <br /> Chevron Environmental Management Company <br /> 6001 Bollinger Canyon Road, Rin K2066 <br /> San Ramon, California 94583-2324 <br /> SOIL AND GROUNDWATER INVESTIGATION REVIEW AND ADDITIONAL <br /> CHARACTERIZATION WORKPLAN—MOUNTAIN HOUSE SITE#3,MOUNTAIN HOUSE, SAN <br /> JOA QUIN COUNTY <br /> We have reviewed the Soil and Groundwater Investigation Report and Additional Characterization <br /> Workplan, Mountain House Site #3 Property, Mountain House, dated 5 October 2005 for the Chevron <br /> Old Valley Pipeline (OVP) project site, northwest of Tracy, CA. Site#3 is located at the southeast <br /> intersection of Byron Road and Mountain House Parkway, northwest of the City of Tracy, in western <br /> San Joaquin County. Currently, the site and surrounding area is agricultural land under development to <br /> residential and/or commercial properties. <br /> Previously, a site investigation completed in November 2001 (sixteen soil borings) indicated the initial <br /> discovery of petroleum hydrocarbons in soil and groundwater was confirmed attributable to historical <br /> OVP leaks. Elevated concentrations of petroleum hydrocarbons in four of the sixteen borings were <br /> reported in soil (at the maximum depth investigated, 46.5 feet) and the groundwater samples collected; <br /> free phase petroleum on groundwater was reported in three borings. Depth to groundwater ranged <br /> between 5.5 feet and 13.5. The soil and groundwater impacts were not delineated and additional <br /> characterization was required; a workplan was submitted and approved by Regional Board staff. <br /> The purpose of the current investigation was to characterize subsurface soils and groundwater in the <br /> vicinity of the former OVP where in November 2001, impacted soil and groundwater was identified. <br /> The October 2005 investigation report describes the advancement of nine soil borings and collection of <br /> samples for laboratory analysis to provide an evaluation of the extent of total petroleum hydrocarbon <br /> (TPH)-impacts identified in 2001. <br /> Borings MH3-1 through MH3-9 were advanced in the general vicinity of previous borings GP-96, 97, <br /> 117, and 173 to characterize/delineate the previously identified impacts. The borings were advanced to a <br /> target depth of 35 feet with the exception of hydropunch boring MH3-1B, which was advanced to 58 feet <br /> to delineate the vertical extent of TPH-affected soil and groundwater. Groundwater samples were <br /> obtained from six of the borings, including one from the hydropunch boring at 50 feet to evaluate the <br /> vertical extent of impacted groundwater. <br /> California Environmental Protection Agency <br /> 00 Recycled Paper <br />