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California Regional Water Quality ontrol Board . . <br /> Central Valley Region w �. <br /> Robert Schneider,Chair �.. <br /> Alan C.Lloyd,M.D. Arnold <br /> Secretary for Fresno Branch Office Schwarzenegger <br /> Environmental I685 E Street,Fresno,California 93706 Governor <br /> Protection (559)445-5116•Fax(559)445-5910 <br /> http:/Iwww.waterboards.ca.gov/centmlvalley <br /> 13 April 2005 R* ' <br /> v�' <br /> APR 14 2x05 <br /> M. Scott MansholtCS <br /> Chevron Environmental Management Company <br /> Property Management <br /> 6001 Bollinger Canyon Road <br /> P.O. Box 6012 <br /> San Ramon, CA 94583-0712 <br /> REVIEW OF SOIL SAMPLING AND ,ANALYSIS WORKPLAN, MOUNTAIN HOUSE SITE #6, <br /> MOUNTAIN HOUSE, SAN JOAQUIN COUNTY <br /> We have reviewed the Workplan for Soil and Groundwater Investigation, Mountain House <br /> Development, Mountain House Site #6, submitted by Science Applications International Corporation <br /> (SAIC) on behalf of ChevronTexaco. The workplan proposes collecting additional soil and groundwater <br /> samples in the vicinity of crude oil pollution previously identified in borings completed at the site in <br /> 2001 by Condor Earth Technologies, Inc. (Condor). <br /> According to our files, the initial discovery of petroleum hydrocarbons in soil was confirmed attributable <br /> to leaks from the Old Valley Pipeline (OVP) that had existed on Mountain House Site#6. Mountain <br /> House Site #6 encompasses an approximate length of 1,000 feet and is located approximately 700 feet <br /> northwest of the intersection of Byron and Wicklund Roads, northwest of the City of Tracy, in western <br /> San Joaquin County. <br /> During the Condor investigation, elevated concentrations of petroleum hydrocarbons were reported in <br /> soil borings GP-152, GP-156 through GP-158, GP-160, and GP-161 at depths ranging from 4.5 to <br /> 20 feet. Petroleum hydrocarbons as crude oil (TPHc) in soil at depths of 6.5 to 12 feet contained TPHc <br /> at concentrations ranging from 880 to 29,000 mg/kg. <br /> Depth to groundwater beneath the site ranged from 7 to 17 feet; several groundwater samples were <br /> collected and submitted for analysis. TPH as diesel (TPHd)were detected at concentrations ranging <br /> between 2,200 micrograms per liter(µg/L) and 260,000 pg/L; TPH as gasoline (TPHg) concentrations <br /> ranging from 8,500 to 9,900 µg/L were detected. Highest TPH concentrations in groundwater were <br /> present in GP-161. <br /> The workplan proposes the installation of 30 primary borings and 12 contingency borings to collect soil <br /> and groundwater samples for laboratory analysis to delineate the lateral and vertical extent of petroleum <br /> hydrocarbon constituents. Maximum depths of the proposed borings will be 30 to 35 feet. Additionally, <br /> California Environmental Protection Agency <br /> Qp Recycled Paper <br />