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9 , 0 130 Robin Hill Road 5 17 100 <br /> n Ltio [fll iii! U�[�11 Santa Barbara 0 93117 <br /> A Division of URS Corporation Tel $05 964 6010 <br /> Fax 805 964 0259 <br /> February 4, 2000 <br /> Offices Worldwide <br /> Ms Margaret Lagorio, REHS <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> 304 E Weber Avenue, Third Floor <br /> Stockton, California 95202 <br /> Re Caltrans District 10 Shop 10 Maintenance Station, 1603 South B Street <br /> Project No. 4104010004 <br /> Dear Ms Lagorlo <br /> On behalf of Caltrans District 10, URS Greiner Woodward Clyde (URSGWC) is pleased to submit to <br /> San Joaquin County Public Health Services (SJCPHS) groundwater analytical results and figures <br /> depicting groundwater data at the Shop 10 Maintenance Station The site is located at 1603 B Street, <br /> Stockton, California (Figure 1-1) URSGWC collected discrete vertical groundwater samples from three <br /> wells at the Shop 10 site on April 7, 1999 A report describing the sampling procedures, analytical <br /> results, historical groundwater concentration and elevation trends, local well survey, hydraulic <br /> conductivity estimates, and the estimated mass of petroleum hydrocarbons in soil and groundwater is in <br /> progress The completed report will be submitted to your office within 30 days The results will be Used <br /> to the human health risk assessment and evaluation of remedial alternatives to be conducted fol the <br /> Shop 10 site <br /> BACKGROUND <br /> On February 10, 1999 a meeting was held with the Central Valley Regional Water Quality Control Board <br /> (CVRWQCB) and the SJCPHS At that meeting it was agreed that an additional groundwater <br /> investigation was needed to complete the delineation of petroleum hydrocarbons at Shop 10 before <br /> preparing the Human Health Risk Assessment and Groundwater Impact Analysis Report The additional <br /> site investigation data and analysis that were requested included <br /> • A survey of public and private groundwater wells within 500 feet of Shop 10 <br /> o Vertical delineation of petroleum hydrocarbons in groundwater <br /> • Estimation of hydraulic conductivity <br /> • Estimation of petroleum hydrocarbon mass in soil and groundwater, and <br /> o Estimation of natural attenuation to CVRWQCB Basin Plan concentrations <br /> Task 1 —Survey of Public and Private Groundwater Wells <br /> At the February 10, 1999 meeting, the CVRWQCB requested a survey of public and private groundwater <br /> wells within 500 feet of Shop 10 URSGWC has reviewed public well records maintained by the <br /> California Water Service and by a private well driller who has installed wells in the vicinity of the site <br /> S 1PROJ141040100044SHOP101SJCPHSLTR SHOP10 DOC 24 2000 <br />