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1.0 Introduction <br /> .3 <br /> 1.1 Objective j <br /> The Remedial Action Plan's (RAP'S) objective is to present a remedial alternative to reduce soil <br /> and groundwater contamination at the petroleum hydrocarbon-impacted zones of the site. This <br /> t <br /> report presents the rationale and design criteria for implementing this remedial alternative. <br /> 1.2 Background <br /> The Shop 10 Maintenance Station (site) is located on the west side..lof South B Street in Stockton, <br /> San Joaquin County, California(Figure 1). The California Department of Transportation <br /> (Caltrans) is currently utilizing the site for equipment storage and maintenance. The site plan is <br /> presented on Figure 2. <br /> Since 1978, numerous investigations have been conducted to characterize the soil and <br /> groundwater impacted with petroleum hydrocarbons released from former gasoline and diesel <br /> underground storage tanks. In addition, several feasibility studies�were completed to evaluate <br /> technologies and were reviewed to select the proposed remedial alternative. <br /> 1.3 Previous Site Activities <br /> This section presents an abbreviated chronology of the site characterization work completed for <br /> the site. This information was compiled and submitted to the agencies in the Initial Site <br /> Assessment (Geocon, 2001). l <br /> In 1978, one of six 19,000-liter(5,000-gallon)underground Istorage tanks (USTs) with unknown <br /> contents was reportedly removed from the site due to a detected leak. <br /> In June 1988, a soil gas survey was performed in the vicinity of the former USTs. Total <br /> petroleum hydrogen as gasoline (TPHg) and/or benzene, toluene,ethylbenzene, and total xylenes i <br /> (BTEX) concentrations were detected in the majority of the26soil gas samples collected at <br /> depths ranging from 2 to 10 meter (m) (7 to 33 feet [ft])below ground surface (bgs). <br /> In 1989, three 19,000-liter (5,000-gallon) gasoline USTs, one 19,000-liter (5,000-gallon) diesel <br /> 11 <br /> UST and one 3,800-liter (1,000-gallon) waste oil UST werel removed from the site. These were <br /> additional tanks not previously removed. Maximum total petroleum hydrocarbons as gasoline <br /> and diesel (TPHg and total petroleum hydrocarbons as diesel [TPHd]) concentrations of 3,700 i <br /> : and 1,700 milligrams per kilogram (mg/kg), respectively, were detected in soil samples collected <br /> ; <br /> {: lj <br /> * SacaP.NisacDP2002WRJiPJ8l8 W2M.at.dac 1.1 <br /> (D1020000) <br /> I1 � <br />