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SECTIONONE Introductlon <br /> • This Workplan presents an approach for conducting a human health risk assessment and <br /> groundwater impact analysis for the Caltrans Shop 10 Maintenance Station(Shop 10) Shop 10 is <br /> an active maintenance facility located at 1603 South B Street in Stockton, California Soil <br /> contamination was observed during the removal of four underground storage tanks (USTs) The <br /> tanks historically contained diesel and gasoline fuel Total petroleum hydrocarbons (TPH) were <br /> detected in soil and groundwater in 1987 Site investigation activities have been performed under <br /> the direction of San Joaquin County Environmental Health Division (SJCEHD) and the Central <br /> Valley Regional Water Quality Control Board (CVRWQCB) <br /> A meeting with SJCEHD, CVRWQCB, and Caltrans on September 23, 1998 was held to present <br /> jthe draft workplan and solicit comments before the workplan was implemented Comments on <br /> the techrucal approach of the workplan was not receive <br /> Tins risk assessment and groundwater impact analysis Workplan presents an approach for <br /> conducting a human health screening evaluation and an evaluation of the transport and fate of <br /> petroleum hydrocarbons in soul and groundwater The purpose of this workplan is to develop the <br /> procedures and methodology using guidance from CVRWQCB and SJCEHD which will be used <br /> to assess current and potential future risk to human health and the groundwater The objective of <br /> the risk assessment and groundwater impact analysis is to provide an objective estimation of the <br /> potential current and future risk to human health and groundwater posed by the residual <br /> petroleum hydrocarbons in soil and groundwater If the risk levels are unacceptable, the risk <br /> assessment and groundwater impact analysis may be used for evaluating site-specific remedial <br /> action goals and making risk management decisions on acceptable levels of risk In order to meet <br /> these objective the following tasks will be conducted <br /> Task 1 -Data Evaluation <br /> Task 2 -Risk Assessment <br /> Task 3 -Results of the Risk Assessment <br /> The above tasks will be discussed in more details in the following sections <br /> M SATE BACKGROUND <br /> Shop 10 has been operated as a state highway repair and maintenance yard since approximately <br /> the late 1940s Shop 10 is located adjacent and to the south of Caltrans District 10 headquarters <br /> in Stockton, Cahforrua(Figures 1-1 and 1-2) To the west of the site is the Stockton Fairgrounds, <br /> ® cVGIu,RANS040PIMWRKaLNFD=?- r.WW73=NA%SNA 1-1T <br />