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SECTIONONE Qatr®duci9®lD <br /> The following Human Health Risk Assessment and Groundwater Impact Analysis for the Caltrans <br /> Shop 10 Maintenance Station (Shop 10) in Stockton, California has been prepared to evaluate <br /> Potential health risks and potential groundwater quality impacts posed by residual petroleum <br /> hydrocarbons in soil and groundwater This assessment is part of Caltrans Contract 43X930 Task <br /> Order Number 4 This risk assessment has been performed using the approach in the October 1998 <br /> Workplan written by Woodward-Clyde International Americas (WCIA) and submitted to the San <br /> Joaquin County Environmental Health Division (SJCEHD) and the Central Valley Regional Water <br /> Quality Control Board (CVRWQCB) for review A meeting with SJCEHD, CVRWQCB, and <br /> Caltrans on September 23, 1998 was held at the SJCEHD office in Stockton to present the draft <br /> workplan and solicit comments before the workplan was implemented Written comments <br /> regarding the technical approach of the workplan were not received from the agencies <br /> Shop 10 is an active maintenance facility located at 1603 South B Street in Stockton, California <br /> Soil contamination was observed during the removal of four underground STs tanks storage (U } <br /> The tanks historically contained diesel and gasoline fuel Total petroleum hydrocarbons (TPH) <br /> were detected in soil and groundwater in 1987 Site investigation activities have been performed <br /> under the direction of SJCEHD and CVRWQCB for the past 12 years <br /> 1.i REGULATORY FRAMEWORK <br /> Several statutory and regulatory provisions provide the State Water Resources Control Board <br /> (SWRCB), Regional Water Quality Control Boards, and local agencies with broad authority to require <br /> responsible parties to cleanup a release from a petroleum UST(e g,Health and Safety Code 25299 37, <br /> Water Code 13304, subdivision a) SJCEHD has been designated as an agency to participate in the <br /> local oversight program for the abatement of and oversight of the abatement of unauthorized releases <br /> of hazardous substances from USTs (Health and Safety Code 25297 1) The SWRCB has <br /> promulgated regulations specifying corrective action requirements for petroleum UST cases(Cal Code <br /> of Regs Title 23 § 2720-2728) The regulations define corrective action as "any activity necessary to <br /> investigate and analyze the effects of an unauthorized release, propose a cost-effective plan to <br /> adequately protect human health, safety, and the environment and to restore or protect current and <br /> potential beneficial uses of water and implement and evaluate the effectiveness of the activity(ies)" <br /> (Cal Code of Regs Title 23 § 2720) Corrective action consists of one or more of the following <br /> phases (1) preliminary site assessment, (2) soil and water investigation, (3) corrective action plan <br /> implementation, and(4)venfication monitoring (Cal Code of Regs Title 23 § 2722, subd(a)) <br /> woodwW&Oyft ® T11997W73ONNAISfocKmN%REPoRrsHOREPYf7 tsNA 1-1 <br />