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• • Work Plan for Septic DraInfieId Investigation March 7,2013 8700 Thornton Rd. Project No.1091 Stockton,California Page 1 INTRODUCTION This work plan presents our approach, methods, procedures and a schedule to conduct an investigation of a septic tank drainfield at an active auto repair facility located at 8700 Thornton Road in San Stockton, California ("the Site"). The Site location is shown on Figure 1. The lead regulatory agency for this case is the Central Valley Regional Water Quality Control Board (RWQCB). The Site is owned by Richard Sola. The environmental consulting and construction firm for the project is Cook Environmental Services, Inc. (CES). The RWQCB caseworker is Ricardo Cervantes. Background The Site is presently an automobile repair facility and has operated as an auto repair facility since about 1990. Prior to that, the Site was a gas station and auto repair facility. The UST fuel tanks were removed prior to 1990. Soil contamination was not detected in soil samples collected beneath these USTs. The City of Stockton Public Works Department recently extended a sewer service to this portion of Stockton. The sewer main runs parallel to Thornton Road. A routine inspection of the septic tank was conducted by the Public Works Department's contractor after the site was connected to the City sewer line. Approximately 1,200-gallons of oily liquid was discovered in a 1,500- gallon concrete septic tank located at the back of the property. The San Joaquin County Department of Environmental Health (SJCEH) was contacted and a Notice to Abate Order was issued. The order directed the Owner to remove the liquid contents, the septic tank and the attached piping. The SJCEH transferred regulatory oversight of the case to the Central Valley Regional Water Quality Control Board (RWQCB). Mr. Roberto Cervantes is the RWQCB caseworker for this site. The Owner contracted Fremouw Environmental Services (FES) to remove the oily waste and clean the septic tank in early October. The oily waste was hauled off as hazardous waste by FES on October 26, 2012. The Owner contacted Cook Environmental Services, Inc. (CES) to assist in complying with the order. CES and the RWQCB agreed on a phased approach to the project. The first phase consisted of removing the septic tank and investigating for the presence of contaminants in the septic tank excavation. This phase was completed in December 2012. The subject of this work plan is the second phase, which is to investigate the potential presence of contaminants in the drainfield. CES prepared a Work Plan for Septic Tank Removal and a Site Specific Health and Safety Plan dated November 19, 2012 to remove the septic tank. The RWQCB approved the work plan in a letter to the owner dated December 4, 2012. The septic tank was removed in compliance with the work plan on December 6 and 7, 2012. Hydrocarbon contaminated soil was detected in the