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Limited Site Assessment Work Plan Stockton, S West Lane ��, Hydrogeological Stockton,San Joaquin County, CA `"`{ '///)Associates Based on a review of historical documents presented in the 2016 Phase I Environmental Site Assessment, the subject property appears to have been developed as an engine repair shop (trucks and/or tractors) since at least 1937. Records indicate subject parcel 117-090-07 was further developed with a single-family dwelling until 2006, when the dwelling and associated residential improvements were removed. Directory listings indicate the property has been occupied by R & L Diesel Service since at least 1960, prior to that Siefert R R Trucking occupied the property during the mid1950s. In April 1998, R&L Diesel abandoned a waste oil underground storage tank (UST) which was closed in place by filling with concrete. No soil samples were collected for analysis adjacent to or beneath the tank during UST abandonment activities. On February 26, 2007, two direct-push soil borings were advanced and soil samples collected at sixteen (16) foot below ground surface (bgs). Concentrations in the soil sample from the tank top were below the laboratory's detection levels. However, Total Petroleum Hydrocarbons, as Diesel (TPH-D) and volatile organic compounds (VOCs) were detected in the soil sample collected from beneath the tank. The results of this investigation are presented in a June 8, 2008 Report of Investigation. In March 2008, Environeering, Inc. (EI) advanced four direct-push Geoprobe soil borings to further define the lateral and vertical extent of petroleum hydrocarbon contamination. Borings B1 and B2 were vertical borings drilled four feet north of the former UST and five feet west of the fill pipe for the former UST, respectively (Figure 2). Boring B1 was advanced to 44 feet bgs and boring B2 was advanced to 48 feet bgs. Borings B3 and B4 were slant borings drilled 11 feet northwest of the fill pipe and 11 feet southwest of the fill pipe, respectively. Boring B3 was drilled 24° from vertical to a total length of 32 feet (approximately 29 feet bgs) and B4 was drilled 18" from vertical to a total length of 24 feet (approximately 19 feet bgs). On April 20, 2009, Taber Consultants advanced vertical boring B-5 approximately 7.5 ft. from the center of the abandoned UST. Six (6) soil samples were collected from boring B-5. Each of the soil samples was analyzed for TPH-D and TPH-G by EPA Method 8015M and for volatile organic compounds, including BTEX and PCE, by EPA Method 8260B. The laboratory reported all soil samples results were below laboratory's minimum detection limits (MDL). Additionally, one groundwater sample was collected from the boring and analyzed for TPH-D and TPH-G by EPA Method 8015M and for volatile organic compounds, including BTEX and PCE, by EPA Method 82608. The laboratory reported that the groundwater sample results were below the laboratory's detection limits for all analytes except for PCE at a concentration of 4.1 micrograms per liter (ug/1). This concentration is below the California Primary Maximum Contaminant Level (PMCL) of 5.0 ug/I. A No Further Action Request was submitted by Taber Consultants on September 9, 2009, with a supplemental report addressing vapor intrusion issues issued on September 15, 2009, and No Further Action was granted by San Joaquin County in a letter dated October 23, 2009. The site was closed by 2