ARCHIVED REPORTS_XR0008405 - Laserfiche WebLink

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C A M B R I A Mr Jeffrey Wong February 15, 2006 2001 Receptor Survey Cambria conducted a receptor survey and identified 12 water producing wells within a 2,000-foot radius of the subject site using California Department of Water Resources records Six of the wells were installed for domestic use, one was for irrigation use, two were for industrial use, one was for municipal use, and two wells were of unknown use The closest well is a municipal well located approximately 1,100 feet northeast (cross-gradient) of the Shell-branded station The approximate well locations are plotted on Figure i No additional wells were identified by Cambria's 500-foot door-to-door survey Two surface water bodies were also identified within the study area Unnamed ponds are located at the San Joaquin Storm Water Facility, which is located approximately 250 feet north of the site, and a diverting canal is approximately 1,900 feet southwest of the site The surface water bodies are also shown on Figure 1 Complete survey results are included in Cambna's February 13, 2002 Fourth Quarter 2001 Groundwater Monitoring/Site Investigation Report and Receptor Survey 2005 Tank Removal and Over-Excavation During March 18, 2005, Shell removed two 15,000- gallon gasoline USTs, four dispensers, and associated product piping No petroleum constituents were detected in soil from the UST excavation Following removal of the equipment, Cambria conducted over-excavation and soil sampling in some of the dispenser and piping areas on April 1 and 4, 2005 Up to 11,000 ppm TPHg, 10 ppm benzene, and 0 11 ppm MTBE were detected in soil during these activities Cambria presented these results in the June 20, 2005 Underground Storage Tank Removal and Over-Excavation Report Groundwater Monitoring Program There are currently seven groundwater monitoring wells (MW-1 through MW-7) on site that are sampled quarterly Groundwater monitoring wells MW-5 through MW-7 were installed between December 12 and December 16, 2005 during this investigation Historically, groundwater flow beneath the site is predominantly northerly During the third quarter 2005 sampling event, TPHg was detected in well MW-1 at 81 parts per billion (ppb) The laboratory noted that the hydrocarbons reported as TPHg did not match the laboratory's gasoline standard MTBE was detected in wells MW-1 and MW-2 at 130 and 0 55 ppb, respectively Based on the quarterly groundwater monitoring and dispenser sampling results, SJCEHD requested additional investigation Cambria submitted the requested work plan and work plan addendum on September 14, 2004 and July 5, 2005, respectively, and presents the results of this work below 3