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C A M B R I A Based on the analytical results from these soil samples, Cambria returned to the site on February 4, 1999 and conducted over-excavation to several locations Soil samples were collected subsequent to over-excavation Soil to the UST area was excavated to non-detect concentrations, except for one sample along the northern tank wall, which contained 0 395 parts per million (ppm) MTBE by EPA Method 8260A at 13 feet below grade (fbg) The area was further excavated, later in February 1999, when Stockton Service Station Equipment Company, Inc (SSSEC) of Stockton, California installed new, larger USTs, as discussed below Soil beneath the northern two dispenser islands and associated piping contained residual benzene and MTBE at maximum concentrations of 0 962 and 60 4 ppm These concentrations were at 12 5 fbg beneath the northwesternmost dispenser Soil beneath the western dispenser island was excavated to non-detect concentrations These activities are described in Cambria's June H, 1999 Underground Storage Tank Removal Report During February 1999, SSSEC installed a new gasoline UST, a new diesel UST, and five dispensers for the current station owner/operator in roughly the same locations as the former USTs and dispensers Based on the February 1999 soil over-excavation results, Cambria drilled four soil borings near the northern dispensers and associated piping during February 2000 One of these borings was converted into a monitoring well (MW-5) Total petroleum hydrocarbons as gasoline (TPHg) and benzene were not detected in soil or groundwater during this investigation MTBE was detected by EPA Method 8260A in groundwater from well MW-5 at a concentration of 10 3 parts per billion (ppb) during the initial sampling event Complete details of this investigation may be found in Cambria's September 8, 2000 Site Investigation/First Quarter 2000 Groundwater Monitoring Report Based on the mitral groundwater monitoring results, SJCPHS/EHD and the RWQCB requested additional assessment The results of these investigation activities are presented below INVESTIGATION RESULTS Personnel Present Cambria geologists Scott Lewis and Geno Mammini directed the field activities working under the supervision of California Registered Geologist Joe Neely Permit Well permit No 0024476 was obtained from SJCPHS/EHD (Appendix A) 1346 2