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F JI � I 11 1} C A M B R I A on January 19, 1999 and collected samples from the tank excavation bottom and beneath the former dispensers,product piping,vapor recovery piping,and vent lines on January 22, 1999 Based on the analytical results from these soil samples, Cambna returned to the site on February 4, 1999 and conducted over-excavation in several locations Soil samples were collected subsequent to over- excavation Soil in 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)methyl tertiary butyl ether (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,respectively These concentrations were at 12 5 fbg beneath the northwestern dispenser Soil beneath the western dispenser island was excavated to below detection limits These activities are described in Cambria's June 11, 1999 Underground Storage Tank Removal Report 1999 Tank Replacement During February 1999,SSSEC installed a new gasoline UST,a new diesel UST, and five dispensers for the current station ownerloperator in roughly the same locations as the . former USTs and dispensers 1999 Soil Borings Based on the February 1999 soil over-excavation analytical results, Cambria drilled four soil borings (SB-1 through SB-4) near the northern dispensers and associated piping during February 2000 One of these bonngs (S13-2)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 InvesugationJFirst Quarter 2000 Groundwater Monitoring Report 2000 Well Installation and 2001 Soil Borings During November 2000, Cambria installed wells MW-6 and MW-8 Soil collected from these well borings did not contain detectable concentrations of TPHg,benzene,or MTBE During April 2001,Cambria drilled five soil bonngs (SB-5 through SB-9) in the vicinity of the northern dispensers Soil collected from these borings did not contain TPHg or benzene Bonngs S13-6 through SB-8 contained low concentrations of MTBE (up to 0 26 ppm)at depths ranging from 14 5 to 39 5 fbg Also in Apn12001,Cambna dnlled a bong to 92 fbg (CPT-2) and collected a groundwater sample at that depth No TPHg, benzene, toluene, ethylbenzene, xylenes (BTEX), fuel oxygenates, 1,2-dibromoethane, or 1,2-dichloroethane were 1346 2 r