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June 16, 1997 Page 4 • Soil samples from the borings were analyzed for TPH-g, BTEX compounds, MtBE, and TPH-d Soil analytical results detected petroleum concentrations in three of the eight borings In borings B-2 and MW-4, TPH-d was detected at concentrations of 13 and 10 ppm at 11 and 16 feet bgs, respectively MtBE was detected at a concentration of 0 18 ppm at 1 I feet bgs in Boring B-1 No other detectable concentrations of hydrocarbons were reported in the borings The results of groundwater sampling at the site in February 1996 indicated nondetectable concentrations of hydrocarbons in groundwater Soil and groundwater analytical data are presented as Tables i and 2, respectively Quarterly groundwater monitoring of the wells at the site was performed from February 1996 through February 1997 by PACIFIC and Blaine Tech Services, Inc (Blaine Tech) With the exception of 0 64 ppb toluene and 2 8 ppb MtBE reported in Well MW-1, and 0 64 ppb benzene, 1 5 ppb toluene, 0 73 ppb xylene, and 13 ppb MtBE reported in Well MW-2 in May 1996, nondetectable concentrations of hydrocarbons have been reported in the groundwater since the wells were installed in February 1996 EXTENT OF HYDROCARBON PRESENCE IN SOIL AND GROUNDWATER Based on the results of previous investigations performed at the site, the results of UST, • product line, and dispenser replacement activities, and soil over-excavation, it appears that the majority of residual petroleum hydrocarbon impacted soil was removed during UST replacement activities in September 1995 On February 12, 1996, groundwater samples from the monitoring wells (MW-I through MW-4) were analyzed for TPH-g, BTEX, MtBE, and TPH-d Groundwater analytical results indicated nondetectable concentrations of petroleum hydrocarbons in all samples collected Subsequent quarterly monitoring of the wells indicated nondetectable to very low concentrations of hydrocarbons in groundwater The most recent two quarters of monitoring data indicate nondetectable concentrations of hydrocarbons in all the wells at the site Historical groundwater analytical data is shown on the attached Cumulative Table of Well Data and Analytical Results (Blaine Tech, Attachment G) BENEFICIAL USES OF GROUNDWATER PACIFIC identified a total of 39 wells located within a 112-mile radius of the site No known shallow aquifer drinking water wells are located within a 112-male radius of the site, and drinking water in Ripon is provided by the City of Ripon Mr Matt Machado, Civil Engineer with the City of Ripon Public Works Department, stated in a telephone conversation on May 1, 1997, that the City of Ripon derives one hundred percent of it's municipal drinking water supply from deep groundwater wells The closest municipal well (0) is located approximately 0 4-miles upgradient from the site Well construction regulations require that all drinking water wells be properly sealed to prevent entry of 9201026AICLOSERPT