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Mr Harlin Knoll August 25, 1998 Page 4 RESULTS No gasoline hydrocarbons were detected in the soil samples collected from borings DB-2 and DB-3 at depths of approximately 35 feet Gasohne hydrocarbons were detected in each of the remaining soil samples selected for laboratory analysis TPHg concentrations ranged from nondetectable (bottom of each boring)to 4,500 ppm (45 5 feet bgs in DB-1), and benzene concentrations ranged from 0 008 to 14 ppm Petroleum hydrocarbon contamination in all three borings attenuated with depth, with the highest concentrations between 45 and 55 feet The samples collected from the bottom of each boring (98 5 feet bgs in DB-la and 70 5 feet bgs in 1313-211313-3) contained no detectable TPHg, but minor concentrations of BTEX were detected No gasoline oxygenate additives were detected in the samples selected for analysis of VOCs However, minor concentrations of various gasoline constituents were detected Analytical results are summarized in Table 1 Laboratory reports and chain of custody information are contained in Attachment D The highest hydrocarbon concentrations in the soil were detected between 40 and 50 feet bgs, which corresponds to the zone of historic groundwater fluctuation The lateral extent of groundwater contamination has been essentially defined, except to the northeast Groundwater grab samples collected from borings DB-1 through DB-3 contained TPHg concentrations ranging from 69,000 to 180,000 parts per billion (ppb), and benzene concentrations . ranging from 2,000 to 27,000 ppb Analytical results are summarized in Table 1 Laboratory reports and chain of custody information are contained in Attachment D SUWUqARY OF FINDINGS SINGS O Field observations and laboratory results suggest that residual hydrocarbons remain in soil and groundwater beneath the northeastern portion of the site • The lughest hydrocarbon concentrations in soil were detected in boring DB-1, located adjacent to the fonner USTs, at 45 5 feet bgs This depth corresponds to the historic zone of groundwater fluctuation(40-50 feet bgs) • Other than the 35 5 foot sample from DB-1, all soil samples with detectable hydrocarbons were collected below first encountered groundwater The potentiometnc surface beneath the site currently exists at approximately 34 9 feet, as measured in well MW5 ® Petroleum hydrocarbons in soil attenuated with depth G Gasoline oxygenate additives were not detected in soil samples collected from DB-1 at depths of 66 and 98 5 feet a Groundwater was encountered in the borings a depths ranging from 39 5 to 43 feet kwMes h=Vcpoftslinvrpcaoo