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' i Clayton Gl.U' 11-7" impacted soil [2 feet to 5 5 feet below ground surface (bgs)] at boreholes GP-1, GP-2, and GP-9 The analytical results for these samples indicated diesel range hydrocarbons ' ranging up to 39 mg/kg, with no detectable gasoline range hydrocarbons, ethylbenzene, or xylenes These results indicate that the biodegradation was effective for this material and that limited concentrations of hydrocarbons In the diesel range remained ' The site investigation also detected moderate to elevated diesel range hydrocarbons in two samples, each collected insitu from within the boundaries of the former excavation ' The 10-foot bgs sample from GP-1 indicated 2,900 mg/kg diesel-range hydrocarbons and the 10-foot bgs sample from GP-9 indicated 140 mg/kg diesel range hydrocarbons Each ' of these samples was collected from the pea gravel present in the bottom of the former excavation No BTEX compounds were detected in any of the samples, and gasoline range hydrocarbons were detected only in the 10-foot bgs pea gravel sample from GP-9, ' at a concentration of 3 3 mg/kg Diesel and gasoline range hydrocarbons were detected within the bounds of the former ' tank excavation with lateral migration of up to 20 feet Diesel range hydrocarbons in the groundwater beneath this area were found to range from 5 3 mg/1 to 330 mg/l and gasoline range hydrocarbons from 0 15 mg/l to 0 87 mg/1 Concentrations of diesel fell ' off rapidly to below 10 mg/l in the surrounding area Gasoline was not detected outside the area described above The limited migration of these hydrocarbons is likely due to the fine-grained soil with relatively low permeability BTEX was not detected in groundwater samples collected from outside the limits of the former tank excavation Benzene In the groundwater beneath the former UST showed a ' marked decrease from those reported at the time of the tank removal Benzene was reported at 80 µg/1 ' Methyl Tertiary Butyl Ether(MTBE) decreased from 3,200 µg/1 reported at the time of the tank removal to a maximum of 36 µg/1 during the October 2000 sampling The highest MTBE concentrations were present within the tank excavation and immediate ' vicinity, with no evidence of significant migration Based on information from the Limited Soil and Groundwater Sampling Report as ' summarized above, the impacts related to the former USTs at the site are attenuating naturally The PHD/EHD reviewed the 2001 report and subsequent transmittals from The Learner Company Based on this information, the agency requested that a limited ' groundwater investigation be conducted which is the subject of the current investigation This request included the installation of three groundwater monitoring wells on the periphery of the zone of impact to determine if significant migration of fuel-related ' compounds is occurring These wells are required to be monitored quarterly for a period of one year Following this monitoring period, the site status is to be reevaluated 2 ' S\Proj\P02263\Q1 Rpt doc