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April 14, 1995 Page 3 • of approximate) 25 feet Occasional interla ered silt sands u to 50 feet thick were Y Y Y ( P ) found to the total depth explored Existing hydrocarbon concentrations in the soil appear to be limited to the area around the former product islands Soils in the vicinity of the northern product island at location VW-2, within the depth interval of 20 to 30 feet, were found to have TPH-g concentra- tions ranging from 1,400 to 17,300 ppm with benzene concentrations ranging from 0 27 to 28 ppm Within 15 feet of VW-2, at locations MW-2 and KB-2, soil concentrations decreased to below 28 ppm TPH-g and less than 1 ppm benzene between depths of 25 and 30 feet Soils within the 20- to 30-foot depth interval are within the capillary fringe of the highest anticipated groundwater level (approximate depth of 30 feet) Soils within the area of the northern product islands appear to be defined In the area around the southern product island, Boring KB-3 contained 239 ppm TPH-g and 112 ppm benzene Soils within this area were defined to the north by the tank excavation and to the south by Boring KB-4 An additional discussion of soils delinea- tion at the site is presented in Applied's report dated December 12, 1990 GROUNDWATER CONDITIONS Groundwater occurs beneath the site within the fine-grained deposits, currently between • approximate depths of 44 to 48 feet Groundwater flow at the site has consistently been observed (since 1988) to the northeast at an average gradient of 0 002 The maximum groundwater fluctuation was noted in Well MW-1 at 17 5 feet between 1988 and 1993 Because of the fluctuations in groundwater, Wells MW-1 and MW-2 were dry between 1990 and 1992 Well MW-3 continued to be dry through the first quarter 1993 Separate-phase hydrocarbons have never been observed in site wells Historically, the highest hydrocarbon concentrations have been observed in on-site Monitoring Wells MW-2 and MW-6 PACIFIC previously analyzed five sets of groundwater analytical data between 1989 and 1993 The results of the analysis, presented in PACIFIC's Woik Plan dated August 6, 1993, indicate that the configuration of the hydrocarbon plume has remained relatively stable over the 4-year period Based on recent groundwater monitoring data collected by MPDS, Inc during February 1995, hydrocarbons beneath the site remain stable PACIFIC attributes this finding to the combination of the fine-grained sediments underlying the site, the relatively shallow gradient, and the effects of natural attenuation and degradation processes PROPOSED SCOPE OF WORK The site is underlain by fine-grained material and the groundwater gradient has consis- tently been relatively shallow Because of these conditions, the hydrocarbon plume has • remained almost unchanged since 1989 All underground tanks and lines have been 3100403A1WORKPLAN