SITE INFORMATION AND CORRESPONDENCE

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Harding Lawson Associates March 16, 1992 John Bruener Company Mr.Peter M.Meier 92006430.02 Page 2 PHS/EHD Comment#2-PHSIEHD is concerned that a 3.5 foot deep excavation was conducted and Sample#91060606 and Sample #91060607 were taken from only 1.5 feet and 2.0 feet below the surface at the southerly walls. The sampling did not provide analytical verification of the full extent of the excavation activity. HLA Response-It is HLA's opinion that the soil samples provided analytical verification of the extent of excavation activity because soil samples#91060606 and#91969697 were collected from the southern excavation wall to evaluate the horizontal extent of petroleum hydrocarbons in soil. To evaluate the vertical extent of petroleum-impacted soil,a floor sample was also collected from a depth of 3.5 feet at a location approximately 7 feet north of sample#91060607. PHS/EHD Comment#3 -In your support for site closure, we would recommend a sampling event take place that provides for adequate verification sampling of the horizontal and lateral aspects of the overexcavation. HLA Response-It is HLA's opinion that the soil samples collected provide adequate characterization of soil remaining in-situ following excavation activities. Soil removed from the excavation was screened for the presence of petroleum hydrocarbons using an organic vapor analyzer (OVA). When it appeared that soil containing petroleum hydrocarbons had been removed,soil samples were collected from the walls and floor of the excavation. Soil samples were collected in areas where soil exhibited elevated OVA readings,staining,or the soil color and OVA measurements were representative of the entire wall. Soil samples were collected using a grid matrix pattern of approximately 10 feet. Two samples were collected from the 220 square foot excavation floor and five samples were collected from the walls of the excavation. (One of the floor samples was collected in the vicinity of the former island.) One wall sample was collected from the 100 square feet of excavation wall north of the former dispenser island and approximately one wall sample was collected for every 50 square feet of excavation wall south of the former island. (It should be noted that the former product conveyance lines and vapor recovery lines ran south from the dispenser islands to the former tanks,thus the higher sampling density in the southern part of the excavation.) PHS/EHD Comment#4-PHS/EHD recommends that a "Leaching Potential Analysis"be completed (L.U.F.T. Manual, Table 2-1)for any contaminant detected by lab analysis that is proposed to be left in place. HLA Response-HLA has completed a leaching potential analysis for the only chemical constituent detected in soil samples collected from the excavation (see attached table): (12 milligrams per kilogram total petroleum hydrocarbons[TPH]as motor oil). In preparing the leaching potential analysis,HLA used Table 2-1 from the L.U.F.T. manual. This table ranks the leaching potential of TPH as gasoline and diesel,and not TPH as motor oil. Because motor oil is less soluble than diesel or gasoline, the leaching potential analysis represents a worse case scenario. On the basis of the leaching potential analysis, the concentration of TPH as motor oil detected in soil at the site is well below the maximum allowable level for both TPH as gasoline and diesel.