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4.0 SUMMARY AND CONCLUSIONS The purpose of ICF KE's recent soil and groundwater investigation at the site was to assess current chemical concentrations in soil, and to evaluate the groundwater quality in the ' vicinity of the Tank #4 remediation excavation The results of our soil investigation indicates the presence of TPH-E and toluene-affected soils in the northwest corner of the remediation ' excavation and under the existing ice plant building (northeast corner of the remediation excavation) The residual petroleum compounds in soil appear to reside in a vertical layer ' from apprommately 10 to 25 feet in depth. Mammum concentrations of (170 mg/kg) diesel, (840 mg/kg) kerosene, (72 mg/kg) oil, (41 pg/kg) toluene, and (11 pg/kg) xylenes were ' detected dunng our investigation Given analytical concentrations of historical and present soil samples collected in the ' vicinity of former Tank #4 remediation excavation, the estimated volume and contaminant concentrations remnant in soils is considered minor. Additional soil investigations are not ' deemed necessary or feasible given the low residual concentrations and physical constraints of the adjacent and on-site property usage. The historical remediation activities in the vicinity of former Tanks #3 and #4 appear to have been adequate to protect the quality of underlying groundwater The source of potential contamination (Tanks #1 through #4) have been removed Petroleum-affected soils have been removers to the extent feasible given existing building, adjoining property use, and equipment constraints The removed soil has been bio-remediated off-site Foisting soil type (clay and silt) limits the vertical and horizontal movement of petroleum hydrocarbons remnant in site soils. The building and asphalted stock yard (with the exception of graveled Union ' Pacific right of way adjoining and to west) limit water infiltration in the excavation areas, further limiting the vertical movement of petroleum hydrocarbons in residual affected soils Based on these considerations, additional soil investigations do not appear warranted. ' Our groundwater investigation measured depth to groundwater at approximately 60 feet bgs in the vicinity of the Tank #4 remedial excavation area Diesel-range compounds were detected in MW-3 (0 06 mg/L) which is just above the reporting limit of 0 05 mg/L. The first reported analyses of the groundwater sample collected from MW-5 in October 1994 detected diesel-range compounds (0.1 mg/L) and benzene (5 pg/L), but a re-analysis of the dWti«v« rPE 13 I