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Problem Assessment Report <br />for Soil and Groundwater Contamination <br />l Comgan Property (Project No W0541 00) <br />�I <br />6.0 DISCUSSION <br />6.1 Soil Contamination <br />Field PID readings and supporting laboratory analyses of soil samples collected from borings <br />' SB1, SB4, and SB6 indicate moderate levels of hydrocarbon constituents exist in the soil in the <br />vicinity of the former diesel tank Laboratory analyses did not detect contaminants in outlying <br />'borings MW1, MW3, SB2, SB5 and SB7, indicating impacted soils are limited to a relatively <br />small area. The estimated areal extent of soil contamination is exhibited on Figure 13 <br />It is anticipated that contaminants are limited to the upper ten feet of soil due to the relatively <br />' tight soils and shallow groundwater which tend to inhibit vertical migration of hydrocarbon <br />contaminants. It is estimated that approximately 250 to 300 cubic yards of soil may have been <br />' impacted by petroleum hydrocarbons <br />6.2 Groundwater Contamination <br />' Laboratory analyses of water samples collected from site monitoring wells have not exhibited <br />detectable levels of petroleum constituents (with the exception of xylene [0 6 ppb] in MW2) <br />' since the initial sampling in March 28, 1991. This would suggest groundwater underlying the <br />site is not significantly impacted Localized groundwater contamination may exist where the <br />' groundwater interfaces the suspected impacted soils However the relatively low transmissivity <br />of the soil types impede movement of dissolved hydrocarbons. <br />' 7.0 REMEDIAL ALTERNATIVES <br />Soil remediation alternatives include cap/monitoring, excavation of impacted soil, and in-situ soil <br />venting/vacuum extraction. A summary of each alternative is presented below. <br />1 <br />qp PAR -0393 FNL 6 <br />