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I I Di &41v0 TruCktag - D.B.S. over-Excavation Jobe 21, 1994 Page -5 I surface indicated no evidence of hydrocarbon constituents analyzed for at the laboratory's reported detecta.on limits. The soil sample collected from Stockpile No. 3 contai-ned 11 µg/kg xylene and 40 mg/kg diesel. 5.0 CONCLUSIONS AND RECOMMENDATIONS Laboratory analyses of the over-excavati-on samples indicated 5 .2 µg/kg toluene and 10 µg/kg xylene in the soil sample collected from the floor of the excavation at a depth of 15 .5 I feet. The two soil samples collected from the east sxdewall at 15 feet below ground surface contained no BTEX or TEPH constituents at the laboratory's reported detecti-on limits . No Ipetroleum staining, odors or OVA readings were noted during the over-excavation. The soil sample collected from Stockpile No. 3 Icontained 11 µg/kg xylene and 40 mg/kg diesel . Based upon the field observations and laboratory results, the lateral extent of soil contamination has been evaluated. Di I Salvo Trucking should request authorization from the SJCEHD to backfill the excavation. However, groundwater at the site may be impacted by petroleum hydrocarbons . Condor recommends a phased Iinvestigation for the Di Salvo Trucking facility to evaluate the lateral extent of groundwater contamination. The first phase of ithe investigation should include the collection of one Hydropunch groundwater sample near the east end of the former location of i TK4 . If hydrocarbon constituents are detected in the Hydropunch groundwater sample, three monitor wells should be installed in a i triangular pattern around the east end of TK4 . Proposed Hydropunch and monitor well locations are shown in Figure 2 , Appendix B. i Soil samples should not be collected for laboratory analyses from the Hydropunch boring. Following collection of the Hydropunch groundwater sample, a split spoon should be driven i i �� CONDOR