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M Y-11-95'THU 16:07 CONDOR EARTH TECH IFAX NO. 2096689248 P. 02 �• pi sa1,n-ten Ftdropmach Leiter ARaEh 11.1"1 On May 6, 1994, a total of 3 soil samples were Coll, ted following over-excavation of soil along the east sidewall of the former locations of TKA, TK4 and T15. One soul sample was collected from the floor of the over-excavation at a depth of approximately 15.5 feet bgs Two soil samples were collected from the east sidewall approximately 15 feet bgs Md approximately 12 feel apart_ Laboratory analyses 0� the soil sauaple collected from the floor of the over-excavation detected 6.3 /kZ toluene and 10 µglkg xylene- Total petroleum hydrocazbons quantified as kerosene, diesel and mator oil were not deteded at or above the i ruparted laboratory detection limits in the soil sample colle&m fmm the floor of the over-excavati6n. I Laboratory analyses of the soil samples collected from the eat sidewall indicated no evidence of hydrocarbon contamination at or above the reported laboratory detection limits. No petroleum staining, odors or OVA readings were noted du ring the over excavation. Based on the results of field observations and laboratory analyses, Condor concluded that the lateral extent of soil Wntaminwou at the site had been evaluated. the complete descriptions of the results of the'UST removal and a over excavation arse in Underrgrorrrrd Storage Tank Removal - Soil Sampling Results, Condor Earth Technologies, Inc., October 14, 1993, and Over- ayarion Soil Sampling Re4ulh, Condor Earth Technologi , Inc., Pune 21, 1994, respectively. DIS&SSION The draft version of the 'mater Quality Site Assessm t for Soil and Groundwater'(WQSA document) prepared by the Calit'ornia Regional Water Quality Control Board, Central Valley Region (CRWQCI:3,CVR), sales that a contaminate detected in soil does nut threaten water quality if the soil, leachate concerxtration for that sample is less than or equal to the back pound ground w ter concentm ion, regardless of whether background is greater than or less than the numerical water quality limit. The May, 1993, Recommended- Uniting Water Quality Goals for Components of Petroleum Based Fuels prepared by the CRWQt:B indicates that, for the hydrocarbon coinaitaents detected at the Di Sal - Lathrop site, the following water quality goals are applicable: benaene= 1.0 �tgfl, toluene = 42.0 }igfl, ethyl benzene= 29.0 pgll and Xylene,= 17 AgA hydrocarbon mixtures of kerosene and diesel= 10 }tjVl for lifetime health advisory. To evaluate if hydrocarbon constituents detected in fie soil may lead, into groundwater, a soil samplo collected from above the water table, may be analyzed using Title 22 CCR Waste Extraction Test(WET). By performing a WET on a soil.sample collected from above the water table; a quantitative assessment of the leachable hydrocarbon constituents that present a risk to Sm water quality can be assessed. The detoctable CONDOR