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l <br /> . j <br />! plegia Trucking, Inc. <br /> September 28, 1990 <br /> Page-6- <br /> alluvial fan and floodplain environments and were derived <br /> primarily from the erosion of the Sierra Nevada mountain range <br /> to the east. <br /> i <br /> u< 4.2 Site Geology <br />+ i <br /> 1 <br /> Interbedded layers of sand, silty 'sand, and silty clay r <br /> were exposed in the excavation (Figure 4) . The upper 2 feet <br /> of the subsurface is old pavement and road-base. Below this <br /> 1 _ and extending down to approximately 10 feet is thinly <br /> interbedded coarse sand, and poorly-sorted, .fine-to medium- <br /> grained silty-sand. Between the 10-foot1 and 20-foot depths isi <br />� silty-sand. 9his .layer was stained with product prior to <br /> removal . Below this, and extending down to ::5 feet, is well- <br /> sorted medium-grained white sand. From' 28 feet to at least 31 <br /> i <br /> feet (total excavation depth) is firm, silty- <br /> clay. This lowest silty-clay zone was ;well cemented and may <br /> impede downward migration of hydrocarbons. <br /> f <br /> f 5.0 LABORATORY ANALYSIS <br /> The eight soil samples collected from the excavation were <br /> 1 analyzed for benzene, toluene, ethyl benzene, and xylene <br /> i <br /> - (BTEX) by EPA Method 8020, for total extractable petroleum <br /> hydrocarbons, as diesel (TEPH) by Method 3550/Mod.8015 and for <br /> total volatile petroleum hydrocarbons,', as gasoline (TVPH) by <br /> Method 5030/Mod.3015. <br /> CONDOR <br /> i <br /> t <br />