ARCHIVED REPORTS_XR0002833 - Laserfiche WebLink

Home Browse Search

' GEGMATRIX . 2.1 OCCURRENCE AND DISTRIBUTION OF DETECTED TPH FOR SOIL SAMPLES Reported analytical results for soil samples(Table 2)and a review of bonng log data indicate that the area of soil potentially impacted by petroleum related constituents is present over an area of approximately 140 by 110 feet(Figure 3)and at depths from approximately 10 to 30 feet bgs Although no soil bonngs were advanced in the railroad corridor to the west of the site,the lateral ' extent of soil potentially affected by a release of petroleum constituents from the former UST is estimated to extend approximately the same distance from the former UST as was observed in soil bonngs advanced to the west of the former UST TPHd has been detected in soil at concentrations up to 14,000 mg/kg(in a sample from the bonng for monitonng well MW-2, collected beneath the former UST) TPHg has been detected in site soil samples at concentrations up to 870 mg/kg,also in a sample collected from the boring for monitonng ' well MW-2 Neither benzene nor methyl tertiary butyl ether(MTBE)has been detected in soil samples collected at the site Toluene, ethylbenzene,and xylenes have only been detected in the 2 soil samples collected from the boring for monitonng well MW-2 at concentrations up to 13, 0 11, and 4 2 mg/kg,respectively Idealized geologic cross-sections depicting the potential extent of affected soil,based both on reported visual observations from boring logs as well as analytical results 1 i from samples, are presented as Figures 4 and 5 ' Based on the estimated lateral and vertical extent of TPH affected soil and a review of the analytical results, it is estimated that the mass of residual TPH at the site is approximately 40,000 to 50,000 pounds,which equates to approximately 5,200 to 6,500 gallons of residual TPH fuel remaining in site soil It is estimated that approximately 75 percent of the mass is located in an area approximately 60- feet in diameter around the location of the former tank excavation and at depths of 10 to 30 feet bgs ' 2. MP2 OCCURRENCE AND DISTRIBUTION OF DETECTED TPH FOR WATER SALES Groundwater samples collected from monitonng wells installed within the affected soil area(wells MW-2,MW-3,and MW-4)have been reported by analytical laboratones to be impacted by petroleum-fuel related analytes including TPHd,TPHg,and one or more of the aromatic hydrocarbon compounds benzene,toluene,ethylbenzene,and xylenes MTBE has not been reported as detected in groundwater samples collected from the site TPHd and TPHg have been detected in groundwater samples collected from wells MW-2, MW-3, ' and MW-4 at concentrations that exceed water quality objectives(WQOs)established by the Regional Water Quality Control Board,Central Valley Region(RWQCB) The WQOs for TPHd and I\Doc_Safe\9000s\9963\CAPICAP txt doe 3