ARCHIVED REPORTS_XR0012733 - Laserfiche WebLink

Home Browse Search

I { i 0- Therefore, a discussion of the leaching potential analysis is included within this report. The LUFT manual Table 2.1 was utilized to estimate the concentra-tions of BT:{&E and TPH that can be safely left in place without threatening water quality based on leaching potential. This Table provides a leaching potential analysis based on Ecosystem Modeling Results and the best professional judgement of experienced California Regional Water Quality Control Board Staff. A part of the analysis requires data on depth ro groundwater, WESTON utilized both a client supplied well installation report for an on-site well located as shown on Figure 1 and the San Joaquin county Flood Control and Nater Conservation District, Lines of Equal 2noth to Water in Wells, Fall 1988 map to determine the depth to first groundwater at the site. The depth was found- to be greater-than 1001 . This depth to first groundwater, coupled with the lack- of :G� �bZurface- fractures, an averageannual" precipitation of appraxiniately 14 . inches, no presence o.f man"made vertical conduits arid no uniquei s' ze features prov_'de a cumulative score from 'Table :2-1 of 49' points. For this sco-s, the LUFT manual recommends 3 maximum allowable TPH level for gasoline of 1000 rrg/Kg and maximum BTX&E levels of 1/50/50/50 mg/Kg respectively. Both the Luft manual Table 2-1 and the well installation report are presented in Appendix C. Based on these considerations, there .does not appear to be any need t for additional site investigation or remediation y the site. However, .the San Joaquin County does not utilizeEthis site specific information and has determined that no TPH concentra- tions, no matter how isolated, may remain in'place in excess g/K9. Therefore, WESTON believes a ..of 100 mminor soil excavation and:., resampling should remove the soils in excess of the County's recommended limits. - 4.3 Soil Stockpiles Sample #1 through n7 were taken from the stockpiled soils removed from Pit A. Sample V'8 was taken from the stockpiled soils removed from Pit B. A review of the data presented in Table 1 indicates that TPH, BTX&E, EDB and total lead were detected within these stockpiles at very low con cantrations. The concentrations detected are well below the levels which would designate the stockpile as hazardous waste. 5.0 .Conclusions and Recommendations -- --- ---------- T e-anaiytica�-results for samples taken from Pit A indicate that no concentrations of hydrocarbon related compounds remain in the excavation. Therefore, it is recommended that this area be closed. t. The analytical results for samples from Pit B indicate limited amounts of petroleum hydrocarbon .compounds are present in the - 7 T I