ARCHIVED REPORTS_XR0003094 - Laserfiche WebLink

Home Browse Search

Working To Restore Nature Due to the high levels of TPHd in the soil sample collected from the north wall of the pit, RESNA collected a second sample from the north wall on March 17, 1994 The second sample was analyzed by Sequoia Analytical for TPHd using EPA method 3550/8015 modified and for leachable TPHd using the Toxicity Characteristic Leaching Procedure (TCLP, EPA 3510/352018015 modified) The sample was labelled EP-HBEW-8. Analytical results confirmed the presence of elevated levels of TPHd (11,000 ppm) in the soil beneath California Street However, only a small percentage of the diesel contamination is considered leachable, as evidenced by the TCLP analytical results for TPHd (1 3 ppm) The TCLP procedure involves a 20 fold sample dilution factor. Multiplying the leachate concentration of 1 3 ppm by this factor indicates that the soil sample contained 26 ppm leachable TPHd of a total 11,000 ppm or approximately 0 24% Soil sample results are summarized in Table 1 Laboratory reports and chain-of-custody documentation are presented in Attachment 3 Former Waste Oil Tank Location No BTEX constituents, TPHg, oil and grease, HVOs or PCBs were reported in the sample collected from the former waste oil tank pit TPHd (2 6 ppm) was detected The reported concentrations of chromium, nickel and zinc (14, 11 and 29 ppm, respectively) are well below TTLC levels established in the California Code of Regulations (CCR), Title 22 Cadmium and lead were not detected • Stockpiled Soil TPHd (460 ppm) was detected in the composite sample from the stockpiled soil Reported concentrations of detected metals (Table 1) are well below their respective TTLC values. CONCLUSIONS Approximately 160 cubic yards of diesel hydrocarbon impacted soils were excavated from the location of the former underground diesel storage tank Significant concentrations of residual diesel hydrocarbons remain in the soil in the northern portion of the pit where excavation was limited due to the presence of California Street Based on observations during excavation, the zone of residual diesel hydrocarbons is an average of approximately four feet in thickness and extends an unknown distance beneath California Street Based on the areal distribution of the impacted soil south of the former tank location, it can be estimated that the zone of impaction extends approximately 10 to 12 feet beneath California Street, with a total estimated volume of approximately 25 to 35 cubic yards Assuming an average concentration of 5000 to 7500 ppm TPHd in the soil over an average thickness of four feet, the estimated volume of diesel which remains in the soil is between 40 and 85 gallons Of this total, it is estimated that only 0 24% (0.1 to 0 2 gallons) would be leached from the soil Calculations are included in Attachment 4 i BXCA V FNL 4