ARCHIVED REPORTS XR0001331 - Laserfiche WebLink

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r June 9, 1993 iARCO Service Station 2168, Stockton, California Working To Restore Nature r analyses The technician did not observe floating product or sheen in the two wells during development; however, a sheen was observed on samples from the two wells during sampling Results of subjective analyses are presented in Table 1 r Water purged from the wells was stored onsite in properly labeled 17-E steel drums pending the results of laboratory analyses At ARCO's request, drummed water was removed and disposed of by Balch Petroleum of Pleasanton, California Analylical Methods Soil samples were analyzed for total petroleum hydrocarbons as gasoline (TPHg) using modified Environmental Protection Agency (EPA) Method 8015 and benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) using EPA Method 8020 Laboratory analyses were performed at Sequoia Analytical in Sacramento, California (Hazardous Waste 1 Testing Laboratory No 1624) Results of analyses are summarized in Table 2 Results of Soil Sample Analyses Plate 20 shows the distribution of residual gasoline hydrocarbons in soil at various depths 1 . beneath the site Results of laboratory analyses indicated TPHg was detected in soil samples collected from borings drilled near the dispensers and associated pipelines (B-13 and B-17) at a maximum concentration of 140 parts per million (ppm) The concentrations of TPHg, toluene, ethylbenzene, and total xylene isomers detected in the soil sample from boring B-15, drilled at an angle beneath the waste-oil tank, were less than detection limits, i benzene was detected at 0 013 ppm Based on analytical data collected to date, concentrations of TPHg ranged from below detection limits to 1,700 ppm The highest concentrations of TPHg (750 to 1,700 ppm) were detected at depths of 31 feet (B-14) and 41 feet (B-16) bsg near the northwest and southeast corners of the site TPHg was detected in soil at similar depths (26 to 41 feet bsg) at several other drill locations throughout the site PRESENT GROUND-WATER MONITORING Field work was conducted by RESNA and EMCON Associates (EMCON) of Sacramento, California EMCON was contracted by ARCO, EMCON subsequently forwarded their field notes and the laboratory reports to RESNA Data obtained from EMCON is presented in the Appendix to this report On February 23, 1993, a technician from RESNA measured the depth to water in the five monitoring wells, and on March 10, 1993, a technician from EMCON measured depths to j 0209ccar 31009-7 3