ARCHIVED REPORTS_XR0001984 - Laserfiche WebLink

Home Browse Search

•` _77_��JKWZWJL A& Working to Restore Nature West Sacramento California, a licensed land surveyor (California Land Surveyors 3275) surveyed the wells on November 19, 1993. On November 3, 1993, our geologist collected soil samples (one composite of four samples) from the stockpiled soil for analyses to evaluate disposal options. At ARCO's request, drill cuttings were transported by Dillard Trucking of Byron, California, to BFI Landfill in Livermore, California, for disposal. Laboratory Methods and Results Select soil samples from the borings were analyzed for total purgeable hydrocarbons (equivalent to total petroleum hydrocarbons as gasoline [TPHg]) with benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) distinction using Environmental Protection Agency (EPA) Methods 5030/8015/8020. Samples were analyzed at Sequoia Analytical in Sacramento,California(California Department of Health Services Hazardous Waste Testing Laboratory Certification 1624). Copies of the Chain of Custody Records and laboratory analysis reports are presented in Appendix C. Results of analyses indicated TPHg was detected in soil samples from boring B-20 at concentrations ranging from 6.4 ppm to 49 ppm; TPHg was not detected in the sample from • -� 41.5 feet bsg in boring B-20. Benzene concentrations in samples from boring B-20 ranged from 0.057 ppm to 0.93 ppm. TPHg and BTEX were not detected in samples from boring B-21. Results of analyses are shown in Table 2. GROUNDWATER MONITORING, FOURTH QUARTER 1993 • EMCON of Sacramento, California, was contracted by ARCO to conduct the field work at the site; EMCON subsequently forwarded their field notes and the laboratory reports to RESNA. Field work included measuring depths to water and collecting groundwater samples for subjective and laboratory analyses. RESNA used these data to evaluate the • direction and gradient of groundwater flow beneath the site. On December 16, 1993, a technician from EMCON measured the depth to water and collected groundwater samples from monitoring wells MW-1 through MW-6 for subjective and laboratory analyses. The field methods and procedures used are presented in an attachment to this report. The technician did not observe floating product or product sheen on samples collected from the wells (Table 1). The surveyed elevations of the top of casing and the depth-to-groundwater measurements (summarized in Table 1) were used to evaluate the potentiometric surface beneath the site. On December 16, 1993, the direction of groundwater flow was east with a gradient of 12I3ccar/30004-8 3