ARCHIVED REPORTS XR0009907 - Laserfiche WebLink

Home Browse Search

i �A Working To Restore Nature January 11, 1993 ARCO Service Station No 2130, Stockton, California GROUND-WATER MONITORING Field work was conducted by RESNA and Emcon Associates (Emcon) of Sacramento, I 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 A summary of our field procedures is attached Subjective Analyses and Water-Level Measurements On July 8,�1992, a technician from Emcon measured depths to water and performed subjective analyses of ground water A technician from RESNA was onsite on August 10, 1992, to take water-level measurements and collect ground-water samples for subjective analyses from wells MW-1 through MW-3, and on September 15, 1992, the technician measured water levels and collected water samples for subjective analyses from monitoring wells MW-1 through MW-3 and the newly installed monitoring wells MW-4 and MW-5 (discussed under Work In Progress section) No floating product, product sheen, or obvious, product odor was noted in samples from the wells during the site visits (Table 1) The wellhead elevations of the monitoring wells at the site were previously surveyed by Tom • Morrow of West Sacramento, California, a licensed land surveyor (California Land Surveyors No 5161) The surveyed elevations and the depth-to-ground-water measurements, summarized in Table 1, were used to evaluate the potentiometric surface beneath the site The ground-water flow dire c on on July 8, 1992, was to the southeast with a hydraulic gradient of 0 002 (Plate 3) 1 Ground-Water Sampling and Analyses On July 8, 1992, Emcon collected ground-water samples from monitoring wells MW-1 through MW-3 for laboratory analyses A RESNA technician visited the site on August 28, 1992, to collect water samples from the two new wells (MW-4 and MW-5) Ground-water samples from wells MW-1 through MW-3 were analyzed for total petroleum hydrocarbons as gasoline (TPHg) and benzene, toluene, ethylbenzene, and total xylene isomers (BTEX)using Environmental Protection Agency(EPA) Methods 5030 and 8020 and standard methods prescribed by the State of California These samples were analyzed at Columbia Analytical Services, Inc in San Jose, California (Hazardous Waste Testing Laboratory Certificate No 1426) Samples from wells MW-1 through MW-3 were also submitted to Sequoia Analytical in Sacramento, California, for analysis of fecal coliform bacteria. These samples were also to be analyzed for total coliform bacteria if fecal coliform bacteria were not detected The samples collected on August 28, 1992, from wells 1003-6 300003-6 } 2