ARCHIVED REPORTS_XR0009594 - Laserfiche WebLink

Home Browse Search

KEI-P89-1104 .R9 December 17 , 1992 Page 8 8015 (soil) and EPA method 3510/modified 8015 (water) , total oil and grease (TOG) by Standard Methods 5520B&F (water) and 5520E&F (soil) , and for EPA method 8010 constituents . Selected soil samples from EB5 and EB6 were also analyzed for TPH as diesel, TOG, EPA method 8010 constituents, and for TPH as hydraulic fluid by EPA method 3550/modified 8015 . One soil sample from EB7 was also analyzed for TPH as diesel , TOG, and EPA method 8240 constituents . The results of soil analyses are summarized in Tables 1 and 2 , and the results of the water analyses are summarized in Table 3 . Copies of the laboratory analyses and the Chain of Custody documentation are attached to this report. It should be noted that the water samples from the exploratory borings were collected during drilling . The results of the analyses may not be representative of formation water, and should be used for comparative informational purposes only HYDROLOGY AND GEOLOGY During the drilling of exploratory borings EBI through EB4 , ground water was encountered at depths of 58 . 0 to 58 . 5 feet below grade. In the four existing monitoring wells (MW1 through MW4 ) at the site, the measured depth to ground water on June 22 , 1992 , ranged between 56 . 63 and 57 . 43 feet below grade. Based on water level data gathered on June 22 1992 , the ground water flow direction at the site appeared to be to the east-southeast. The subject site is located adjacent to the Sacramento-San Joaquin delta in the Central Valley geomorphic province. The Central Valley is a large, northwestward-trending, asymmetric structural trough that has been filled with as much as six vertical miles of sediment in the San Joaquin Valley. Based on review of regional geologic maps (U. S . Geological Survey Miscellaneous Field Studies Map MF-1401 "Geologic Maps of the Sacramento-San Joaquin Delta , California" by Brian F. Atwater, 1982) , the subject site is underlain by Holocene and/or upper Pleistocene alluvium identified as Alluvium of Calaveras River and Vicinity (Qcr) . The Calaveras River alluvium was deposited by the Calaveras River, Bear Creek, and several lesser streams, and has not been described in detail The results of our subsurface study indicate that the site is underlain by fill materials that are about 0. 5 to 2 . 5 feet thick, except in the vicinity of MW3 at the former fuel tank pit where pea gravel backfill materials were encountered to a depth of approxi- mately 27 feet below grade. The fill is in turn underlain by 46 alluvium to the maximum depth explored (75 feet below grade)