ARCHIVED REPORTS XR0009910 - Laserfiche WebLink

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i • February 14, 1992 �� . ARCO Service Station No 2130, Stockton, California Preliminary Subsurface Investigation In June 1991, RESNA Industries (RESNA, formerly Applied GeoSystems) observed Woodward Drilling of Rio Vista, California, drill one soil boring near the fillport ends of the underground storage tanks to evaluate soil in the vicinity of the tanks for possible residual hydrocarbons Hydrocarbons were detected during the field work, therefore,further drilling at the site was postponed until the site was added to the SJCPHS-EHD pilot program RESNA continued the subsurface investigation during December 1991 We observed Woodward Drilling drill seven soil borings four borings were drilled to approximately 65 feet below ground surface (approximately 1 foot below ground water) and converted to vapor-extraction wells and three soil borings were drilled to approximately 75 feet below ground surface and converted to ground-water monitoring wells The ground-water monitoring wells were installed to evaluate ground water for possible dissolved hydrocarbons, and the vapor-extraction wells were installed to evaluate residual hydrocarbons in soil and evaluate whether remediation of hydrocarbons in native soil underlying the site is feasible by vapor extraction The groundwater monitoring wells were developed, purged, and sampled Ground-water samples collected from the wells were analyzed for gasoline and benzene, toluene, ethylbenzene and total xylenes Residual hydrocarbons were detected in soil samples collected from the borings and dissolved hydrocarbons were detected in water samples collected from the ground-water monitoring wells Vapor-Extraction Test A vapor-extraction test (VET) was conducted in December 30, 1991, to evaluate whether vapor extraction is a feasible means of remediating soil at the site Based on data obtained during the VET we concluded that an extraction rates of 30 cubic feet per minute from a vapor-extraction well will remove hydrocarbon vapor from soil in an area with a radius of approximately 25 feet, respectively Based upon the VET data, RESNA concluded that soil beneath the site can be remediated by vapor extraction Additional areas that will require remediation can be further defined and further specifications relative to the number and location of additional vapor-extraction wells can be evaluated when additional subsurface environmental investigations are performed Tank Removal ARCO's contractors are presently securing the appropriate permits from the SJCPHS-EHD to remove the tanks During the tank removal, a SJCPHS-EHD inspector, local fire department representative, and a RESNA staff geologist will be present at the site The contractor will first empty the tanks and dispose of the fluids in accordance with State 30003-4W L1