ARCHIVED REPORTS XR0001328 - Laserfiche WebLink

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Working to Restore Nature I volatile organic compounds, and polychlorinated biphenyls were not detected in the samples analyzed; however, total extractable hydrocarbons were detected During drilling on April 28, 1992, approximately 5 gallons of gasoline were released from a fractured product line between the dispenser islands and the underground tank cavity Results of the initial I assessment of the release were reported in our second quarter 1992 status report and addendum work plan (RESNA, August 11, 1992, Report 31009-6) Dissolved gasoline hydrocarbons were detected in water samples coll eed from the three wells Purgeable halocarbons were not detected, except for 1,2-dichloroethane which was detected in monitoring well MW-2 Fecal and total coliform bacteria were not detected in the sample collected from well MW-3 In January 1993, RESNA observed drilling of seven soil borings and the installation of two groundwater monitoring wells and four vapor extraction wells. Results of this assessment were reported in our first quarter 1993 status report (RESNA, June 9, 1993, Report 31009- 7) Analytical data indicated that hydrocarbons present in soil below 26 feet and in groundwater were probably from an offsite source Therefore, ARCO requested that an investigation of soil and groundwater be performed offsite and upgradient of the ARCO station to evaluate whether hydrocarbons were present upgradient of the site SUPPLEMENTAL INVESTIGATION 1 Field Work On October 6 and 7, 1993, a RESNA field geologist observed Westex Drilling of West M Sacramento, California drill two offsite soil borings (B-20 and B-21) Borings were drilled between 50 to 53 feet below surface grade (bsg) and converted to groundwater monitoring wells (MW-6 and MW-7) Groundwater was encountered at approximately 36 feet bsg Our field methods are described in an attachment to this report The geologist coilected soil samples from the borings at approximately 5-foot intervals for possible laboratory analyses and to characterize the geology beneath the site Samples were logged using visual and manual methods and classified according to the Unified Soil Classification System (Plate 3) Sediments encountered are shown on the Logs of Borings (Plates 4 through 9) On October 8. 1993, a technician from RESNA developed wells MW-6 and MW-7 Water samples collected after well development did not contain floating protect or product she�ei On November 1, 1993, at the request of ARCO, purge water was removed from the site by IWM of Pleasonton California Tom O Morrow Inc of West Sacramento California, a licensed land surveyor (California Land Surveyors 3275) surveyed the wells on October 20, 1130ccarl31009-4 2