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��ui■1A <br /> MAMA <br /> Working to Restore Nature <br /> recovery well, collecting and analyzing soil and groundwater samples for hydrocarbons, and <br /> performing a groundwater aquifer test and a soil vapor extraction test (Applied GeoSystems, <br /> November 20, 1990, Problem Assessment Report No 38009-2, and RESNA, December 8, <br /> 1992, Letter Report No, 38009-4) <br /> SUPPLEMENTAL INVESTIGATION <br /> Field Work <br /> On September 23 and 24, 1993, a RESNA field geologist observed Woodward Drilling of <br /> Rio Vista, California drill one offsite (B-14) and two onsite soil borings (B-16 and B-17) <br /> Boring B-14 was drilled offsite to 57-1/2 feet below surface grade (bsg) and converted to <br /> a groundwater monitoring well (MW-5), and borings B-16 and B-17 were terminated at 41- <br /> 1/2 feet bsg and converted to vapor extraction wells (VW-4 and VW-5) Groundwater was <br /> encountered in boring B-14 at 44 feet bsg Field procedures are presented in the <br /> attachment <br /> On September 23, 1993, a RESNA field geologist observed Westex Drilling of West <br /> Sacramento, California drill one soil borings at the site Boring B-15 was drilled in the <br /> station bay to approximately 41-1/2 feet below surface grade (bsg) <br /> or <br /> The geologist collected soil samples from the <br /> The at approximately 5-foot intervals for <br /> possible laboratory analyses and to characterize the geology beneath the site Samples were <br /> logged using visual and manual methods and classified according to the Unified Soil <br /> Classification System (Plate 3) Sediments encountered are shown on the Logs of Borings <br /> (Plates 4 through 12) <br /> Well MW-5 was developed on October 8, 1993 Water samples collected after well <br /> development did not contain floating product or product sheen Tom O Morrow Inc <br /> surveyed the wells on October 20, 1993 Water generated during development and drilling <br /> operations were stored in a DOT-approved 55-gallon drums pending disposal <br /> On September 24, 1993, our geologist collected soil samples (one composite of four <br /> samples) from the stockpiled soil for analyses to evaluate disposal options Drill cuttings <br /> from the borings were stockpiled onsite on plastic sheeting pending disposal <br /> Laboratory Methods and Results <br /> Select soil samples from the borings and the samples from the stockpile were analyzed for <br /> total purgeable hydrocarbons (equivalent to total petroleum hydrocarbons as gasoline <br /> [TPHgD with benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) distinction <br /> �� <br /> 1112if--,/3800¢4 2 <br />