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June 29, 1988 <br /> ("1 <br /> AGS Job No. 86091-6 <br /> Page 2 <br /> FSamplesoffater from the air-fluid interface were <br /> tial water levels measurements in the <br /> monitoring wells. These samples were collected for subjective <br /> analyses by lowering a Teflon bailer approximately halfway <br /> through the interface. The bailer was then retrieved, and the <br /> water sample was examined for floating product, sheen, and other <br /> subjective evidence of hydrocarbon contamination. 6o floating <br /> Product, product sheen, emulsion, or odor was noted in samples <br /> from the monitoring wells. Results of these and previous <br /> subjective analyses are presented in Table 1. <br /> Monitoring wells Mw--1, MW-2, and MW-5 are 4-inch-diameter wells, EE <br /> and were purged prior to sampling with an electric submersible 1 <br /> Pump. Sixty to 75 gallons of ground water were removed from each <br /> well. Well MW-4 is a 2-inch-diameter well, and 30 gallons of <br /> ground-water were purged from it with an air-lift Pump prior to <br /> sampling. After purging, samples were collected by lowering a <br /> clean Teflon bailer through the air-water interface. The water <br /> was then transferred to laboratory-cleaned, 40-milliliter glass <br /> volatile organic analysis vials. A Chain of Custody Record was <br /> initiated in the field by the sampler and accompanied the samples <br /> ` to Applied GeoSystems' analytical laboratory in Fremont, <br /> California. A copy of this record is attached. <br /> The samples were analyzed for total petroleum hydrocarbons (TPH) <br /> by the Environmental Protection Agency (EPA) Method 801s <br /> (modified for gasoline) , and for the volatile hydrocarbon <br /> constituents berp:ene, ethylbenzene, toluene, and total xylene <br /> isomers (BETX) by EPA Method 602. Applied GeoSystems' laboratory <br /> is certified by the state of California for these analyses. <br /> Copies of the laboratory Records of Analyses are attached. <br /> The results of the laboratory analyses, summarized in Table 2, <br /> indicate that the concentration of benzene in ground water taken <br /> from monitoring wells MFaT-1, MW-2, and MW-4 exceeds the maximum <br /> level for drinking water recommended by the California Department <br /> of Health Services (DHS) . The concentration of the other <br /> t volatile constituents in these wells are below the maximum levels <br /> for drinking water recommended by the DHS. The concentration of <br /> all volatile constituents in ground water from well MW-5 are very <br /> low (below detection limits except for toluene) , suggesting that <br /> contamination of ground water by dissolved volatile constituents <br /> __(BETR) i - <br /> s_restricted--to--thevicinity-of the-tank-cavity, With _ <br /> T <br /> the exception of the benzene concentration in well MW-4, the <br /> concentrations of all hydrocarbon constituents in ground water <br /> from all wells has decreased since the last sampling event. <br /> • <br /> Agol ear 4GOOS stems <br />