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19 February 1997 <br /> AGE-NC Project No 95-0105 <br /> ' Page 2 of 4 <br /> ' standing water A minimum of three well volumes of water were removed from each well ten <br /> gallons of water were removed from MW-1, MW-2, MW-3, MW-5 and MW-6, twelve gallons of <br /> water were removed from MW-4 Ground water parameters were measured at two-gallon intervals <br /> using an ICM water analyzer, until temperature, pH and conductivity had stabilized (see Appendix <br /> A) Purged water was stored on-site in labeled, 55-gallon DOT-approved drums <br /> i23 COLLECTION OF GROUND WATER SAMPLES <br /> , <br /> Water samples were collected from each well using a new disposable plastic bailer Each water <br /> sample was transferred into two 40-m1 VOA vials containing 0 5 ml of 18%hydrochloric acid as a <br /> sample preservative and one I-liter amber bottle After collection,the samples were properly labeled, <br /> placed in a chilled container and transported under chain-of-custody to Alpha Analytical <br /> Laboratories (AAL) Each sample was analyzed for total petroleum hydrocarbons quantified as <br /> gasoline and as diesel (TPH-g and TPH-d), and for volatile aromatic compounds (benzene, toluene, <br /> ethylbenzene and total xylenes BTE&X) with methyl tertiary-butyl ether (MTBE) in accordance <br /> with EPA methods 5030/8015m and 602, respectively <br /> 3 0. FINDINGS <br /> ' 3 1 GROUND WATER GRADIENT AND FLOW DIRECTION <br /> ' The elevation of ground water in each well was calculated by subtracting the ground water depth <br /> from the surveyed casing elevation(Table 1) The casing elevation of each well had been previously <br /> surveyed relative to a City of Tracy bench mark <br /> ' Ground water elevations at the site ran _ <br /> ranged from 22 OS feet m MW b to 23 15 feet in MW-1 Between <br /> September and December 1996, ground water elevation decreased an average of 1 3 feet at the site <br /> ' The ground water flow direction conforms to the regional ground water flow direction and to the <br /> documented local flow direction, both of which are toward the north A low ground water elevation <br /> was calculated at the location of well MW-4,this is likely caused by an error in filed measurements <br /> and was not reflected in this quarters relative ground water elevation contours The ground water <br /> flow direction is depicted in Figure 3 -Relative Ground Water Elevation <br /> 3 2 PETROLEUM HYDROCARBON-IMPACTED GROUND WATER <br /> TPH-g was only detected in monitoring well MW-4, at a concentration of 11 000art <br /> p s per billion <br /> (ppb, reported as micrograms per liter) Benzene,toluene,ethylbenzene and xylenes were detected <br />