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r <br /> IN _Zi <br /> Quarterly Ground-Water Monitoring October 19, 1989 <br /> Beacon Station No. 492, Manteca, California AGS 86102-4 <br /> Thground <br /> -water grounwater samples were analyzed for total <br /> yz purgeable hydrocarbons (TPH) as r <br /> gasoline, benzene, chlorobenzene, 1,4-dichlorobenzene, toluene, ethylbenzene, and total <br /> Xylene isomers using Environmental Protection AgenvI (EPA) Method 503.1 at BC <br /> + Laboratories, Inc., in Bakersfield, California (Hazardous Waste Testing Laboratory <br /> Certificate No. 102). The results of these analyses and previous laboratory analyses are <br /> summarized in Table 2. Copies of the Iaboratory Analysis Reports are attached. <br /> The results of the ,laboratory analyses indicate that TPI; as gasoline, benzene, toluene, and <br /> y ethylbenzene concentrations in the groundwater samples collected from the three wells <br /> were below the detection limits of the analytical methods used. 'the laboratory analysis of <br /> previous samples has given similar results for MW-2 and MW-3;however,the latest analysis <br /> of the sample collected from MW-1 shows a significant decrease of hydrocarbon <br /> contamination, <br /> S` ' Applied GeoSystems evaluated the ground-water gradient across the site by combining <br /> measurements of the static water level with the relative elevation of the top of the casing <br /> in each monitoring well. The relative elevation of the top of the casing in each well was <br /> previously evaluated with a Lietz/Sokkisha C3E Automatic Level. The measureme'ats of <br /> the static water levels were adjusted using the top of the casing in well MW-2 as a datum. <br /> These data are summarized in Table 3. The evaluated groundwater gradient was 0.001 and <br /> the flow direction was toward the east. The gradient was interpreted to be essentially flat. <br /> Applied GeoSystems recommends that monitoring of ground water at the site be continued <br /> E quarterly. The next sampling has been scheduled for the week of October 9, 1989. <br /> Copies of this report should be forwarded to Ms.Laurie Cotulla of the San Joaquin County <br /> Local Health District,Environmental Health Division, P.O.Box 2009,Stockton, California <br /> } <br /> R <br /> Y� <br /> f <br /> f <br /> : 2 <br />