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, <br /> ATERWORK <br /> G£OCHEMICAL•GEOTECHNICAL•ENVIRONMENTAL <br /> October 19, 1990 <br /> y, <br /> '-is. Darlene Reuss k <br /> San Joaquin County Public Health Services F �` ' <br /> N 1� <br /> Environmental Health Division <br /> P.O. Box 2009 t, <br /> cr,Q� l�. : <br /> Stockton, CA 95201 <br /> Re: 1990 Third Quarter Report-Tri Valley G 6200 <br /> Nowell Road, Thornton, CA. <br /> Dear Darlene: <br /> This letter report updates the activities a`c Tri-Valley Grower's <br /> Thornton plant during the thiid quarter of 1990. Activities <br /> during the quarter have included sampling for dissolved <br /> hydrocarbons and monitoring of groundwater. <br /> Groundwater monitoring conducted in July, August and September <br /> showed the water table dropped approximately 2 feet during the <br /> quarter (Table 1). The groundwater contour maps (Figures 1 and <br /> 2) continue to show a variation in direction and magnitude of the <br /> gradient (Table 1) as well as the static water levels (Table 2). <br /> I <br /> No discernible relationship between the gradient magnitude, <br /> gradient direction or water table elevation is apparent. <br /> However, the shallow groundwater system clearly is responding to <br /> influences other than natural oeasonal recharg,,. Recharge from <br /> irrigation or. the effects of pumping in the area are probable <br /> factors. <br /> Groundwater samples were collected from the six wells on <br /> September 18 and 19, 1990, for analysis of benzene, toluene, <br /> ethylbenzene, xylenes (BTEX) and total petroleum hydrocarbons as <br /> gasoline (TPHG), by EPA methods 8015/8020. in addition, MW1 was <br /> sampled for oil and grease by EPA method 5O3E. Gasoline <br /> hydrocarbons were reported in Mwl, MW2 and MW4. A general <br /> decrease in gasoline hydrocarbon concentrations were recorded in <br /> MW1 and MW4 and small amounts of hydrocarbons were again noted in <br /> MW2. Oil and grease concentrations were below detectable levels <br /> in MW1. The results are summarized in Table 3, and the <br /> -- <br /> ___-_ __laboratory_reportsand chain-of-custody are presented as <br /> ' Attachment 1. <br /> i <br /> 1710 MAIN STREET • ESCALON,CA 95320 • (209)838.3507 <br /> RENO.NV(702)788 8830 <br /> FRESNO.CA(209)222-3495 • <br /> i <br />