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HIM <br /> 6 <br /> �e <br /> — . <br /> i <br /> r^' <br /> ATER ORK <br /> GEOCHEMICAL•GEOTECHNICAL•ENVIRONMENTAL <br /> April 19, 1990 �•9f ��e1t� <br /> VN <br /> Ms. Darlene Reuss L5 <br /> San Joaquin County Public Health Services �j y <br /> Enviromental Health Division �i�3• <br /> P.O. Box 2009 <br /> Stockton, Ca 95201 <br /> Re: 1990 First Quarter Report-Tri Valley Growers,-.2,6200 <br /> Nowell Road, Thornton, CA. <br /> Dear Darlene: <br /> This letter report updates the activities at Tri-Valley Grower's, <br /> Thornton plant: during the first quarter of 1990. Activities <br /> during the quarter have included sampli,ig for dissolved <br /> hydrocarbons and monitoring of groundwater. <br /> Groundwater monitoring conducted in January, February and March <br /> showed the watertable rose approximately one foot during the <br /> quarter (Table 1). The groundwater contour maps (Figures 1 and <br /> 2) illustrate a westerly gradient at an approximate magnitude of <br /> 0.006 ft/ft. A review of the groundwater elevation data back to <br /> September of 1987 (Table 1) shows considerable variation in bath <br /> the direction and magnitude of the gradient, as well as the <br /> static water levels. <br /> No discernible relationship between the gradient magnitude, <br /> gradient direction or water table elevation is apparent. <br /> Clearly, however, the shallow groundwater system is responding to <br /> influences other than natural seasonal recharge. 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 March <br /> 20, 1990, for analysis of benzene, toluene, ethylbenzene, xylenes <br /> (BTEX) and total petroleum hydrocarbons (TPH) as gasoline, by EPA <br /> methods 8015/8020. In addition, MW1 was sampled for oil and <br /> grease by EPA method 503E. Low levels of gasoline hydrocarbons <br /> were reported in MW1, MW3, MW4 and M146. Significant increases in <br /> gasoline constituent concentrations were recorded in wells 1, 3, <br /> and 6, while well 4 showed increases in some constituents and <br /> decreases in-others Oil and-Grease--levels in well...MWl...-have....--- _ <br /> 7710 MAIN STREET • ESCALOR CA 95320 • (209)B38-3507 <br /> FRESNO,CA(209)222-3495 • RENO,NV(702)788.6630 <br />