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WATERWORK <br /> GEOCHEMICAL o GEOTECHWAL a ENVIRONMENTAL <br /> 0E0 5 � R!� <br /> November 20, 1989 <br /> Ms. Darlene Reuss <br /> San Joaquin County Public Health Services <br /> Enviromental Health Division <br /> P.O. Box 2009 <br /> Stockton, CA 95201 <br /> Re: Thiru Quarter Report-Tri Valley Growers_.,-:)6200 Nowell <br /> Road, Thornton, CA <br /> Dear Darlene: <br /> This letter report updates the activities at Tri-Valley Grower's, <br /> Thornton plant during the third quarter of 1989. It also <br /> addresses the questions and comments presented in the letter from <br /> your office dated July 27, 1989. Activities during the quarter <br /> have included sampling for dissolved hydrocarbons and monitoring <br /> of groundwater. <br /> Groundwater monitoring conducted in August and September showed <br /> the watertable dropped approximately 1.5 feet during the quarter <br /> (Table 1). The groundwater contour maps (Figures 1 and 2) <br /> illustrate a southerly gradient at an . approximate magnitude of <br /> 0.018 ft/ft. This is an increase in magnitude A-nd a change from <br /> the westerly direction observed in April. There aro a number of <br /> possible reasons for these observed changes, howair_,, they must be <br /> evaluated over a series of monitoring events. <br /> Groundwater samples were collected from the six wells. on <br /> September 19, 1989 for analysis of benzene, toluene, <br /> ethylbenzene, xylenes (BTEX) and total petroleum hydrocarbons as <br /> gasoline, by EFA methods 8015/8020. In addition, MW1 was sampled <br /> for oil and grease by EPA method 503E. Low levels of <br /> hydrocarbons were reported in MW2 and MW6 for the first time. <br /> The levels in MW4 continue to decline except xylene which <br /> increased slightly. The oil and grease concentration in MW1 <br /> remained the same. The results are summarized in Table 2, and <br /> the laboratory reports and chain of custody are presented as <br /> Attachment I. <br /> The hydrocarbons detected in 'MW2 and MW6 are unexpected as MW6 is <br /> -- -- ---- - - -- - -----up-gradient--and MW3 <br /> - which is-between-MW4 -and-MW2 -has previously <br /> reported non-detected levels. Sampling or laboratory error could <br /> be the cause of these low levels. During next quarterly <br /> 1710 MAIN STREET • ESCALON.CA 95320 • (209)83&3507 <br /> FRESNO.CA(209)222-3495 a RENO,W(702)78B-6830 <br />