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Wm. J. Hunter & Associates 2220 Loma Vista Dr Registered Geologists Sacramento, CA 95825 Petroleum & Mineral Appraisers (916) 972-794,1 FAX (916) 172-1 683 4. November 21, 1996 - Steven Sasson, Sr RENS ' San Joaquin County PHS , Environmental Health Division f�J - P 0 Box 388 �a Stockton, CA 95201-0388 Ref Fourth quarterly groundwater monitoring report for 1401 W Fremont St , Stockton, Site Code 1782 We are enclosing a report covering the fifth sampling event at the above site, Valley Wholesale Drug Co It includes the field logs, laboratory results of water analyses, and maps showing the hydraulic gradient (s) and approximate lines of equal concentra- tions of benzene, ethylbenzene, toluene, xylene, & TPHg based on the latest data The field work was done on November 5, 1996, by Del-Tech Geotechnical Support Services as directed by our office PLATE I shows the hydraulic gradient based upon the latest sampling It continues to be to the north/northwest at about 006 - /ft The water table has dropped an average of 69 , since the July sampling, to an average depth of 8 58 - bgl The results of the laboratory analyses of water samples taken from the three monitoring wells since monitoring began are shown on TABLE I MW-1 revealed a reduction in the amount of all compounds analyzed, benzene decreased from 1600 ug/L to 1540 ug/L since the July sampling event Ethylbenzene dropped from 830 ug/L to 530 ug/L; toluene from 860 ug/L to 558 ug/L, xylene from 2500 ug/L to 1280 ug/L, and TPHg from 7 8 mg/L to 7 64 mg/L In fact, concentrations of all components have decreased in the last two samplings from the highest readings in March, 1996 MW-2 has been below detection limits in the last three samplings MW-3 , which was ND an July, 1996, recorded detectable levels of BTEX & TPHg in the November test . MTBE had not been detected in any of the wells during the last two sampling periods, and that analysis will be discontinued PLATES II through VI show the approximate lines of equal concen- trations of BETX & TPHg based upon the November, 1996 laboratory results The limits of the plune have been well defined to the east by MW-2 , and reasonably well to the south by MW-3 & SB-2 & SB-3 However, the limits to the north and west have not been fully defined, which is the direction of groundwater flow 1