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1401 FREMONT, STOCKTON FILE' COPY <br /> VALLEY WHOLESALE DRUG <br /> PAGE 2 <br /> PHS/EHD has reviewed Fourth quarter 1999 groundwater monitoring report dated <br /> February 14, 2000 prepared by Wm.J. Hunter & Associates. Analytical results of the <br /> groundwater sample of Monitoring well #1 (MW-1) were 2,700 parts per billion (ppb) <br /> of Total Petroleum Hydrocarbon as gasoline (TPH-g), and 95 ppb of Benzene, 11 ppb <br /> of Toluene, 110 ppb of Ethyl-Benzene, and 62 ppb of Xylenes (BTEX collectively). <br /> The Benzene concentration in a groundwater sample was highest at 4,700 ppb in <br /> March 1996. The Benzene concentration in groundwater was 230 ppb in July 1999. <br /> The extent of the groundwater plume is not defined. It is unknown if the reduction in <br /> concentration of the contamination detected in groundwater samples collected from <br /> MW-1 is the result of plume migration and dispersion or natural attenuation. As stated <br /> in the letter dated February 17, 2000, PHS/EHD again disagrees with-this report's <br /> conclusion that additional investigative work is not justified. PHS/EHD agrees with <br /> the report's recommendation to reduce sampling to semi-annual (twice a year) at this <br /> time. Sampling may return to a quarterly schedule after additional investigative work <br /> has been completed. <br /> If you have any questions, please feel free to.contact Jeffrey Wong at (209) 468-0335. <br /> Donna Heran, RENS, Directors <br /> Environmental Health Division <br /> C, <br /> Cts' <br /> Jeffrey Wong , REHS ZLgoare�tagoritV <br /> LOP/Site Mitigation Unit IV Supervisor <br /> c: RWQCB, Central Valley Region — Marty Hartzell <br /> c: Wm.J. Hunter & Associates <br />