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�Ilemorandun* <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION <br /> 3443 Routier Road Phone: (916) 361-5600 <br /> Sacramento, CA 95827-3098 ATSS: 8-495-5600 <br /> TO: Antonia Vorster V FROM: Gary Reents <br /> Senior Engineer / \ '� Area Eng;neer <br /> DATE: 2 September 1987 SIGNATURE: <br /> SUBJECT: MC CORMICK & BAXTEkREVISED WORKPLAN, SAN JOAQUIN COUNTY <br /> The subject workplan, dated July 1987, was submitted in response to the State' s <br /> (combined Regional Board and Department of Health Services) comments dated 3 July <br /> 1987. In addition to the revised workplan, CH2M Hill, consultants to Mc CormicK <br /> & Baxter (MB) , submitted responses dated 31 July 1987 to 14 of the State ' s <br /> comments with which they did not agree. <br /> I concur with all of MB's responses to the State's comments, except regarding the <br /> monitoring well sampling program, comment 19 in the State' s 3 July memorandum. <br /> Regarding the sampling program, I have the following comments: <br /> 1. Wells OS-1E and OS-3E should be included in quarterly monitoring until the "E" <br /> zone flow direction has been confirmed. The reported flow direction (no data <br /> has been submitted to the State) of northeast does not correspond to the known <br /> hydrogeologic conditions. After additional gradient data has been collected, <br /> a decision can then be made whether continued quarterly sampling of these <br /> wells is necessary. <br /> 2. Data from Wells DSW-2A and DSW-26 identify the eastern edge of the plume in <br /> the shallow aquifer. As such, these wells should be monitored quarterly to <br /> confirm the plume extent in this area with time. Since the shallow ground <br /> water on-site is in hydraulic contact with deeper ground water and is moving <br /> downward, high TDS and chloride values do not necessarily remove all concern <br /> for monitoring. <br /> 3. I agree the existing data does not warrant quarterly monitoring of the City <br /> Police well at this time. Monitoring of the Gold Bond wells, however, is very <br /> important . - The Gold Bond wells appear to be the controlling hydrologic <br /> influence in the area and have contained possible site contaminants based on <br /> past sampling data. Sampling of the appropriate Gold Bond wells will monitor <br /> for the leading edge of the contamination plume until the plume is defined <br /> with additional monitoring wells. <br /> GAR:ej <br />