SITE INFORMATION AND CORRESPONDENCE

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Statement of Work Memorandum -3- 6 May 1992 DDRW, Tracy specific general minerals constituents, like metals, may be reduced after one or two sampling rounds. Table 7 indicates that ground water samples collected from many of the monitor wells will be analyzed for constituents currently monitored under WDRs Order No. 90-275. Samples from the following monitor wells are required to be analyzed for volatile organic constituents (VOCs) (Method 601) , semi-VOCs (Method 602), total petroleum hydrocarbons (TPHs) (Method 418.1) , organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs) (Method 608) , heavy metals (Method 6010) , arsenic (Method 7060), mercury (Method 7471) and selenium (Method 7740) : LM-15 LM-28 LM-29 LM-30 LM-49 LM-50 LM-53 LM-62 MW-1 MW-2 MW-3 MW-4 MW-5 Analysis for VOCs, semi-VOCs, TPHs, OC pesticides and PCBs and heavy metals appears to be redundant with what is required in the WDRs. Continued analyses for these contaminants is unnecessary and should be eliminated, unless the existing data from the 1991 quarterly monitoring reports indicate that these particular contaminants were confirmed as present in these monitor wells. Table 7 indicates that analyses using Method 8240 (624) will be performed on some of the monitor wells. This proposal appears to be a carry-over from the WDRs. It is unnecessary to continue to analyze ground water samples using this method if the samples will be analyzed using Methods 601 and 602. In general , this method should be eliminated from the quarterly monitoring program, unless the 1991 quarterly monitoring data indicate that a particular constituent is present in a particular well and was not detected using either Methods 601 and/or 602. However, ground water samples from newly installed monitor wells may need to be analyzed using Method 624. Table 7 indicates that OP pesticides and PCBs and TPHs are to be analyzed in many of the monitor wells. Analysis for these constituents are only necessary if the monitor wells are down gradient from a UST or WMU containing these types of wastes and if it is determined that ground water has been impacted. Once the site-wide investigation of USTs and WMUs is conducted and ground water impacts are confirmed, analyses for these parameters may be eliminated from the monitoring program in areas which have not been impacted. Page 8. Sections 3.10.6 and 7 discuss monitor well redevelopment for up to 43 monitor wells with an average depth of 30 feet and 12 monitor wells with an average depth of 75 feet. It is assumed that the number of wells may be reduced if any of the monitor wells are deeper than 30 or 75 feet. The SOW should clarify the total linear feet available for redevelopment. Page 10. Section 4.6 indicates that minutes of meetings will be provided to the Contracting Officer. If the regulatory agencies are in attendance at the meeting, the minutes of that meeting should also be provided to the agencies.