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Statement of Work Memorandum -2- 6 May 1992 <br /> DDRW, Tracy <br /> It is unclear what additional monitor wells are to be included in the list <br /> of 100 wells to be monitored. <br /> The list of 100 monitor wells apparently does not include any of the IRM <br /> monitor wells. These wells should also be included for monitoring since <br /> they do not duplicate any of the 100 wells. In addition, this section <br /> does not account for monitoring of any additional monitor wells or <br /> piezometers that may be installed as part of the underground storage tank <br /> (UST) or WMU investigations. Any wells installed as part of these <br /> investigations should be included in the site-wide monitoring program. <br /> This section also indicates that piezometers and monitor wells are to be <br /> presented in map form. A base map of all well locations, including <br /> piezometers, monitor, supply, extraction, injection and off-site private <br /> supply wells (those selected as part of the monitoring program) needs to <br /> be provided. In addition, a table summarizing all well construction <br /> information should also be provided. <br /> Page 5. Section 3.5. 1 states ground water samples are to be collected from monitor <br /> wells. It is unclear what the difference is between piezometers and <br /> monitor wells that prevents piezometers from being sampled. If a <br /> piezometer is located in an appropriate position from an UST or WMU, then <br /> the piezometer should be used to collect ground water samples, assuming <br /> that the diameter of the piezometer (two inches or greater) is wide enough <br /> to allow sample collection. <br /> The SOW does not appear to incorporate sampling of any new monitor wells <br /> that may be installed as part of the UST or WMU investigations. These <br /> wells should also be incorporated into the site-wide monitoring program. <br /> Page 6. Section 3.5.2 lists the analytical parameters in Tables 1, 3 and 7. Table <br /> 1 lists arsenic, chromium, mercury and selenium twice; once under the 7000 <br /> series and one under the 6010 series. Arsenic, lead, mercury and selenium <br /> should be analyzed using atomic absorption and therefore, should be listed <br /> separately from the other heavy metals. Table 1 also provides a list of <br /> parameters under general minerals. Carbonate should be added to this list <br /> as a parameter for an--lysis so that cation/anion balances can be <br /> calculated. <br /> Table 7 does not include analysis for general minerals. Although general <br /> minerals are generally not considered hazardous constituents, analysis for <br /> general minerals is needed to type the different water bearing zones, to <br /> determine background concentrations of each water bearing zone and <br /> ultimately to determine numerical Applicable or Relevant and Appropriate <br /> Requirements (ARARs) to comply with the Anti-Degradation Policy. High <br /> concentrations of minerals in ground water will also affect the operation <br /> and maintenance of the IRM and the method of disposal for the treated <br /> ground water. Ground water samples should be analyzed for general <br /> minerals for some monitor wells from each water bearing zone. Sample <br /> collection and analysis should be performed in one sampling round, with a <br /> second round, if necessary, for confirmation. Generally, analyses for <br />