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Waste Management Unit Report -2- 10 September 1991 <br /> DDRW, Tracy <br /> For those WMUs in which a monitor well is to be installed and where the <br /> samples are to be analyzed for inorganic constituents, the ground water <br /> samples should be analyzed for general or standard minerals rather than for <br /> specific inorganic parameters such as sulfates, nitrates, TDS and pH. The <br /> cost for a general minerals analysis is not significantly greater than the <br /> cost for several individual inorganic parameters. The resultant analytical <br /> data for general or standard minerals may be used for a wider variety of <br /> purposes such as for determining cleanup levels, methods of disposal and for <br /> the operation of the interim remedial measure (IRM) . <br /> b. The number and depth of the soil borings samples were not specified for each <br /> WMU. In general , a minimum of three soil samples should be collected in the <br /> unsaturated zone: one at the base of the WMU or in the upper one foot below <br /> the base of the WMU, one sample from just above the ground water table and the <br /> third sample from between the other two soil samples. The ground water table <br /> at the DDRW, Tracy site is between 15 and 40 feet below ground surface (bgs) . <br /> Therefore, a minimum of three samples should be adequate to define the <br /> vertical extent of contamination and to approximate depths for potential <br /> removal actions. <br /> c. The Report indicates that samples are to be analyzed for total petroleum <br /> hydrocarbons (TPH) , but does not specify which fraction of the TPH will be <br /> analyzed. Future soil and ground water samples need to be analyzed for both <br /> the light and heavy fractions (gas and diesel , respectively) of TPH. In <br /> addition, if the WMU contained waste oils, then analyses for oil and grease <br /> (0&G) should be included. In general , for those WMUs which in which fuels <br /> and/or oils were disposed, the soil and ground water samples should be <br /> analyzed for TPH, gas and diesel , 0&G and the Environmental Protection Agency <br /> (EPA) Method 602 for benzene, toluene and xylene (BTXs) . <br /> d. The Report indicates that samples are to be analyzed for pesticide compounds. <br /> For those WMUs in which pesticides may have been disposed, the samples could <br /> be analyzed for total concentrations using the California Department of Food <br /> and Agriculture (CDFA) Multi Residue Screen. This method will provide a wider <br /> screening of potential pesticides rather than specific analyses for <br /> organochlorine pesticides (Method 8080) , organophosphate pesticides (Method <br /> 8140) and carbamate pesticides (Method Modified 632) . The detection limits <br /> for the Multi Residue Screen are equivalent to detection limits for the <br /> different EPA Methods. <br /> If the shallowest soil samples (that is, the samples taken from the base of <br /> the WMU) , indicate that there are only one type of pesticides present (such as <br /> organochlorine pesticides, the most persistent type of pesticides) , then the <br /> types of pesticides to be analyzed for in the deeper soil samples could be <br /> reduced. Because the highest concentrations of pesticides are anticipated to <br /> be found in the shallowest samples, the analytical results from the shallow <br /> soil samples could be used to determine what analyses should be performed on <br /> the deeper soil and ground water samples. The deeper soil samples may be held <br /> up to 14 days pending the analytical results of shallowest soil samples. <br /> e. The Report indicates that priority pollutant metals will be performed on <br /> samples. Instead of performing analyses for priority pollutant metals on soil <br /> samples, analyses for Title 22 metals should be performed on the soil and <br />