7.2. Chemical Analysis

The documentation for nonradiological analyses is contained in the ESH-DA Chemistry Laboratory Procedure Manual. All samples for NPDES and groundwater are collected and analyzed in accordance with EPA regulations found in 40 CFR Part 136,²⁶ EPA-600/4-84-017,³⁵ and SW-846.⁹

Standard Reference Materials (SRM), traceable to the NIST, exist for most inorganic analyses (see Table 7.3). These are replaced annually. Detection limits are determined with techniques listed in Report SW-846⁹ and are listed in Table 7.4. In general, the detection limit is the measure of the variability of a standard material measurement at 5 to 10 times the instrument detection limit as measured over an extended time period. Recovery of inorganic metals, as determined by "spiking" unknown solutions, must be in the range of 75% to 125%. The precision, as determined by analysis of duplicate samples, must be within 20%. These measurements must be made on at least 10% of the samples. Comparison samples for organic constituents were formerly available from the EPA, but are now commercially available under the Cooperative Research and Development Agreement (CRADA) that exists between the EPA and commercial laboratories. In addition, standards are available that are certified by the American Association for Laboratory Accreditation, under a memorandum of understanding with the EPA. Many of these standards were used in this work. At least one standard mixture is analyzed each month; the results for 1995 are shown in Table 7.5 for VOCs and Table 7.6 for SVOCs. The recoveries listed are those required by the respective methods.

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