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WEISS ASSOCIATES <br /> detergent and tap water, rinsed with tap water and then allowed to air-dry prior to sampling <br /> Plastic sheeting was laid on the ground near the well to prevent well sampling equipment from <br /> contacting the ground <br /> The results of the ground water analyses will be used to determine the appropriate <br /> disposal method for the waste water <br /> 2 4 ANALYTIC RESULTS FOR GROUND WATER <br /> Analytic results for the ground water are presented in Table 5 and the analytic reports <br /> are included as Appendix C Ground water samples collected from monitoring wells MW-1 and <br /> MW-2 adjacent to Vaults 1 and 6, respectively, were analyzed by gas chromatography/flame <br /> ionization detection (GC/FID)using a "DB Wax"megabore-type chromatographic column The <br /> ethylene glycol and propylene glycol analyses used a five point calibration curve to standardize <br /> the GC The method detection limit was 1 part per million (ppm) Ethylene glycol and <br /> rpropylene glycol were not detected in ground water samples from MW-1 and MW-2 <br /> Water samples from monitoring well MW-3, installed next to Vault 8, were analyzed for <br /> soluble total chromium, sodium and calcium by EPA Method 6010 inductively coupled argon <br /> plasma Soluble hexavalent chromium and chlorides were analyzed by colorimetric EPA <br /> Methods 7196 and 3252, respectively Ground water samples from monitoring well MW-3 <br /> contained total chromium and hexavalent chromium at 0 10 ppm and 0 11 ppm, respectively <br /> The hexavalent chromium results exceed the total chromium results due to the variability of <br /> the respective analytic methods The detected sodium,calcium and chloride concentrations are <br /> all below applicable health and/or aesthetic standards However,the only standard for sodium <br /> and calcium is their contribution to total dissolved solids (TDS) The sum of their constituent <br /> ' concentrations are below the TDS standard of 500 ppm <br /> 2 5 GROUNDWATER ELEVATIONS <br /> Top-of-casing elevations for the three monitoring wells and a former irrigation well were <br /> surveyed on March 1, 1991 by Ernest Smith of Stockton,California(California Registered Civil <br /> Engineer #15372) The datum elevation for the survey was a City of Stockton benchmark east <br /> of the intersection of Charter Way and Mariposa Road <br /> D lALL1331DWG1331R1MA1 WP Page 10 <br />