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WEISS ASSOCIATES v <br /> P. Hernandez / 20 July 1988 / Page 3 <br /> 21 Spike and duplicate recovery data: <br /> 3) Detection limits• and <br /> 1 Analysis sensitivities. <br /> 6. METALS ANALYSES <br /> The SJLHD has requested that we initially use the WET extraction technique to <br /> determine the soluble portion of the analyte in the soil samples. Therefore, page 8, <br /> paragraph 5 of the 1 May 1988 sampling plan (page 16, paragraph 5 of the enclosed <br /> revised sampling plan) is amended as follows: <br /> The samples from beneath Tanks 7 and 8 will be analyzed, using the Waste <br /> Extraction Test (WET) technioue, fQr soluble chromium (Cr) and copper (Cu) by atomic <br /> absorption (AA) with detection limits of 0.01 to 0.02 ppm. These samples will also bo <br /> analyzed for total sodium NA ¢y AA with I detection limit � 2 ppm and by <br /> colorimetric determination for sulfate with a detection limit of 10 ppm. Since sodium <br /> and sulfate are non-toxic. no STLCs have been established for these compounds. The <br /> samples will be reanalyzed for total Cr and Cusu ine ni ri gyri i estion NAD if the <br /> analytic results are above the Soluble Threshold Limit Concentration (STLC) for these <br /> compounds. If the analytic result is above the STLC for chromium the samples will be <br /> reanalyzed, using NAD, for total hexavalent chromium by EPA Method 7196, colorimetric <br /> determination. <br /> We should be able to begin the field work within two to three weeks of SJLHD <br /> approval of this revised site sampling plan. <br /> We appreciate the opportunity to provide hydrogeologic consulting services to <br /> Diamond Walnut Growers, Inc. Please call if you have any questions. <br /> Sincerely, <br /> Weiss Associates <br /> J Jo6ph P. Theisen <br /> Senior Staff Geologist <br /> JPT/ja <br /> F:\ALL\331DWG\33IL2JL8.DOC <br /> Encl.: Revised Sampling Plan <br /> cc: Bill Snavely, SJLHD <br />