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9 <br />tailings pond sample (RCG-SU) is used as a spike or duplicate sample, 930346-007 will be <br />the Analysis I.D. in the Quality Control Report). All spike and duplicate analyses involving <br />samples from the second third-party monitoring met the required quality control criteria in <br />TR-006, except for the unfiltered Collection Pond sample, which was used for for QA/QC <br />spike analysis. <br />The sample requested to be used for a QA/QC spike analysis, the unfiltered collection pond <br />sample discussed above, was not listed in the original (05/01/93) Quality Control Report. <br />Therefore, it was impossible to determine what the spike amount or percent recovery were <br />for this sample. Core Labs was phoned, and they agreed that they had omitted this sample <br />from the Quality Control Report. An amended Quality Control Report (dated (06/10(43) <br />was sent which included results for the unfiltered collection pond spike analysis. The <br />amended report is also attached as Appendix D. <br />As requested, the unfiltered sample from the collection pond was used for a quality control <br />spike recovery analysis (see Appendix C, pg. 12). The analyzed concentrations for total <br />cyanide and WAD cyanide were 0.58 and 0.55 mg/1, respectively. The spike amount used <br />was 1.00 mg/I for total cyanide and 0.25 mg/1 for WAD cyanide. The final results after <br />spiking were 1.34 mg/1 tots] cyanide and 0.56 mg/1 WAD cyanide, resulting in a spike <br />recovery rate of 76% for total ryanide and 4% for WAD ryanide. According to TR-006, the <br />analyzed spike recovery value must be within 75-125% of the known value (AI~pendix A, pg. <br />75). The percent recovery for total ryanide barely met the quality control criteria, and the <br />percent recovery for WAD cyanide was of course entirely unacceptable. The low percent <br />recoveries for both total and WAD cyanide suggests that both total and WAD cyanide values <br />are suspect in the collection pond samples, and possibly for the tailings porld samples as <br />well. An interference caused by the matrix is likely, as suggested in the 3une 9, 1993 letter <br />from Core Laboratories (Appendix E). <br />Another filtered Collection Pond sample (laboratory ID # 930346-10, pg. 10 of the Amended <br />Quality Control Report, Appendix D) was used to perform a spike analysis. The recovery <br />on this sample was 104%, which indicates that filtered samples from the collect(on pond may <br />have fewer or less severe interferences than unfiltered samples. <br />Two strategies are recommended for improving the cyanide determinations ih the process <br />point samples: (1) send the samples to another laboratory or have Core Labs ufie alternative <br />ryanide methods; and/or (2) have Core Labs or another lab perform a series of experiments <br />to determine the cause of the analytical problem. A recommendation for tlhe analytical <br />experiments is to perform both total and WAD cyanide determinations on unfiltered <br />collection pond, upper tailings pond and lower tailings pond samples using the following <br />additional reagents or steps in the analytical method: NaAsO2 (to counteract oxidizing agents <br />in the sample); fatty acid extraction (the green precipitate may contain fatty acids); ethylene <br />diamine (to remove potential glucose interference); sulfamic acid (add only to total cyanide <br />method, to remove nitrite interference), and PbCO3 (to remove interference from sulfur <br />RCG/Hagler, Bailly, lac <br />