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9 3.1.4 Quality Control Samples Field and Rinse Blank. The field blank and rinse blank again used second-stage DI water from the BMRI laboratory. Total cyanide, WAD cyanide, calcium, and copper concentrations were all at or below detection in both the field and rinse blanks. The rinse blank had relatively high concentrations of sodium, but calcium concentrations were significantly lower than those measured in the May 1993 rinse blank. 3Z QUALITY CONTROL ANALYSES AND RESULTS Quality control results related to process point laboratory duplicates were discussed above in Section 3.1.2. The Quality Control Report is included as Appendix D of this summary report. Core Laboratories used a number of samples from the fifth third-party monitoring trip to perform spike and duplicate QA/QC analyses. The identity of the sample (e.g., M-9) is noted in Appendix D next to the analysis I.D. Core Labs was specifically requested to run QA/QC analyses on the process point samples upon receipt of the samplers. The following samples from the 5fth third-party monitoring trip were used for cyanide QA/QC spike analyses: upper tailings impoundment (total and WAD cyanide); lower tailings impoundment (total and WAD cyanide); collection impoundment (total and WAD cyanide); field blank (copper, zinc, sodium and iron); M-9 (total and WAD cyanide); and M-13 duplicate (WAD cyanide). The following samples were used for cyanide QA/QC duplicate analyses: RS-5 (copper, iron, zinc and sodium); upper tailings impoundment (total and WAD cyanide), lower tailing impoundment (total and WAD cyanide), collection impoundment (total and WAD cyanide); M-9 (WAD cyanide); and M-13 duplicate (WAD cyanide). All samples were unfiltered. Acceptable control limits for spike analyses is ±75-125% of the known value, and acceptable control limits for duplicate analyses is ±20%RPD. Spike analyses performed on the collection impoundment sample for both total and WAD cyanide were outside control limits (133% for both total and WAD cyanide). In the November l5, ]992 letter (Appendix E), Core Laboratories explains this high recovery as being related to the dilution necessary for the high color of the sample. Dilution of another aliquot of the sample prior to spike addition would have circumvented this problem. All other spike recoveries were within control limits. As discussed in Section 3.1.2, duplicate analyses for total cyanide performed on both the upper and lower tailings impoundments were outside of control limits. All other duplicate analyses were within control limits. The color dilution also explains a discrepancy between values reported in the Quality Control Report and the Analytical Report for the collection impoundment sample. The original total cyanide values for the collection impoundment and lower tailings impoundment samples (932003-4 and 932003-6, respectively -- see Quality Control Report, Appendix D, RCG/Hagler Badly