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4 <br />23 SAMPLE PRESERVATION <br />As discussed above, all samples were unfiltered. Un5ltered groundwater samples were taken <br />so that metals and cyanide samples were comparable, instead of taking filtered metals <br />samples and unfiltered cyanide samples. All samples were checked after collection to ensure <br />that they were preserved to the proper pH. Cyanide samples were preserved with solid . <br />NaOH to pH >_12, and metals samples were preserved with nitric acid to pH <2. <br />3.0 SUMMARY AND ASSESSMENT OF ANALYTICAL ACTIVITIES <br />3.1 ANALYTICAL RESULTS <br />The field parameters and analytical results are displayed in Tables 2 and 3, respectively. A <br />discussion of any elevated concentrations or unusual results and comparDSOn to previous <br />results is provided below. <br />3.1.1 Surface Water <br />RS-5. The pH of Rito Seco was significantly higher than pH values in March, April, and <br />May 1993 and was appro~dmately the same as the pH measured in November 1992, <br />indicating that there may be seasonal pH fluctuations of over one pH unfit (6.42 to 7.96). <br />Total and WAD cyanide were again below detection (at 20 µg/1) at this location, as was <br />copper (at l0 µg/I). Iron concentrations (560 µg/1) were very similar to those measured <br />during the November 1992 third-party monitoring trip. Iron and pH may co-vary throughout <br />the year, with lower pH values being associated with elevated iron concentrations in the <br />stream. <br />3.1.2 Process Points <br />Total cyanide concentrations were once again highest in the collection impoundment and <br />were above detection in all process point samples. WAD cyanide concentrations were above <br />detection but below 1 mg/I in all process point samples and were lower than those measured <br />in May 1993. Acceptance criteria for laboratory duplicate analyses of total cyanide were not <br />met for either the upper or lower tailings impoundment samples. Core Laboratories reran <br />these samples for total cyanide but did so after the 14-day holding time had elapsed. The <br />QC problems associated with total cyanide concentrations make it difficult to assess whether <br />total cyanide concentrations are higher than WAD cyanide in October 1993. <br />doer Tailings Impoundment. Measured lab duplicate total cyanide concentrations in the <br />upper tailings impoundment were 160 and 260 µg/1. This results in a relative percent <br />RCG/Hagler Bailly <br />