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May 31, 1994 -3- 943-2720.010 Appendix B.2 (not included with this letter summary) contains all analytical data for the Carlton Tailings. It is noted that the TCLP analysis for Mercury (Hg) reported no exceedances in the three samples. The levels of mercury (Hg) in all three samples was <0.003 mg/L. Acid-Base Accounting The results of the acid-base accounting for the subsurface drill hole sample and the surface samples show that NNP of 43.86, 32.6 and 30.4 tons CaC0,/Kt exist in the Carlton Tailings material. In comparison, the pH of the three samples aze near-neutral to slightly basic and the alkalinity is very consistent between the three samples. Although this may be no surprise because the analyses were conducted on processed tailings, the Carlton Tailings have been exposed to environmental/meteoric conditions for many years and have had ample opportunity to react with on-site environmental conditions. The consistency between the subsurface drill hole sample and the surface samples (taken in different locations) lends credence to the homogeneity of the Carlton Tailings material. Table 8 presents the results of the acid-base accounting calculations and also presents the alkalinity and pH values for the three samples. Meteoric Water Mobility Discussion To check for potential reactions of the Carlton Tailings materials with meteoric conditions, the MWMP was conducted on four samples. Table 9 presents the results of analyses for the metals of concern, pH, alkalinity, and the two cyanide species. As the table presents, all metals of concern are considerably lower than the TCLP "Concentration for Toxicity". Appendix B.2 presents the full results of analyses. Additionally, the pH of the samples has retained a slightly basic characteristic, the alkalinity appears to be consistent and cyanide levels aze at, or below the detection limits. Cyanide Discussion Cyanide has been previously discussed in the context of the MWMP. As with the Ironclad tailings, WAD and total cyanide analyses were conducted for the "in-situ" samples (in the 1312 analyses) and for the "meteoric" samples. To allow direct comparison of all cyanide analyses Table 10 has been constructed. It should be noted that the table represents all cyanide analyses and therefore, both the solid phase, expressed as mg/kg and the liquid phase, expressed as mg/L are represented on Table 10. A total of seven samples were analyzed for the two cyanide species. Conclusions The geochemical laboratory test results indicate that the Carlton mill tailings should not contribute a source of acid or metals to surface or ground water. It is believed that the