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... - "-_. .._" ia~u. ..125 __. ~.;:;! Jen~~3 22 ~diatreme however appears to rely on rather dlJfuse water movement through a somewhat ;,homogeneous porous media. ,. :;r „ ': '-`The operator should describe how parenrial acid generated rn the upper pan of the diarreme +Will be neutralized by carbonates in the deeper parr of the drmreme if groundwater moves `dominantly through discrete fractures rather than more homogeneously through the breccia . and other urll'racrured rock. Response: The.assumption of diffuse water movement (rather than fYacnue controlled) was not Intended and is likely.not the case. The carbonate mineralization is slate-stage hydrothermal evem that was concentrated along fractures, as evidenced by the vein-like swcture of carbonates at depth. Although the infiltration is concentrated along fractures, so too are the carbonate minerals, thus providing excess neutralization along the Very flow paths the tow pH water is likely to travel. The smaller, tighter fractures also represent the "closed" system described above for the build-up of carbon dioxide gas pressure,, as confined by hydrostatic pressure. 2. )"Appendix A. ~77re static rest data in App A accompany no explanation of how samples were measured It is "presamed for purposes of this review that the tests measured the following: ' ':a. total sulfur `'b. sulfidesuUur . c. sulfate sulfur d. organic (non-extractable) sulfur-calculated by d~erence e. ANP by titrntion or some presumption of titrable alkalinity i)lf these presumptions are incorrect, the Operator should Inform the Division of such, providing `id ezplanatton of the analytical procedures used for these analyses. Response: Static test analyses used the 5obek et al (1978) method for troth sulfur fractionation and ANP determinations. Consequently, the assumptions stated by the OMLR are valid 3. `Proceeding as if the above presumptions are correct, it appears the methods may underestimate 'AGP that might be generated in the field while overestimating field-available ANP. To wit: "'AGP. Sulfate sulfur analyses include mincraLr such as the Ca-SO~ family of minerals, which `would be non-acid generating, and the jarosite-alunite family of minerals- hydrous metal sulfate evaporlres • which could be vartously acid-generating. 'The Operator should describe the methods by which sulfate species were idenr1/ied and provide evidence that the jarosite-alunite family of metal-sulfate hydrates were adequately accounted 'for in the calculation ofAGP. Response: The,end member phases of jarosite (containing Fe) do produce small amounts of acid during dissolution (from hydrolysis of fearic iron). However, taken as a whole, the jar^osite-alunits family of metal-sulfate hydrates produces small amounts of acid compared to pyrite oxidation. Published data on Cripple Creek show that the majority of sulfate mintaals in the diatreme are gypsum and anhydrite, which ate non-acid generating sources of sulfate sulfur (Lindgren and Ratuome, 1906). ~. The buUt of jarosite is known to report to the'tesidual fraction" (also referred to erroneously as the "organic ftaction'~ In standard AGP sulfur analyses (Jennings and Dollhopf, 1995). However, as shown