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<br />lo- <br />documented control over remova;i of dissolved Zn is Zn adsorption via carbonate precipir~ ~, <br />it seems imponant that the mechanism of carbonate precipitation be understood. <br />Please erplnitt in more specific geochemical terms how carbonate currently jornes in the <br />diatreme. <br />Please erplain hors the diatreme solutions can simttlrarteouslydfssolve and precipitate <br />carbonnteto sorb Zn. <br />M. GENERAL COMMENTS <br />The geology section indicates that most of the water derived from surface infiltration moves <br />downward through the diatreme via discrete fracture flow rather than by more homogeneous <br />porous media flow. The model for acid neutralization by carbonates in the deeper part of [he <br />diatreme however appears to rely on rather diffuse water movement through a somewhat <br />homogeneous porous media. <br />The operator should describe how potential acid generated in the upper part of the diatreme <br />will be neutralized 6y carbonates in the deeper part of the diatreme if groundwater moves <br />dominantly through discrete fractures rather than more homogeneously through the breccia <br />and other wtfractured rock.. <br />2. Appendix A. <br />The static test data in App A accompany no explanation of how samples were measured. It is <br />presumed for purposes of [his review that the tests measured the following: <br />a. total sulfur <br />b. sulfide sulfur <br />c, sulfate sulfer <br />d. organic (non-extractable) sulfur-calculated by difference <br />e. ANP by titration or some presumption of titrable alkalinity <br />]f these presumptions are incorrect, the Operator should it form the Division of such, providing <br />a explanation of the analytical procedures used for these analyses. <br />Proceeding as if the above presumptions are correct, it appears the methods may underestimate <br />AGP that might be generated in the field while overestimating field-available AMP. To wit: <br />AGP. Sulfate sulfur analyses include minerals such as the Ca-S0, family of minerals, which <br />would be non-acid generating, and the jarosite-alunite family of minerals -hydrous metal <br />sulfate evaporites -which could be variously acid-generating. <br />The Operator should describe the methods by which sulfate species were identified attd provide <br />evidence that the jarosite-alunite family ofinetal-sulfate /ndrnres were adequate/v accounted <br />for in the calculation ojAGP. <br />4. A.NP. The ANP method is not stated. For the system at hand, considering the mineralogical <br />composition of the diatreme described in Lindgren and Ransome, i[ is noted that ANP <br />calculations based on carbon and sulfur, whereby the carbon is total carbon assumed to be either <br />calcite or dolomite and rota{ sulfur values is assumed to be sulfide sulfur would be a preferable <br />meth~•d. <br />