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iii iiiiiiiiiiiu iii <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1313 Sherman $I., Room 215 <br />Denver, Colorado 80203 <br />Phone: 13031 8663567 <br />FAX: 13031832-8106 <br />DATE: January 12, 1995 <br />TO: Jim Stevens, Btvice Humphries <br />FROM: James Dillie L~,~. <br />RE: Response to D/VM/O`Determination, San Luis Project, Permit No <br />II~~~ <br />DEPARTME[9T OF <br />NATURAL <br />RESOURCES <br />Roy Romer <br />Governor <br />lames 5. Lochhead <br />Executive Director <br />Michael B. Long <br />Division Dvttlor <br />M-88-112 <br />Pursuant to BMRI's response to the Division's DMO determination (see attached letter) <br />Ms. Sally Hayes states that the second and third reasons for DMO status are inaccurate. She <br />says BMRI is not extracting high sulphide ore nor have there been any indication of acid <br />mine drainage as a result of their extensive and on-going testing program. Ms. Hayes cites <br />data from two sections of the approved permit that, she says, substantiates BMRI's claims. <br />Bruce instructed me to review BMRI's response and, if the Division agrees with the <br />response, to send a revised DMO letter. First of all, reason number two of the DMO letter <br />states in part "high sulphide ore..." Ms. Hayes does not address this issue in her response. <br />She does say that "Section D.3.3.2 of the approved permit states that waste roc cL is neutral <br />to slightly alkaline" as her reason for disagreeing with reason number two of the DMO letter. <br />The ore (and part of the waste rock) at the San Luis Project is comprised of a sulphide <br />material. Whether this sulphide material is neutral, has acid generating potential; or has acid <br />neutralizing potential is not very clear. It is a sulphide and sulphides are capable of <br />generating acid waters under certain conditions. <br />Humidity cell test result data presented in Appendix F of the 1988 permit applilation would <br />imply that an acid producing condition is possible at the San Luis Project. Measured pH <br />values during weeks 8, 9, and 10 of the test period showed a decrease in value for several <br />samples. Since the pH was still declining during week 10 it is possible that a pH of less than <br />6 could be achieved if the humidity cell tests had been allowed to ntn for 20 weeks (instead <br />of 10). Specifically, pH values for weeks 8, 9, and 10 for unrinsed ore sample L.356.2-3.0 <br />were 7.58, 7.51, and 7.21. Values for rinsed ore sample L.356.2-3.1 were 6.79, 6.53, and <br />6.47. Waste rock samples L.356.0-1.0 and L.356.0-3.0 (Appendix F) that were analyzed in <br />1988 exhibited more acid neutralizing potential than acid producing potential (1:i.7 to 5.12 <br />and 1.8 to .6). However, the humidity cell tests for these samples were only nm for 8 <br />weeks which, according to Bill York-Feirn's comments (letter dated September 1, 1994), the <br />