1996-05-23_REVISION - M1977378 (2)

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-d W'i' 23 'ab 05: 3oPf 1 L I'�' r 1I r IEPALS_GEOL OG, P. 1 5TATE OF COLORADO DIVISION OF MINERALS AND GEOLOGY C)epartment of Natural Resources 1313 Sherman Sr, Room 215 De over,Colorado 80203 Phone:%31 866-3567 i0v FAX.(30,)832.8106 DEPARTMENT OF NATURAL RESOURCES Roy Romer Governor DATE: May 23, 1996 Ui�vtivc D;hh[,d ,NIM,,ier 8 1.o,,1; T0: Allen Sorenson Division Director ✓ FROM: Harry Posey ��'� RE: TR-19, American Tunnel, Permit No. 1v1-77-378 My revi w of the American Tunnel TR-19 application focused on the geochemical aspects of the injection fluid and their potential consequences• It is evident that injection of a high alkalinity solution is tied to EPA's recommendations. The injection of such fluid will have positive ramifications as long as the injection fluid mixes with other water in the mine pool or with water in pore spaces and fractures above the mine pool during resaturation of the drained rock volume. If the alkaline injection water fails to mix with these waters, it will itself dissolve the host rock and release their constituents to the fluid until the fluid is neutralized. I spoke with Larry Perino about the potential for fluid mixing and he is convinced that relatively effective mixing will be achieved. The path between the injection point and the developing mine pool will be a fairly tortuous one; other extant fluid will be traversed along the way; and the chances for mixing he says seem good. Even if the alkaline injection fluid does not mix well with the mine pool, it is not likely to matter overall as the addition of alkali is a bonus to the ultimate mine pool,-and the Sunnyside/State settlement agreement does not depend for its success on the addition of alkali. Mr. Perino indicated that the choice of alkaline material is currently still undecided, but that the choice is weighing heavily in favor of lime as there may be temperature problems with caustic soda and because caustic is more dangerous to handle. I considered the potential environmental effects of Na - not due to a spill of process material but due to eventual seepage from the mountain - but dismissed these concerns upon learning that the first likely point of agricultural use of the potential seep water would be some several tens of miles downstream. Hi-h Na concentrations might be of concern for soils and agricultural well being, but I understand from you and Mr. Perin that the potential seep water that may reach surface streams is many miles downstream, and that there are numerous 1