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~~ III IIIIIIIIIIIII III STATE OF COLORADO DIVISION OF MINERALS AND GEOLOGY Dep. rlmrm of Natural Resources I S I }Sherman SL, Room ?1 5 yk Ucnver, Colorado fl0'_03 Il ~ Y Fhunc U011866-}567 ~ II FAr. ~ ;q S1 713?-N 106 DEPARTMENT OF December 17, 1998 NATURAL RESOURCES Ann Beierle R°~Romr. Climax Molybdenum Company c°vrr"°r P.O. Box 68 wn,rs s. ~urnhrad Empire, CO 80438 Ececuuve Director Michael B. Long Division Director RE: Soil Salvage in Tailing Basin, Henderson Mine and Mill, Permit No. M-77-34? Dear Ms. Beierle: In a telephone conversation on December 10, 1998 we discussed soil salvage, stockpiling, and replacement requirements under the Henderson Mine and Mill reclamation permit and the Colorado Mined Land Reclamation Act. During [hat conversation you stated that Climax Molybdenum Company (CMC) is considering modifications to the currently approved topsoil-handling plan. Specifically bt:ing considered is a plan to abandon and inundate under tailing two topsoil stockpiles that are in the path of the expanding tailing pond, and a plan to discontinue soil salvage of remaining in situ soils in advance of tailing encroachment. Under such a plan, the average 12 inch topsoil replacement requirement o'+er [he tailing at the time of reclamation would be met by borrowing soils from areas located above the fin.tl tailing surface elevation. As we discussed, this plan, if submitted, would be rejected by the staff of the Division of Minerals and Geology (DMG). The basis for the staff's denial would be: Suitable plant growth medium in the area of the Henderson Mill is a scarce and valuat~le resource that should not be lost through inundation under the Henderson Mill tailing given that the ~Ipproved reclamation plan requires large volumes of plant growth medium for replacement on the tailing surface. The intent of the general assembly of the Colorado legislature through the enactment of the Mined Land Reclamation Act is the conservation of natural resources such as plant growth m?dium, referred to in the Act as topsoil (34-32-102(1) C.R.S.). Borrowing topsoil from locations outside the area of tailing inundation would create substantial additional acreage of disturbance requiring reclamation. Successful reclamation of this additional acreage, as measured against the revege[ation performance standards of Rule 3.1.10 of'the Regulations of the Mined Land Reclamation Board, would be difficult to achieve once the A-horizon topsoil had been removed to spread on the tailing. Essentially, considerable value from a reclama~:ion standpoint is derived from the microbial activity and nutrients that are present in abundance in near surface soil, and that diminish rapidly deeper in the soil profile. irreplaceable loss of the near surface soil by inundation under the tailing will result in a diminution in quality of the eventual reclamation of the site. It is a basic principal of natural resource conservation that in the construction of an impoundment, the earthen materials required for construction be salvaged to the full extent possible from the area to be inundated by the impoundment.