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~~~; CLIMA)C MOLYBDENUM COMPANY Henderson Operations / <br />L~_~ A Subsidiary of Phelps Dotlge Corporation P.O. Box 68 <br />Empire, Colorado 80438 <br />(303j 569-322'1 <br />Fax [303) 569-2830 <br />RECEI~IED <br />Apri19, 2002 <br />Certified Mail No. 7099 3220 0005 0948 6738 APR 1 t 2002 <br />Mr. Allen C. Sorenson Division of Minerals and Geology <br />Reclamation Specialist p -I ` / Z <br />Division of Minerals & Geology ~>d c ~ ~Q 51 vp~ 5 Q !1" f 4y° a SO< ( t n ~C~i/t <br />Department of Natural Resources <br />1313 Sherman Street, Room 2l5 <br />Denver, CO 80203 <br />RE: HENDERSON MINE, PERMIT NO. M-77-342, Revision No. TR-8 / <br />Dear Mr. Sorenson: <br />This letter follows up our phone conversation last Friday regarding Henderson Mine's (Henderson) request <br />to finalize Technical Revision No. 8 (TR-8) to Permit No. M-77-342. This TR would allow for the disposal <br />of sludge generated from Henderson's Urad water treatment plant into Pond 1.2 (pond) located at the <br />minesite. At this point the Division of Minerals and Geology (DMG) has granted Henderson approval for <br />TR-8, conditional on Henderson developing a sludge placement plan that would protect the pond liner from <br />damage during sludge deposition operations. Based on our phone conversation Friday, it is our <br />understanding that DMG is satisfied Henderson's plan to accomplish this. Below is a description of the <br />plan, which is organized for your convenience, as it pertains to specific issues previously raised by DMG. <br />POTENTIAL FOR ROCKS TO BE INADVERTANTLY MIXED INTO SLUDGE <br />Consistent with DMG's recommendations, Henderson agrees to adequately purge rocks from sludge <br />moving equipment that is also used for other earth moving jobs prior to using the equipment in sludge <br />moving operations. The Urad impoundments from which the sludge is loaded are also designed to prevent <br />the introduction of rocks into the sludge. These impoundments are constructed with a bottom layer of <br />screened material that provides crock-free barrier between the sludge and impoundment bottoms. Loader <br />operators are instructed not to work below this interface to preserve the protective layer and prevent <br />digging up rocks. Additionally, as described in more detail below, sludge transported from the Urad <br />impoundments is stockpiled in a concrete secondary containment area. Henderson agrees to control this <br />sludge stockpile area, through ongoing monitoring and inspection, to eliminate the risk of rocks being <br />mixed with the sludge prior to its deposition into the pond. Finally, sludge placement will be conducted <br />only by personnel who have been trained and instructed in the proper performance of this work, with <br />special attention given to preventing rocks from being commingled with the sludge. <br />PLACEMENT OF EARTHMOVING AND COMPACTION EQUIPMENT ON POND LINER <br />The pond is lined with a 40 Mil HDPE Geomembrane liner. In the opinion of the liner supplier and <br />installer, Colorado Lining the liner will withstand the force of earthmoving equipment described in the <br />TR-8 application provided the liner is protected with 12 to 14 inches of fill material. Specifically, it is <br />Colorado Liner's opinion that 12 inches of fill would provide adequate protection for areas over which <br />equipment is moved infrequently; and that 24 inches would be adequate for areas over which equipment <br />frequently travels. Based on this advice, Henderson agrees not to move any equipment onto lined aeeas of <br />the pond prior to placement of at least 24 inches of fill on the liner. Additionally, necessary measures will <br />