Laserfiche WebLink
Applegate <br />Group, t~~. <br />June 19, 2007 <br />Ms. Erica Crosby <br />Senior Environmental Protection Specialist <br />Division of Reclamation Mining-and Safety <br />1313 Sherman Street, Room 215 <br />Denver,. Colorado 80203 <br />REC~I~~® <br />!JUN Z 2 2007 ~ <br />Division of Recfanlation, <br />Mining and Safety <br />v <br />RE: Timnath Pit (M-1999-050), Technical Revision 02 Adequacy Review Questions <br />Response ~/ <br />z~ <br />Deaz Ms. Crosby; <br />This letter is in response to the adequacy review comments dated June 11, 2007. The two <br />comments aze addressed below. <br />There was a discrepancy between the approved mine plan map and the mine plan map <br />submitted with the TR request. The map submitted with the TR request is accurate. The <br />area currently covered by,the ponds was mined through as part of the mining plan. The <br />ponds were created as part of the reclamation. This is why they were only shown on the <br />reclamation plan map. <br />2. The original reclamation plan discussed a dewatering trench to be located along the <br />north edge of the site. As mining progressed it became appazent that the open trench <br />system for handling the groundwater. was becoming a nuisance to the mining process. It <br />was determined that a French drain system could perform the same task and take up a <br />significantly smaller surface azea. <br />The open ditch that was functioning before replacing it with the French drain was at a <br />depth of 8 feet. Therefore the pipe would be buried approximately 8 feet deep. This <br />appeazs to be the level needed to intercept the water from entering the mining without <br />altering the ground water elevations. The installed pipe was 12-inch diameter A-2000 <br />perforated pipe with Y< inch diameter holes. The holes were aligned in pairs <br />approximately 30 degrees from invert space pairs 12-inch off center longitudinally. One <br />inch diameter gravel surrounded the pipe a minimum of 6 inches below the invert and a . <br />minimum of 18 inches above the top of pipe to help filter the water into the perforated <br />pipe. MIRAFI Geotex6le membrane was wrapped azound the gravel pack. Native <br />material was then used to backfill above the constructed drain to bring the land to existing <br />grade. The native material consisted of fines and some cobles. A standazd detail has <br />been included. The attached reclamation plan also shows the correct detail for the French <br />drain. <br />1499 West 120th Avenue, Suite 200 (303) 452-6611 • Fax (303) 452-2759 <br />Denver, Colorado 80234-2759 - www.applegategroup.com <br />