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~~. <br />• ~ • iiiiiuiiiiiiiiiiii <br />TR9PP8R ~ININR INC. <br />FEB 11 1991 <br />Mr. David A. Berry <br />Reclamation Specialist <br />CMLRD <br />1313 Sherman Street -Room 215 <br />Denver CO 80203 <br />February 5, 1991 <br />RE: Updated Culvert Inventory TR-50 Trapper Mine C-81-010 <br />(Adequacy response 1/24/91) <br />Dear David: <br />Mined Land <br />Reclamation Division. <br />This letter is in response to the three (3) questions you've posed in TR-50's adequacy <br />review. <br />1) Revisions of Page 4-173, the last paragraph: <br />The final paragraph on page 4-173 has been revised as per our discussion on 1/30/91. The <br />intent of this paragraph is to allow the temporary establishment of culverts within pit <br />areas (BTCA practice) without prior Division approval. Culverts are established in pit <br />areas to enhance vehicle access; 2) Eliminate potential safety hazards to Trapper <br />personnel and equipment and; 3) To minimize erosional impacts associated with vehicle <br />traffic and other pit activity on spoil areas and their subsequent impact to downstream <br />water quality. Since these culverts would be temporary in nature (sometimes only needed <br />for a single day), are considered the best technology currently available practice to <br />minimize erosion to downstream locations and constructed within active pit areas, it does <br />not seem practical to meet Division notification requirements prior to installation. <br />This issue will be discussed further with Fred Banta during a scheduled joint Colorado <br />Mining Association/CMLRD meeting on 2-14-91 in Denver. I hope this issue can be <br />settled to Trappers benefit considering a requirement for Division notification could lead <br />to unnecessary paperwork for Trapper and the Division, delays in implementation of a <br />good conservation practice and the potential degradation of downstream water quality. <br />2) Locations of culvert PY-1 and DUC-1: <br />These questions were resolved with your site visit on 1/30/91 by reviewing the maps that <br />were submitted. <br />3) Page 4-173,... "10-year 24-hour precipitation... yield no runoff': <br />Trapper has submitted runoff curve numbers (CN) in Section XII of Appendix Q. <br />Trapper developed these tables based on the Soil Conservation Service (pp) Curve <br />Number method. These CN's are based on SCS Hydrological Soil groupings, vegetation <br />types with the associated cover density and land use or treatment combinations. <br />P.0. Box 187 Craig, Colorado 81626 (303) 824-4401 <br />