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J. E. STOVER 8 ASSOCIATES <br />2768 COMPASS DRIVE, SUITE 101 <br />GRAND JUNCTION, COLORADO 81506 <br />PHONE: (970) 245-4101, FAX 242-7908 <br />MINE ENGINEERING <br />MINE RECLAMATION <br />December 15, 1998 <br />=1VED <br />J. J. Dudash <br />Division of Minerals & Geology +^^ <br />1313 Sherman St., Room 215 ~ ~ ~ u~8 <br />Denver, CO 80203 & Gea109y <br />Re: Technical Revision No. 28, Post Mine Topography, Bowie No. 1 Mine, <br />Permit No. C-81-038, Bowie Resources Limited. <br />Dear Mr. Dudash: <br />iii iiiiiiiiniiiiii <br />sss <br />CIVIL ENGINEERING <br />CONST. MANAGEMENT <br />BRL has reviewed the hydrology designs for the ditch referred to in the Division's adequacy letter <br />dated December 4, 1998. <br />The ditch segment in question was realigned from Geo-Hydro Consulting's design due to the <br />change in the reclaimed topography derived from the actions taken in the review process for TR- <br />28. The Geo-Hydro design presented in the permit is a general design which specifies 8-inch rip- <br />rap for ditch segments that exceed 5% slope. <br />The amount of runoff the new alignment will realize is less than designed for before due to a small <br />reduction in drainage area. BRL, in order to be conservative, assumed this ditch will need to <br />handle the original flow value of 8.0 cfs. The ditch size and rip-rap size specified on Map 6A-SD <br />Section B-B' was evaluated using the computer program Flowmaster. With the bottom width of <br />5.0 feet, side slopes of 2H:1 V, Manning's n of 0.040, maximum channel slope of 33% and a flow <br />depth of 0.21 feet, this ditch will handle the 8.0 cfs design flow. The design flow produces a <br />velocity of 7.1 fps that will require 7-inch rip-rap. The 7-inches of rip-rap required is smaller than <br />the 8.0 inches specified in the permit. It is BRL's contention the ditch design and analysis for <br />drainage way 2 at node C, in Volume 6A and shown on Map 6A-SD, is adequate to facilitate the <br />realigned ditch segment and the design and analysis does not need to be revised. The general <br />design presented in the permit is applicable to this ditch segment. <br />If you have any questions, please call me. <br />Sincerely, <br />~~~ <br />J. E. Stover, P.E. <br />Consulting Engineer <br />i <br />