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TerrahAatrix <br />Engitssaring ~ Envitronrtental Services <br />165 S. Unlon BoulevaN • Suite 400 <br />takewo«f. Colorado eozze , ~ r F IV ~~ <br />303-763-5140 •fax 303-763-6003 <br />May 1, 199s ,SAY 031995 <br />l.,J zw,~ ~;. ,.,metals & Geolo9Y <br />Mr. Wally Erickson - <br />Division of Minerals and Geology <br />1313 Sherman Street, Room 215 <br />Denver, CO. 80203 1 <br />I~vn,`rfA' ~S <br />Re: Kerr Coal Company - Marr Mine (Fermi[ No. C-80-006) MR-21 ~ ~ -1/ <br />Dear Wally: % Y~ <br />Accompanying this letter is Kerr Coal Company's (Kerr) application and supporting materials <br />requesting approval of a minor revision (MR-21). The minor revision involves the modification <br />of the ditch designs for permanent diversion ditches PD-1 and PD-2 to reflex the existing ditch <br />configurations and design criteria. Included with this transmittal are three copies of the <br />following: <br />MR-21 Application Form <br />Summary of Revisions and Additions <br />Revised Permit Text and Map <br />Backfilling and regrading aze complete in the 720 Pit area and permanent diversion ditches PD-1 <br />and PD-2 have been established. Using current survey data, Kerr has revised the ditch designs <br />to reflex actual measured grades to confirm that the existing ditches are adequate. To be <br />consistent with current ditch designs, the calculations were condutted using the 10-yeaz, 24hour <br />event. <br />Please feel free to contact me with any questions or if I an provide further clarification or <br />submit additional information that will facilitate your review. <br />Sincerely, <br />TerraMatrix Inc. <br />~..e~ <br />Thomas E. Leidich <br />Project Engineer <br />cc: George Patterson <br />Jackson County Clerk <br />Steamboat Springs, CO • Denver, CO • Seattle, WA • Juneau, AK. Santiago, Chile SA <br />