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STATE OF COLORADO <br />DIVISION OF RECLAMATION, MINING AND SAFET <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, Colorado 80203 <br />Phone: (303) 66 -3567 <br />FAX: (303) 832-8106 <br />COLORADO <br />D I V I S ION O F <br />RECLAMATION <br />MINING <br />S AFETY <br />Sill Ritter, Jr. <br />March 18, 2010 Governor <br />Harris D. Sherman <br />Mr. Roy Karo Executive Director <br />Seneca Coal Company LLC Ronald W. attan 670 P. �� Di Director <br />Pr <br />iaturai Resource Trustee <br />Hayden, Co 81639 <br />1E. Seneca Yoa Mine (Permit N. C -1 082) <br />Technical Revision N . 46 JR- <br />P rnd 012 Slide l emedlati n <br />Dear Mr. Isar : <br />The Division has reviewed the referenced technical revision application, whi addresses <br />rernediati n of the Pond 012 slide. The submittal includes a one page summary of proposed <br />remediation (prepared by SCC), along with the report "Supplemental Geote hni al Investigation <br />and Additional Stabilization/Reconstruction Recommendations", prepared by North West <br />Colorado Consultants, Inc. (NWCC, Feb. 2010). Two previous reports prepared by NWCC of <br />the Pond 012 silde were incorporated into the permit with T -38 ( NWCC, Sep. 200 8) and Tl R-42 <br />( NWCC .July 2009). We have a number o f adequacy concerns, set forth below. <br />1. 1,11,1e have questions regarding certain remediatl n plan details in which the slide <br />remedlati n summary page prepared by SCC does not correspond with the details <br />provided in NWCC Feb. 2010 sheets 1 (Plan Vier ) and 2 (Cross Sections) <br />al For revised Channel P11 - -3, the SCC summary does not include the 7' minimum <br />thickness of screened gravel and perforated PVC pipe that is shown on NWCC Sheet <br />Channel Detail. Please clarify the intended placement of screened gravel in the <br />bottom of YPM- - . <br />b The SCC summary indicates a 5 foot depth of gravel within the proposed open <br />de watering trench, whereas NWCC shows I foot minimurn . Please clarify the <br />intended thickness r range o f thickness) of screened gravel in the bottom of the <br />trench. <br />c The SCC summary page lists the slide scarp cut slope at 1 .5KIV, while NWCC's text <br />and Sheet 2 indicate 0. H :1V for competent bedrock (arid 2H: IV or flatter for weathered <br />materials). Please explain the discrepancy, clarify the planned slope of the scarp <br />cut slope, and modify the tent, plan prier, and cross sections a <br />2. The proposal indicates that the slide scarp would be cut back into competent material, <br />with a very steep out slope {disparity between NWCC and SCC proposed slope will reed <br />Office of o ffice of <br />Mined Land Reclamation Denver 9 Grand junction • Durango Active and Inactive Mines <br />