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s Colcoma Seneca Coal Company <br />April 6, 2010 <br />Mr. Dan Mathews F(;'?? <br />Division of Reclamation, Mining and Safety <br />101 South 3`d, Suite 301 a `Q?Q <br />Grand Junction, CO 81501PR <br />(970) 243-1571 DIVI?io?? <«`' ' <br />inRng prod <br />RE: Yoast Mine Permit No. C-94-082 <br />Technical Revision No. (TR-46), Pond 012 Slide Remediation Plan (Construction) <br />Response to Adequacy Comments <br />Mr. Mathews, <br />Seneca has reviewed your letter regarding the Pond 012 Slide Remediation, dated March 18, 2010 and as <br />• prepared the following responses: <br />1. We have questions regarding certain remediation plan details in which the slide remediation summary page prepare d by SCC <br />does not correspond with details provided in NWICC Feb. 2010 Sheets1 (Plan View) and Sheet 2 (Cross Sections). <br />a) For revised Channel YPM-6-3, the SCC summary does not include the 7' minimum thickness of screened gravel and <br />perforated PVC pipe that is shown on NWCC Sheet 1 Channel Detail. Please clarify the intended <br />placement of screened gravel in the bottom of YPM-6-3. <br />Response: The placement of the screened -7 feet of gravel and the perforated PVC pipe is SCC's <br />conservative approach at controlling the ground water flow and future ground movement within the channel <br />area. A description has been included in the Summary Sheet. <br />b) The SCC summary indicates a 5 foot depth ofgravel within the pmposed open dewatering trench, whereas NWCC <br />shows 1 foot (minimum). Please clarify the intended thickness (or range of thickness) of screened <br />gravel in the bottom of the trench. <br />Response: It is SCC's belief that the proposed 5 foot gravel depth meets and exceeds the specified <br />"minimum 1 foot" of screened gravel. The placement of the screened -5 feet of gravel is SCC's conservative <br />approach at controlling the ground water flow and future ground movement within the slide area. <br />• <br />Seneca Coal Company a P.O. Box 670 a Hayden, Colorado 81639 <br />Telephone (970) 276-5217 a FAX (970) 276-5222