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S?2=.NLECA <br />Coal Company <br />Seneca Coal Company <br />May 3, 2011 <br />Ms. Susan Burgmaier <br />Division of Reclamation, Mining and Safety <br />1313 Sherman Street, Room 215 <br />Denver, CO 80202 p CEIVED <br />RE: Seneca II-W Mine (Permit C-82-057) <br />TR-73 - Pond 016 Area Slide Remediation Plan in G?"i` U' ' `?d?may <br />Mining and Safely <br />Round 1 Adequacy Review <br />Ms. Burgmaier, <br />Seneca Coal Company (SCC) has reviewed your letter of April 5, 2011 and has developed the <br />following responses to the adequacy comments. <br />1. Prior to backfilling Pond 016A, the pond must first be dewatered, and all saturated soils <br />must be removed (NWCC text says "Stabilized", but no details are provided) from pond <br />bottom and in-slopes. <br />Response: As indicated on Exhibits 20-D.2, Pond 016 Area Remediation Plan, a section of the <br />existing Pond 016A embankment will be cut out to allow construction of Channel PM-2. The <br />removal of this section of the embankment will allow controlled dewatering of Pond 016A. <br />Once dewatered, a rock underdrain will be constructed through the center of the pond area (see <br />Exhibit 20-D.2) to further allow drainage of any residual water and to allow drier material to be <br />placed alongside the underdrain and across the entire bottom of the pond at approximately 3' <br />deep. This drier material from excavation of the slide area will be thoroughly mixed with any <br />wetter material to provide stabilization throughout the pond bottom. Once the 3' of mixed drier <br />material is placed the entire area of the fill will be covered with geotextile. <br />Material excavated from the slide area will be backfilled over the geotextile to the approximate <br />proposed level shown on the postmining map. There will be no anticipated source of water for <br />continued infiltration into the fill area. <br />2. Standard Proctor curves must be developed for any materials used backfill Pond 016A. <br />The use of curves developed previously for other SCC projects is not acceptable. <br />Response: NWCC under contract to SCC will provide compaction testing services during <br />construction of fills in Pond 16A. The fill materials will be sampled by NWCC as they are being <br />excavated from the Pond 16 excavation and placed in Pond 16A fill area. The samples will be <br />Seneca Coal Company* P.O. Box 670 • Hayden, Colorado 81639 <br />Telephone (970) 276-5219 a FAX (970) 276-5222