_GENERAL DOCUMENTS - C1981017 (262)

Home Browse Search

Mr. Jim Herron, MLRD January 30, 1984 Page 2 The entries will be timbered on each side of the concrete wall to prevent excessive loads from bearing upon the concrete wall. The entries and portal tunnels will be backfilled with dirt from the wall out to the surface. Drain pipes comprised of 4-inch diameter Schedule 40 PVC pipe will be installed through the concrete wall and backfilled to allow drainage through the seal. The design is based on a U. S. Environmental Protection Agency publication entitled Inactive & Abandoned Underground Mines, Water Pollution Prevention and Control. As mentioned above, the first few courses of liner plate and steel ribs and the concrete portal structures will be removed and the surface recontoured. TOXIC DISCHARGE In the event that the mine water is toxic and nondischargeable quality, pennanent mine seals will be constructed. Permanent seal design basis, hydrau- lic heads and seal locations are discussed in this section. SEAL LOCATIONS Four sets of seals will be constructed in the rock tunnels after abandon- ment of mining operations. The seals will be located so as to maintain the major aquifer paths, and prevent mixing of water between the aquifers in the rock tunnels. The seals will be at: (1) the rock tunnel portals, (2) the Cozzette Sandstone, (3) the Rollins Sandstone, and (4) the Middle Sandstone members. Locations are shown on Drawing Table 1 Seal No. Head (ft) psi psf 1 1525 661 95,225 2 1157 502 72,246 3 688 298 42,960 4 866 376 54,075 Table 2 Design Force(lbs) Seal No. Tunnel Force (lbs)x102 w o S.F. x106 w/S.F.= 3 lA North 15,712.5 16 48 1B South 18,093.2 18 54* 2A North 11,920.6 12 36 2B South 13,726.7 14 42 3A North 7,088.4 7 21 3B South 8,162.4 8 24 4A North 8,922.4 9 27 4B South 10,274.3 10 30 *Design force for all seals = 54,000 kips