REP00737 - Laserfiche WebLink

Home Browse Search

I ~ 2 The recommendations contained in CTL Thompson's May 5, 1995 report to Colowyo could be incorporated into this revision. The remedial measures should ideally be approved in the permit prior to implementation. However removal of the topsoil stockpile and excavation of the spring sources should proceed as soon as ground conditions allow. The movement expressed on the slope next to the West Pit excess spoil fill has now extended to the edge of, and possibly into, the fill. The stability of the fill is not being incorporated into NOV C-90.005. However, we are concerned that the assumptions used in the stability analysis of the fill and the monitoring plans for verifying the fill's stability may not be appropriate under present circumstances. We are not aware that the water source next to the toe of the fill or the water presently impounded in the pit were anticipated when the CTL Thompson design work was performed. In order to verify the stability of the excess spoil £II, we will also require that Colowyo, 1. visually monitor the face of the fill for any evidence of instability on a weekly basis, at least until topsoil is spread over the fill, 2. submit an appropriate analysis and account of the infiltration of water presently impounded in the West Pit, specifically addressing whether the water may be infiltrating into the excess spoil fill, 3. install the piezometer included in the fill construction plans as soon ground conditions allow. If water is encountered in the fill, a second piezometer on an upper bench of the fill should be installed so the phreatic surface within the fill can be estimated. 4. explain how and if the recommendations to line pit benches and seal coal seams on the north end of the pit are being implemented. These recommendations are found on page 13 of the CTL Thompson report in Exhibit 19, Section I.c of the permit application package.