REV105347 - Laserfiche WebLink

Home Browse Search

• Stability analyses for the noted sections indicate a safety factor of 2.4 for cut slopes and a range of 1.7 to 1.8 for fill slopes. Documentation of the stability analyses is provided by a 6/3/97 Lincoln DeVore letter which accompanies these responses for insertion in Appendix L. Oxbow intends to follow the recommendations of Lincoln DeVore for construction of the West Valley Fill and associated haul road based on it's understanding of field conditions. Any significant variance from the assumed field conditions may require modifications from the design criteria during construction. Any such modifications will be developed and implemented with input from Lincoln DeVore and Balaz & Associates, Inc. 18. Lincoln•Devore, Inc., provides a thorough discussion of standard specifications to be used for ~Llechanically Reinforced Earth Fills". However, no indication of the proposed location or implementation of any of these construction methods occurs on the Balaz fi Associate prepared road plan and prof le drawings. The application should specify the location and type of a! stabilization methodology to be implemented Response: Balaz & Associates and Lincoln DeVore have jointly developed design specifications for road construction which are presented and graphically illustrated by Drawing OXWVF-16, Road Section Construction Details (insert in Appendix L). The representative cross-sections illustrated by this drawing provide some flexibility relative to use of the existing materials and adaptation to existing conditions along the road alignment. If actual field conditions vary significantly from those assumed in developing the designs, • modifications from the design criteria may be required during construction. Any such modifications will be developed and implemented with input from the construction contractor, Lincoln DeVore, and Balaz & Associates, Inc. Generally, road fills will be constructed as compacted fills with maximum 1.SH:1V slopes. With realignment of the road az noted in previous Response 17, it is anticipated that requirements for mechanically stabilized fills will be limited to road sections in the immediate vicinity of Station 8+00 and 27+00. 19. Regulations require the Division to consider whether the possible subsidence of previous underground workings within the historic underground of the Somerset Mine might potentially impact the proposed Sanborn Creek Waste Pile. Examination of the latest extent of mining maps for the Somerset Mine and the Sanborn Creek Mine determined that no underground workings existed close enough to the proposed waste pile footprint to potentially impact the pile. However, in order to prevent potential impacts due to future working of the Sanborn Creek Mine, the Division should inform the applicant that no future underground extraction will be approved within any Seam which could potentially subject the pile to subsidence settlement impacts. Response: No future mining of the B or C Coal Seams is planned or anticipated in the area west of Elk Creek since these seams have already been mined. As indicated by the Division, however, no mine workings currently exist in the immediate vicinity of the proposed refuse pile. The potential does exist, however, that known fee and unleazed Federal coal reserves in the D Seam to the west and north of Elk Creek may be developed and mined at some time in the future. Mining in the D Seam and any related subsidence effects would have no effect on the proposed West Valley Fill since the D Seam outcrop is • located at an elevation of approximately 6,350 feet or approximately 100 feet above the top of the West Valley Fill.