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Page Seven Preliminary Adequacy Review Grand Mesa Coal Co. - Red Canyon Mine Aoril 28, 1981 2.05.3 (9) Underground Development Waste The application expands the waste disposal area indicated in past permits. The expanded refuse pile has an approximate total capacity of 500,000 cu. yds., with an anticipated annual waste production rate of 33,000 cu. yds. The application references two separate geotechnical analyses performed within the mine plan area in the past. These analyses should be included within the permit documents. The application states that a geotechnical investigation conducted by Armstrong Engineers 6 Assoc., Inc., in May of 1980, was used as a reference in determining the stability of the proposed fill and of its final slopes. However, the critical section analyzed by Armstrong 6 Associates, Znc., was significantly different from those depicted in drawings 2.05.3(9)-2 through 6. The older fill was deposited in an existing strip pit whereas the enlarged proposed fill will occupy a sloped foundational area. The applicant should analyze the critical worst case slope section of the enlarged proposed fill using a sophisticated mathematical technique, such as the modified Bishop's method utilized by Armstrong & Assoc., Inc., in their earlier analysis. Mechanical properties used in the earlier analyses are probably representative, but should be reviewed by the professional preparing the new analysis to ascertain their appropriateness, Zn keeping with the Division's request during past reviews, the applicant will have to install appropriate piezometer/test wells to monitor ground water quality and elevation above, within and below the proposed refuse disposal site. 2.05.9 Reclamation Plan 2.05.4 (2) (a) Reclamation Timetable 1. The application states that reclamation of the waste disposal pile will involve a continuing cycle of overburden and topsoil stripping and replacement. The applicant should provide estimates of the acreage to be disturbed by various phases of the reclamation process during each year of the permit term. This would include projections for acreage from which topsoil and overburden has been stripped, area of active disposal, area backfilled, topsoiled, and area reseeded each year. 2. The applicant states that specific dates for the various reclamation activities are dependent upon the rate of fill. However, projections on waste disposal requirements during each year should be made Far enough in advance to allow for topsoil salvage and redistribution to be carried out during the summer and fall. Seeding and mulching operations should be carried out in the late fall, to the extent possible, or in the spring, not "from late fall to early spring" as is stated in the application.