2016-01-07_GENERAL DOCUMENTS - C1981019

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3. Hillslope design/function with regard to erosion; 4. Swales and depressions with regard to numbers of features and effect on post-mining land use; 5. Blending of regraded land to undisturbed areas; 6. The functioning of drainages with regard to knickpoints, blending at disturbance boundaries and channel erosion; 7. Erosional features; and 8. Drainage control for the reclaimed area, including upslope diversions. Colowyo’s approved reclamation plan was prepared in accordance with Rule 2.05.4. Colowyo was granted a variance for contemporaneous reclamation for the East Pit, West Pit and the South Taylor Pit due to the nature of multi-seam mining. Backfilling and rough grading commenced once a steady-state condition was reached in each of the pits. The approved backfilling and grading plan for the Colowyo Mine is found in Volume 1 (East and West Pit) and Volume 12 (South Taylor) of the PAP. Maps 19 and 19B show the approved post- mining topography, Maps 29 and 29A show the backfilling and grading schedule, and Maps 41 and 41A show the location of the permanent, post-mining drainage channels. The pre-mining and post-mining cross-sections are shown` on Maps 20 and 20B, and the permanent drainage channel profiles are shown on Maps 33 and 33B. Exhibits 2A, 2B and 3 of the SL-08 application show cross-sections of the SL-08 areas, including approved post mining topography alongside the constructed topography. Drainage reconstruction The approved drainage reestablishment consisted of the design and construction of permanent post-mining drainage channels. The post-mine channels for the East Pit and West Pit areas are shown on Map 41, and post-mine channels for the South Taylor Pit area are shown on Map 41A of the PAP. Post-mine channels are designed and certified to safely convey the peak discharge from the 10-year, 24-hour storm event in accordance with Rule 4.05.3. Certified designs for the post-mine channels were approved prior to the bond release application and are provided in Exhibit 7 of the PAP. IV. OBSERVATIONS AND FINDINGS The following discussion of observations and findings focuses on the results of backfilling and grading work and drainage reestablishment in the East Pit, West Pit, and South Taylor Pit for the partial Phase I Bond Release. The evaluation of the bond release application included the bond release inspection, an office review of the permit requirements and regulatory criteria, and review of past inspection reports. The bond release inspection was conducted on 22 September 2015. Several items were reviewed by the Division during the technical evaluation of the bond release application before, during, Proposed Decision and Findings of Compliance January 2016 Partial Phase I Bond Release SL-08 Page 5