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Taylor Pit due to the nature of multi -seam mining. Backfilling and rough grading commenced <br />once a steady -state condition was reached in each of the pits. <br />The approved backfilling and grading plan for the Colowyo Mine is found in Volume 1 and <br />Volume 12 (South Taylor) of the PAP. Maps 19 and 19B show the approved post- mining <br />topography, Maps 29 and 29A show the backfilling and grading schedule, and Maps 41 and 41A <br />show the location of the permanent, post- mining drainage channels. The pre- mining and post - <br />mining cross - sections are shown' on Maps 20 and 20B, and the permanent drainage channel <br />profiles are shown on Maps 33 and 33B. Exhibits 2A and 2B of the SL -07 application show <br />cross - sections of the SL -07 areas, including approved post mining topography alongside the <br />constructed topography. <br />Drainage reconstruction <br />The approved drainage reestablishment consisted of the design and construction of permanent <br />postmining drainage channels. The post -mine channels for the East Pit and West Pit areas are <br />shown on Map 41, and post -mine channels for the South Taylor Pit area are shown on Map 41A <br />of the PAP. Post -mine channels are designed and certified to safely convey the peak discharge <br />from the 10 -year, 24 -hour storm event in accordance with Rule 4.05.3. Certified designs for the <br />post -mine channels were approved prior to the bond release application and are provided in Exhibit <br />7 of the PAP. <br />IV. OBSERVATIONS AND FINDINGS <br />The following discussion of observations and findings focuses on the results of backfilling and <br />grading work and drainage reestablishment in the East Pit, West Pit, and South Taylor Pit for the <br />Partial Phase I Bond Release. <br />The evaluation of the bond release application included the bond release inspection, an office <br />review of the permit requirements and regulatory criteria, and review of past inspection reports. <br />The bond release inspection was conducted on May 21, 2013. Several items were reviewed by the <br />Division during the technical evaluation of the bond release application before, during, and after <br />the inspection, including: the post- mining topography, cross - sections of backfilled and graded <br />areas, and as -built drainage profiles. <br />During the Phase I bond release inspection, participants walked through most of the bond release <br />request area to allow for visual assessment of compliance with pertinent requirements. <br />Proposed Decision and Findings of Compliance August 2013 <br />Partial Phase I Bond Release SL -07 Page 5 <br />