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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 are shown <br />on Permit Map 41. Post -mine channels are designed and certified to safely convey the peak <br />discharge from the 10 -year, 24 -hour storm event in accordance with Rule 4.05.3. Certified designs <br />for the post -mine channels were approved prior to the bond release application and are provided in <br />Exhibit 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 and West Pit for the Partial Phase I Bond <br />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 August 8, 2012. Several items were reviewed by <br />the Division during the technical evaluation of the bond release application before, during, and <br />after the inspection, including: the post- mining topography, cross - sections of backfilled and <br />graded 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. The data <br />used to confirm the post- mining topography and permanent, post- mining drainage channels was <br />collected with a handheld GPS device (Trimble RTK) and Trimble Terrasync software. The data <br />was analyzed with the following software: Trimble Pathfinder Office, ESRI ArcMap, and <br />Microsoft Excel. A summary of the observations are discussed below, and the details are further <br />discussed in the inspection report. <br />Backfilling & Grading <br />Observations were made during the bond release inspection with regard to approximate original <br />contour and stability of the reclaimed landscape. <br />The maps included in the inspection report show the locations of the data points, which fall into <br />four categories: <br />• Data points on cross sections from the SL -06 application (see Exhibits in application) <br />• Data points along drainages <br />Proposed Decision and Findings of Compliance April 2013 <br />Partial Phase I Bond Release SL -06 Pages <br />