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Visual inspection of ditch design was also observed at each point to compare with approve channel depth, <br /> channel type,side slopes and channel material(Table 1). Throughout its length,the ditch was observed to <br /> adhere to the given design criteria,with a fully vegetated channel,average total depth of—0.5 feet, and a 2' <br /> bottom channel width. Please refer to the Division's inspection report dated July 22,2025 for photographs of <br /> the ditch design. Visual inspection confirmed that Streeter South Side Ditch blended in well with the <br /> adjacent reclaimed areas.During the inspection,no signs of erosion i s s u e s were encountered,suggesting <br /> that grading and channel establishment has been constructed to encourage proper storm drainage as required. <br /> No areas were identified that would suggest stormwater has flowed or could flow outside of the approved <br /> channel area. <br /> For Streeter South Side Ditch,the Division finds that the Colowyo Mine has achieved a post-mining surface <br /> that conforms to the approved post-mining topography and resembles the general surface configuration of the <br /> land prior to mining.All reclaimed lands blend in well with the adjacent reclaimed slopes. The ditch was <br /> observed to have achieved long term stability and is functioning effectively as a post-mining conveyance <br /> channel. <br /> PHASE II <br /> As per Rule 4.15.1(2)(b),vegetation cover shall be capable of stabilizing the soil surface to achieve erosion control <br /> equal to pre-mining levels.As discussed earlier in this document,there are no topsoil or revegetation requirements <br /> for permanent structures. Rule 3.03.1(3)(b) states that lands to which the release would be applicable are not <br /> contributing suspended solids to streamflow or runoff outside the permit area in excess of pre-mining levels as <br /> determined by baseline data. <br /> To evaluate for compliance with the applicable Rules,the Division refers back to the approval of SL-23,which <br /> Streeter Pond and Streeter Ditch were Phase I,II and III released.Determination of this release included review of <br /> SEDCAD sedimentology demonstrations provided by Colowyo in Exhibit 07 Item 14 Appendix Exh7-14SP as <br /> approved in 2021 under TR-145.Exhibit 07 Item 14 Appendix Exh7-14SP provides demonstrations for a 10-year <br /> 24-hour,25-year 24-hour and 100-year 24-hour storm events for the Streeter Ditch and Pond.The Streeter South <br /> Side Ditch is a channel within the structure networking of this calculation.All calculations demonstrated that <br /> under the design specified,the Streeter Ditch and Pond effectively manage peak flow,runoff volume,and <br /> sediment loads during all required storm test events.This determination was further corroborated by utilizing <br /> design criteria specified in the SEDCAD demonstration for Streeter South Side Ditch in comparison with on the <br /> ground inspected conditions.This comparison revealed that measured design criteria,such as channel width, <br /> depth,and material(Table 1),were consistent with the design criteria provided in the approved SEDCAD <br /> demonstration(Table 2).The Streeter South Side Ditch is constructed and functioning in line with design <br /> requirements and is effectively managing peak stormwater flows,runoff volumes,and sediment loads.This <br /> conclusion is supported by visual inspections of the ditch which showed overall stability in structure design,with <br /> no signs of flow outside the approved channel or erosional features. <br /> PHASE III <br /> Post-mining Land Use <br /> The post-mining land use at the Colowyo mine is rangeland and wildlife habitat. The Phase I,II and III Bond <br /> Release areas requested with the SL-25 application were walked during the inspection. Streeter South Side Ditch <br /> has been retained as a permanent structure in support of the post-mining land use,by providing a water <br /> conveyance structure and water source post-mine.The Streeter South Side Ditch is also heavily utilized by wildlife <br /> as is apparent by the game trails present on the structure.While Colowyo has not used the reclaimed lands for <br /> domestic livestock grazing,there is a large resident elk herd that uses the surroundings reclaimed lands <br /> Proposed Decision and Findings of Compliance <br /> Partial Phase I,II and III Bond Release SL-25 Page 8 of 14 <br />