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October 1, 2014C-1992-080/Carbon Junction MineMLT <br />In the uppermost segment of the diversion channel, where the grade is flatter(1%to 2%), the <br />riprap was largely buried and the channel filled by afreshdepositofsediment (Photo 4). <br />In November 2013, an extension to the riprap’s left (south) bank was constructed to ensure <br />that flow from the Upper Carbon Junction Channel is successfully diverted into the <br />Permanent Diversionand not allowed to bypass the lined channel. This riprap extension was <br />found to be in good condition, and appeared to have functioned as designed (Photo 5). <br />Upper Carbon Junction Channel <br />The channel upstream of the permanent diversion was reconstructedin November 2013, as <br />noted in previous inspection reports. In addition toregrading approximately 1,000lineal feet <br />of the Carbon Junction channel, theproject (Permit Appendix 5-12,Maps C1.3 andC2.0) <br />includedriprap lining ofthe unnamed tributary that approaches the Upper Carbon Junction <br />Channel from the south. <br />From Station24+to 28+(Map C1.3), just upstream of the permanent diversion, the channel <br />profile is between 3 and 4 percent. Recent flow through this reach had been wide, and both <br />sediment depositionand erosion had occurred(Photo 6). Overall, this portion of the channel <br />was in good condition. <br />For the next ~700 feet, the channel gradient steepens;in this reach,the flow path was slightly <br />incised,andthere was noticeably lesssediment deposition.It was evident that the water had <br />been moving at a higher velocityhere(Photo 7). <br />Some downcutting had occurred near Station 36+,where the former temporary diversion <br />berm oncetied into the hillside.This erosion was not surprising, given both the apparent <br />volume and speed of water that had passed through the channel,and the steepness of this <br />section. Boulders and cobbles placed here in 2013 for protection of the channel had been <br />washed a distance downstream. The new morphology of this spot (V-shaped channel, <br />exposing sandstoneand shale bedrock, Photo 8)is virtually identical what exists in the native <br />channel justupstream of the mine’s disturbed area (Photo 11). <br />Below the reclaimed North Pit slope, the channel functioned well, with no problems <br />observed. There continues to exist a narrow,defined channel representing the Ordinary High <br />Water level, with elevated flatter zones on either side to accommodatelarger flow events <br />(Photo 9). <br />At the upstream end of the permit area, I observed evidence that flow emanating from the <br />native channel had entered the permit area with force.A small cottonwood was knocked <br />down, and the debris which was trapped againstthe treeincluded cobble-sized rocks (Photo <br />10). <br />Unnamed Tributary <br />This riprapped channel performed relatively well, although boulders which comprised the <br />downstream toe of the channel were dislodged by theflow in the main Carbon Junction <br />channel (Photo 11). <br />Rocks comprising the channel were shifted around to some degree(Photo 12),similar to <br />what was observed in the Carbon Junction Permanent Diversion(Photo 3). <br />Number of PartialInspection this Fiscal Year: 2 <br />311 <br />Number of CompleteInspections this Fiscal Year: 1Page of <br />