_INSPECTION - C1982057 (50) - Laserfiche WebLink

Home Browse Search

September 21,2010 C-1982-057/Seneca II-W Mine JRS only minor erosional issues observed in the channel. There are two surge ponds in channel PM-2B. One surge pond is at station 8+06 and the other is at station 10+79(on the Division's channel profile). There was some erosion at the inlets and outfalls of each of the two surge ponds. The as-built channel profile for channel PM-2B is between 25 and 60 lower than the design profile due to changes in the post-mining topography and channel location. Based on the changes, the as-built channel is slightly steeper at station 10+79 and again from station 16+40 to station 21+49. The channel was stable overall and no problems were noted from the slightly steeper grade around station 10+79. The channel and associated surge ponds appeared to be functioning as designed. -Channel PM-2C was not walked during the inspection. Based on a comparison of the as-built channel and the designed channel it appears the as-built channel is much shorter and deviates from the designed channel. As stated in the discussion of channel PM-2B above,channel PM-2C intercepts channel PM-2B approximately 250 feet farther east than the design shows. There is also an unnamed channel to the north of channel PM-2C that does not have an approved permanent,post-mining channel design. The channel appeared to be well vegetated and stable and there did not appear to be any erosional problems related with channel PM-2C. The channel appeared to be functioning as designed. -Channel PM-2D runs from south to north and flows into the Upper end of channel PM-2B. The as-built channel location deviates from the designed location below stock tank T-26 and generally follows the designed location above the stock tank. There was some side-cutting on the east side of the channel below stock tank T-26 but the majority of the channel itself was stable and showed little erosion. The exception to this was the lower approximately 50 feet of the channel,where it intercepts channel PM-2B,where there was down-cutting in the channel of approximately five feet. The channel flows through a 24 inch culvert(under a remaining road)at approximately station 11+27. The culvert was clear at the time of the inspection. There were no erosional problems noted at the outfall of stock tank T-26. It is difficult to compare the as-built channel profile to the designed channel profile because of the significant changes made to this channel and channel PM-2B. The majority of channel PM-2D appeared to be stable at the time of the inspection. The down-cutting in the lower 50 feet of the channel, at the intercept point with channel PM-2B,will need to be repaired. This is a maintenance task that is accounted for in the reclamation cost estimate. The channel appeared to be functioning as designed. -Channel PM-2E runs from southeast to northwest and intercepts channel PM-2D at approximately station 11+27. The as-built channel location is approximately 25 feet west of the design location,primarily due to the change in location of channel PM-2D. The as-built channel PM-2E generally follows the designed flow path. The channel had a fair amount of vegetation growing in the riprap and there were no visible signs of erosion. The as-built channel profile is less than four feet lower than the designed channel profile and maintains an identical grade. Overall channel PM-2E appeared to be stable and functioning as designed. -Channel PM-3 runs along the north side of the Seneca II-W South area and flows from northeast to southwest. It flows into channel PM-2 and ultimately into Pond 016A. The as-built channel location was basically the same as the designed channel location but the as-built channel does not meander as much in the middle portion and it does not go up the regraded slope as high as the designed channel. The channel itself was stable with very little erosion,although there was some rilling going into the channel and areas on the north side of the channel with minor side-cutting. There was also some under-cutting of the TRM in places. There is a surge pond at approximately station 13+60, on the Division's profile,where channel PM-3A intercepts channel PM-3. There was some erosion and down cutting at the inlet of the surge pond while the outfall of the surge pond exhibited little to no erosion. Although the as-built channel does not meander as much in the middle section as the designed channel,the as-built channel profile is basically identical to the designed channel profile. Channel PM-3 appeared to be stable and functioning as designed. -Channel PM-3A runs along the north side of the Seneca II-W South area and flows basically from east to west. The channel intercepts channel PM-3 at approximately station 13+60 at a surge pond. The as-built channel Number of Partial Inspection this Fiscal Year: 3 Number of Complete Inspections this Fiscal Year: 2 Page 7 of 18