_INSPECTION - C1982057 (50) - Laserfiche WebLink

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September 21,2010 C-1982-057/Seneca II-W Mine JRS -Channel PM-413 is a TRM channel in the northeast edge of the south extension area and flows into Pond 015. The channel is a V ditch. The TRM is dislodged from the channel and there is deep gullying from approximately half way from the top of the channel to the bottom of the channel. The gullying is down to the bedrock below the channel. A plan to repair this channel will be necessary. The Division will recommend excluding post-mining channel PM-4D from the bond release. -Channel 006-NE2 is in the north portion of the Seneca II-W Mine and flows into the 006 Gulch channel. A section approximately 600 feet long(0.23 acres in area)in the lower portion of the ditch was excluded from the Partial Phase I Bond Release SL-02. The ditch segment needed additional grading and riprap placement. The ditch is a V ditch with an 8 foot top width, a total depth of 1 foot and a slope of approximately 21%(as compared to a design slope of 24%in this portion of the channel). Seneca has performed the necessary regrading and riprap placement tasks and reseeded the area around the channel. The Division will include this portion of channel 006- NE2 in SL-03. -The 006-Gulch channel is a channel in the north portion of the mine that flows into Pond 006. A section of the channel approximately 600 feet long(0.36 acres)in the portion of the ditch,just above the confluence with channel 006-NE2,was excluded from the Partial Phase I Bond Release SL-02. The ditch segment need additional grading and riprap placement. The ditch is a V ditch with a top width of 6 feet, a total depth of 2 feet and a slope of approximately 5%(as compared to a design slope of 6%in this portion of the channel). Seneca has performed the necessary regrading and riprap placement tasks and reseeded the area around the channel. The Division will include this portion of the 006-Gulch channel in SL-03. Channel Summary -The post-mining channels discussed above have all been constructed as designed with regards to channel bottom width,channel depth and channel lining. There are some variations in some channel locations,channel profiles and channel lengths. These are primarily due to changes in the post mining topography. Channels were field fit to the regraded topography. While the as-built channel profiles measured on the ground matched the information provided in SL-03 Exhibit D,variations were observed from the approved channel profiles provided in Exhibit 20- 5.9 in both channel length and grade. The Division will be releasing all of the post-mining drainage channels,with the exception of post-mining channel PM-4D, in the south expansion area(the SL-03 bond release area)and the channels in the north area that were excluded in the Partial Phase I Bond Release SL-02 as detailed above. Post- mining channel PM-4D will need to be repaired. Once channel PM-4d is stabilized, SCC can reapply for bond release for this channel. -As noted above in the discussion of each individual permanent,post-mining drainage channel,there is some erosion,under-cutting of the TRM and side-cutting in many of the channels. The erosion problems notwithstanding, the channels themselves appear to be relatively stable. All of the flow appeared to be confined to the channels and no flow has jumped out of the channels or blown-out any of the channels. Continual monitoring, maintenance and repair of all of the permanent,post-mining channels will be necessary. The Division will update task 118 in the reclamation cost estimate to reflect the maintenance of these channels. - Surge Ponds—Seneca has built numerous surge ponds in the permanent,post-mining drainage channels at the Seneca II-W Mine to help slow runoff and protect the permanent,post-mining channels and sediment ponds. These surge ponds are permitted as permanent structures that will remain in place to help control runoff from their associated watersheds. A common theme with these surge ponds is that there is some erosion at the inlet side of each of the ponds and erosion at the outfall side of the ponds(the exception being the outfall of the surge pond below the confluence of post-mining channels PM-3/PM-3A at station 13+60,which exhibited little to no erosion). Number of Partial Inspection this Fiscal Year: 3 Number of Complete Inspections this Fiscal Year: 2 Page 9of18