2010-10-21_REVISION - C1982057 - Laserfiche WebLink

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The approved channel designs, profiles and SEDCAD modeling are based on the locations shown on Exhibit 20-2, which was engineer certified on 28 August 2007 with TR-59. Their as-built channel locations, as shown on current Exhibit 20-2, which was engineer certified on 12 May 2010 with TR-68, are, in most cases, different than those shown on the previous version of Exhibit 20-2. Seneca will need to provide a technical revision to the permit updating the channel locations, profiles, designs and SEDCAD modeling to match what has been constructed and currently exists on the ground at the Seneca II-W Mine. This revision will need to be evaluated and approved prior to the Division's approval of SL-03. - As noted above in the discussion of each individual permanent, post-mining drainage channel, there is 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. Seneca will need to continue to closely monitor and repair all of their permanent, post-mining channels and repair them as necessary. The Division will be adding a reclamation task to the cost estimate for the maintenance of the permanent, post-mining 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 currently permitted as temporary structures that will be removed at a later date, once their associated watersheds have matured to the point where runoff is more controlled. A common theme with these surge ponds is that there is some erosion at the inlet side of each of the ponds and fairly significant 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). Seneca will need to continue to monitor these surge ponds closely and perform maintenance work as necessary to ensure the ponds and their associated post-mining channels remain stable. The Division will add a reclamation task to the cost estimate to account for maintenance and removal of these surge ponds. The Division would also like to see the location of these surge ponds depicted on the as- built exhibit for the post-mining drainage channels for SL-03 (Exhibit D). Please update SL-03 Exhibit D to show the locations of the surge ponds, as appropriate, in the post- mining channels. - Stock Tanks - Seneca has three stock tanks in the Seneca II-W Mine South area. The stock tanks are T-25, T-26 and T-27. As with the surge ponds discussed above, there was erosion at both the inlet and outfall sides of these stock tanks. Seneca was repairing some of the erosion problems on the stock tanks in the PM-2 drainage area at the time of the inspection (T-26 and T-27). Seneca will need to continue to closely monitor these stock tanks and repair any problems as necessary. The Division will add a reclamation task to the cost estimate to account for the maintenance of the stock tanks at the Seneca II-W Mine. Since these stock tanks are in the permanent, post-mining drainage channels, the Division would like to see their location depicted on the as-built exhibit for the post- mining drainage channels for SL-03 (Exhibit D). Please update SL-03 Exhibit D to show the locations of the stock tanks, as appropriate, in the post-mining channels. The following is a picture log for the pictures I have placed at M:\coal\dtm\s1-03 from jrs: