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Mr. Wallace Erickson April 28, 1995 Page 3 Seneca will slope the existing eroded portion of the outlet channel. Placement of the riprap will armor the minimum width of the entire channel for protection and slow the outlet velocity prior to entering the stream channel. 3. HRD-A1 The erosion in this ditch has occurred at the very bottom and end of this ditch. All flow then continues through culvert HRC-A1 and into sedimentation pond 006. Seneca will grade the existing erosion channel. The riprap will be installed for approximately the last 125 feet of the ditch. This should prevent any further erosion, and any sediment which flows through the culvert will be deposited into pond 006. 4. G-2 Culvert The outlet of culvert G-2 and associated channel down to the Dry Creek stream channel is already protected with rock riprap. Two inlet channels on the north side of Haul Road G, above the inlet of culvert G-2, appear to be delivering the sediment at the pipe outlet. Both of these channels will have riprap placed in them. One row of silt fence will be installed in the haul road inlet channel. Additional sediment is being delivered by HRD-G1R which runs on the south side of Haul Road G. This channel will also be armored with the same riprap near Topsoil Stockpile RR. The existing silt fence above the outlet end of culvert G-2 will be removed and replaced with a new stretch of silt fence. 5. ME-5 Culvert The outlet at this culvert and the resulting sediment deposition into 006 Gulch was written as a modification to the original NOV. The outlet channel from ME-5 is only 20-25 feet to the stream channel of 006 Gulch. Seneca will remove the existing sediment deposition and remove the silt fence that is currently in place. One problem with the existing plan was the silt fence was on the opposite side of 006 Gulch. Once the sediment has been removed from this area a new portion of silt fence will be installed. At the base of the silt fence rock riprap will be placed to act as a type of check dam and help reinforce the silt fence. The following plan is for the abatement of NOV C-95-006 which is located between the "A" and "B" pits. A gully caused by surface runoff from "B" pit reclaimed areas extends from the south of pit ramp F through some rough graded spoil and continues through undisturbed soil and vegetation to the stream channel of 006 Gulch. Drainage ditches for pit ramp F should have diverted the runoff away from the undisturbed areas and down to sedimentation pond 006. It appears that the berm on the south side of the pit ramp was breached on several occasions causing the formation of the gully which resulted in the NOV. To prevent this from happening again