2005-03-08_REVISION - M1977205 - Laserfiche WebLink

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North Fork, Gunnison River Ecosystem-Restoration Appendix B: Engineering Appendix Mazch 2005 uncontrolled release of irrigation water across the steep clay slopes adjacent to the river. In addition, some channel incision may be occurring due to the unstable nature of the river channel from in-stream gravel mining upsveam. The site is contiguous with Site 3 on the upstream end. There is approximately 700 linear feet of bank proposed for river restoration along river left. Site Design: The objective at this site is to control irrigation wastewater return to the river, create a riparian buffer between the fields and the river, reduce erosion to the river and slightly realign the channel to reduce shear stress along the meander bend. As the river enters the site from the north it makes a bend to the right along the steep clay bluff. A gravel bar has formed a[ the head of [he meander that diverts flows directly into the bank. Scale 1: The thalweg of the channel would be slightly relocated to create a smooth transition along 1,O501ineaz feet of [he meander. Five j-hooks are proposed along 600 linear feet of the meander to further reduce shear stress and enhance fish habitat. The bank would be cut back to a 3:1 side slope and encapsulated soil lifts installed between the j-hooks with the bottom lift placed at the bankfull water surface elevation. Willow brushmattressing would be installed behind and between the soil lifts. The bank above the willows would be planted with native dryland grasses and shrubs. Cottonwood trees would also be planted across the bank. Irrigation to establish the plants will be accomplished using existing irrigation wastewater and controlled with gated pipe. Excess water will be returned to the river through a drop pipe to prevent erosion. Scale 2: The project limits have also been reduced a[ this site to encompass only the areas directly related to construction. The objective a[ this site is the same and the techniques used to accomplish it are also the same. Upland plantings have been reduced to priority areas and will be implemented in a manner that will encourage natural recruitment. Access and Staging Areas: There is an existing private farm road that enters the site on Waters propeny from J75 Road to the east. Aright-of--way easement will be obtained from the landowner. A level '/. acre site at the end of the access road on Waters property will be used for staging and stockpiles of materials, requiring a temporary easement. Heavy equipment will access the river from a temporary constructed ramp on north end of the site. 6.1.3 Site 3 This site spans both sides of the river including an expansive floodplain on river left. The site is owned by Tom Curry of Tri-County Gravel Company in Hotchkiss. 9,200 linear feet (1 '/, miles) of the river flow through this site which is contiguous to Site 2 to the south and Site 4 to the north. The lower half of [he site is an active gravel mine with two in-stream, permitted mining areas and one off-stream flood lain, permitted azea. The site is located in the N %,, Section 29, SE '/. Section 20, TI4S, R92W, 6 PM and from Latitude 38°48'20",Longitude 107°42'00" to Latitude 38°49' 10" Longitude 107°41'20". NFRIA has been monitoring a permanent cross section approximately'/. of a mile upstream of the north in-stream gravel pit at existing station 274+00. In the fall of 1997 NFRIA documented between 4' to 6' of channel downcutting following the removal of 140,000 cutiic feet of gravel from the north in-sveam pit. In March of ~ ~ -~ ~ ~ ' 2000, NFRIA established and began monitoring six other cross sections throughout [he north pit.. ~ ~ ' - The Vandiford ditch diversion is located behveen the north in-stream pit and the off-stream _ - ~ ~ ~ ' floodplain pit. Bulldozing is performed annually to maintain water levels and associated diversions. B-32