2012-02-01_REVISION - M1979075 - Laserfiche WebLink

Home Browse Search

submitted 4 weeks prior to the expiration of the permit, there is only sufficient time to complete the proposed work presented in this permit. However, plans are provided in this permit application to monitor the impact of the proposed work and provide data for possible future actions in the river. It is important to note that the work proposed in this permit will attempt to stabilize the river bank in the vicinity of the Chamber's pond and attempt to begin the development of a stable single thread channel. We recognize that the point bar opposite of the Chambers pit will continue to migrate northward as material is deposited during high flow periods. Deposition of material in this area will continue to put pressure along the northern river bank. Therefore, future maintenance will be required to keep the main channel open during subsequent runoff events. Recommendations will be made to United Companies to submit a 404 Permit for long term restoration and maintenance activities at the site. Type, composition, and quantity of material to be excavated or placed in the river United Companies proposes to remove river bed material to restore a healthy channel while placing rock and timber to stabilize the river banks. A proposed construction plan is illustrated in the attached Reclamation Plan and discussed below. It is numbered in accordance with the descriptions below. First, a diversion channel (Number 2) would be cut to reroute the river flow while United proceeds with channel reshaping and bank stabilization. This work would also include a temporary coffer dam (Number 1) using material removed from the diversion channel. The diversion channel and dam can be constructed using a dozer. Pebble count data (discussed later in the permit application) indicates that the dominant material in the river is cobble size rocks. Consequently, the amount of fines is minimal, and any disturbances to the stream channel resulting in muddy water flowing downstream will generally dissipate within a reasonable reach of the river. The next phase of the project is to excavate a channel 250 ft. wide, 8.5 to 12 ft. deep, and 1000 feet long. The channel dimensions are based on stream gage data from the U.S. Geological Survey gage stations located near Glenwood Springs and Cameo. Flow at both gage stations is similar due to diversions, but the river is a single channel (C3) at the gage stations, while in the vicinity of the Chamber Pit the river is braided (D3). Preliminary stability analysis following the WARSSS procedure (Rosgen 2006) indicates that Colorado River in the Rifle area is highly unstable with excess sediment. High width to depth ratios indicate the river is unable to adequately transport sediment, thus the braided nature of the river. The City of Rifle is concerned with excess sediment that is impacting the city water intake and the bridge downstream of the site. The design channel for the Chambers pit area is smaller than the channels at the gage stations. Since the river is braided, there are two side channels in the Chambers pit area that transport water. Our goal design is to eventually establish a single channel capable of efficiently transporting the high bedload. Cross - sectional surveys will be taken at several locations in the project area, plus upstream and downstream of the former Chambers Pit. Some cross - sections are provided in this permit and will provide design data plus be monitored on a yearly basis to quantify the impacts of the river restoration project on the river.