7884

• UCREFRP Catalog Number: 7884
• Author: Hydrosphere Resource Consultants.
• Title: Reconnaissance Evaluation of Yampa River Diversion Structures.
• USFW Year: 1995.
• USFW - Doc Type: Boulder, CO.
• Copyright Material: NO

Mitigation and Modification Alternatives
' It is very likely that solutions at individual sites will involve one or more of these
alternatives depending on site specific situations. In addition, a cost-effectiveness evaluation of
potentially feasible options at each diversion of interest will be a necessary element of the
decision making process.
Design alternatives for any modifications should consider depth and velocity criteria used in
the design of the City of Craig structure. Alternative fish passage facilities may be required at
structures with large differences in water surface elevation across the structure. Traditional fish
passage facilities, such as vertical slot, denil, and pool-and-weir-type fish ladders have been
successfully used for non-salmonid passage and should be considered.

Modification Concepts for Problematic Structures
K. Diamond/Patrick Sweeney Ditch
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The distinguishing characteristics of this riprap structure are: 1) the need to serve a
combined function of pumped and gravity diversion of water, 2) its location relative to the bluff
or river right, 3) the flat and broad nature of the river at this location, and 4) the semi-
permanent nature of the instream structure. These and other characteristics of this structure are
summarized in Appendix F. This information was used to configure four possible options for
modifications of this structure.
• No action - leave the structure unchanged.
• Realign the instream diversion into an upstream angling configuration to direct low
flows (and fish) through the normally navigable channel near the pump intakes.
• Reconstruct the diversion upstream (50-300 feet) of its current location, with a
concave cutoff wall and a multi-stage chute-run type fishway in the center, and
relocate pumps to a position upstream of cutoff wall.
• Same as above but convert the means of water diversion to fully pumped scheme.

Fl

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The third of these options was considered reasonably representative of what a future
structure at this site might be and a schematic of this design concept is presented in Figure 4-1.
Rehabilitating the existing structure and changing to a completely gravity delivery configuration
were not considered feasible modification options.
Creating a fish passage route approaching the structure from the downstream direction,
with an adequate, navigable attraction flow, is a key element at this location. Since the plan
location of the structure does not adequately serve this purpose and the structure itself is
structurally inadequate, the construction of a new instream diversion is proposed. The new
diversion will consist of a downstream concave arch-shaped concrete weir which will extend
completely across the river. A second shorter weir, centered on the thalweg, will be located
twenty feet below the first creating a two-stage drop of approximately two feet total. Grouted
rock would contain the low flow. The fishway would be designed to handle up to the mean
annual flood flow at which point the diversion is expected to be submerged by downstream
tailwater.
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