7738 ‎(2)‎

• UCREFRP Catalog Number: 7738
• Author: Ruppert, J. B., R. T. Muth and T. P. Nesler
• Title: Predation on Fish Larvae by Adult Red Shiner, Yampa and Green Rivers, Colorado
• USFW Year: 1993
• USFW - Doc Type: The Southwestern Naturalist
• Copyright Material: NO

Executive Summary

1

in the right abutment to an adjacent drainageway which joins Elkhead Creek one mile
downstream.
The Elkhead Dam raise would be accomplished on the downstream slope of the existing
dam. The upstream riprap slope would be extended to the new crest elevation at its current 3:1
slope. Following preparation of the downstream slope, abutment and foundation, a 3:1
downstream slope would be constructed. This would provide greater slope stability than the
existing 2.5:1 slope.
The recommended long-term project considers the enlargement of the existing
Stagecoach Dam and Reservoir. The recommended long-term project calls for the crest of the
dam to be raised 21.5 feet to elevation 7,231.5 feet by addition of roller-compacted concrete to
the downstream face. This elevation was judged to be the maximum reasonable height based
on topography, rock quality and preservation of existing dam features to the maximum extent
possible. The existing 800 kW (kilowatt) powerplant would be unchanged by the enlargement.
Based on more detailed facilities plans and quantity takeoffs and on updated unit costs,
the total development cost (including land and relocation and environmental mitigation) of the
Elkhead Enlargement was estimated to be $29.9 million. Construction costs alone were
estimated to be $19.5 million.
Operating Procedures
General
For purposes of this Study it was assumed that existing reservoirs would continue to be
operated much as they have in the past. The primary exception would be the use of water in
enlargement pools at Elkhead and/or Stagecoach reservoirs. This study also assumed that
efforts will be made to establish and maintain fisheries in and downstream of the enlarged
reservoirs and that the enlarged reservoirs would be operated to maximize recreational usage
and minimize environmental impacts within the limits of water delivery requirements.
A primary function of the enlargement at Elkhead Reservoir would be to make
augmentation water releases to those juniors who would otherwise benefit from the
subordination of the Juniper-based instream flow right at Juniper Canyon. These junior
demands include those that would be served directly by releases out of Elkhead and those that
would be served through exchange. Municipal and industrial (M&I) demands at Craig were
assumed to have access to 1,668 of of existing storage dedicated to M&I use as well as to the
enlargement. M&I demands at Hayden and Steamboat were assumed to have access to contract
storage in Stagecoach Reservoir but also to benefit from the Elkhead Reservoir enlargement
through exchange. All thermal-electric power demands could be served, either indirectly or
through exchange, by the Elkhead Reservoir enlargement pool after utilizing their existing
contract storage supplies. Future Craig area agricultural demands and the proposed coal
gasification plant near Craig were assumed not to have access to existing reservoir storage
water but would be served from storage in the enlargement pool at Elkhead Reservoir.
Reservoir operations in the long-term scenario were assumed to be identical to the near-
term. Water deliveries made out of the enlargement at Stagecoach would be similar to those
made from the Elkhead enlargement. All basin demands could be served by this water on a
first-come, first served basis.
Recreation pools were defined for both the Elkhead and Stagecoach enlargements. The
Elkhead Reservoir recreation pool was defined by a maximum drawdown of 10 feet during the
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