Construction is under way on the $27 million Elkhead Reservoir enlargement project.
The project, 15 years in the making, almost will double the size of the reservoir that sits on the border of Moffat and Routt counties.
Dan Birch, Colorado River Water Conservation District project development man-ager, said the project should be complete and the reservoir should be open to the public in spring 2007.
The reservoir is closed during construction.
Elkhead was built in 1974 as a 13,700 acre-foot reservoir. The original dam stood 80 feet tall.
When the project is complete, the reservoir will hold about 25,000 acre-feet of water. The new dam will be 105 feet tall.
The reservoir was drawn to about half of its regular size to allow construction to start.
Conservation District spokesman Chris Treese said the reservoir wasn't drained all the way to save the fish that live there.
"Draining it all the way would have been easier (for construction)," Treese said Thursday as he walked near the dam.
Screens were placed on the spillway to stop fish from escaping during draining, but the screens failed, and some fish escaped.
"That was something we were very sorry to have happen," Birch said.
The project also had some problems during excavation.
The shale on which crews hoped to build the spillway crumbles when it's exposed to air, so a thin layer of concrete had to be laid on top of it before the spillway can be built.
"When you excavate, you don't always know what you're going to encounter," Birch said.
In addition to the new spillway, the reservoir also will have new outlet works under the dam.
The outlet works will allow officials to control flows into Elkhead Creek, which flows into the Yampa River.
Augmented flows will maintain water levels in the Yampa needed to sustain endangered fish species. The Yampa doesn't have a dam on it, making it prone to low flows during drought years.
Birch said the Elkhead Reservoir expansion will allow the Upper Colorado River En--dangered Fish Recovery Program to keep the river at the level endangered fish need to survive.
"The real motivating force behind the project was to recover the endangered fish species," Birch said Thursday afternoon as he watched construction crews excavate the earth where the reservoir's new spillway will sit.
The recovery program has a lease on 7,000 acre-feet of the reservoir for the next 20 years. It can use the water to raise the level of the Yampa whenever it is necessary.
"It's not a huge amount of water but enough to provide basic protection for the fish," Birch said.
Recovery program director Bob Muth said officials probably will increase water flows during spring runoffs.
"That's when all the important habitat work gets done," Muth said.
Heavier runoff flows clear out debris from spawning areas.
The conservation district also can use 6,750 acre-feet of water for human use.
The enlargement project is a partnership of the conservation district, the city of Craig, the Craig Station Power Plant, the recovery program and Colorado State Parks.
Spokesman Treese said the project is unique because of the partnership.
Reservoir projects in Oregon and Tennessee have run into problems because they didn't protect endangered species.
"The federal government came in and shut down water users," Treese said.
Because the Elkhead Res-ervoir is intended to help recover endangered species, Treese and Birch said the Endangered Species Act will not become a hindrance, as it did in other places.
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