Foundation issues slow work on dam
Long Hollow Reservoir project will help Colorado irrigators
The Ute Mountain Ute construction company will be working on a new dam in La Plata County for at least eight months longer than planned after running up against challenges with the foundation. But an unseasonably mild January allowed progress to continue on some aspects when the site would normally be closed.
The new Long Hollow Reservoir dam, which is 5 miles from the Colorado border on Highway 140, will allow water to be delivered to New Mexico more efficiently. It will also help Colorado irrigators access water along the La Plata and help the Ute Mountain Ute Tribe store water when available.
Weeminuche Construction Authority, which is owned by the Ute Mountain Ute tribe, has worked on the project since July 2012 and had been scheduled to finish in December, but the bedrock foundation took months longer than expected to seal with concrete, said Rick Ehat, the construction engineer.
The additional work on foundation set the project back five months, and winter halted work on the embankment at the halfway point December, he said.
Now the new goal for completing the 5,100-acre-foot reservoir is August, said Brice Lee, superintendent for the La Plata Water Conservancy District.
The additional concrete and labor needed to seal the dam required the La Plata Water Conservancy District to seek out additional grants. The Colorado Water Resources and Power Development Authority and the Colorado Water Conservation Board agreed to provide an $3.25 million, said Michael Brod, executive director of the authority.
The Colorado Water Conservation Board is going to seek $1.575 million through the state legislature during the spring session. If appropriated, the funds wouldn’t be available until July. The Colorado Water Resources and Power Development Authority has agreed to cover the cost of the project if the state does not approve the extra funding. Southwestern Water Conservancy District also granted the project an additional $100,000. The project was originally estimated to cost $22.5 million.
The grouting started over the summer, and after workers started pumping concrete into the foundation, the fractures needed far more than planned.
It was originally estimated that 43,000 bags of concrete would seal the bedrock under the dam and prevent water from seeping through, said Aaron Chubbuck, project manager.
During the process, workers drilled holes 2 inches across and many 120 feet deep before pumping them full of concrete grout to fill fractures in the sandstone. The fractures are typical phenomenon in canyons, Ehat said.
A few of the holes took four to five days to fill, said Sam Dils, lead superintendent for the project.
In the end, the bedrock sucked up 134,000 bags of concrete. Ehat doesn’t expect anymore surprises after the foundation.
“We think we have solved all the problems you could have,” he said.
Once the foundation was sealed in July, the team began laying the clay core on the rock foundation. When the project is fully operational Weeminuche employs 60 to 65 people at the site.
The team worked on the dam itself until early December when the weather turned too cold.
All the material for the dam is mined on site, which among other measures helped Weeminuche lower its estimated for the cost of the project at the beginning by about $2 million.
The clay for the dam core was mined from what will become the bottom of the reservoir at the suggestion of Sheldon House, project superintendent.
Originally the plan was to make the core by processing shale on site, but House said he saw the clay as a replacement that didn’t need to be processed and would save the project money.
Once the project is finished, all the massive piles of rock and dirt visible from the highway will be used in the dam or leveled and reseeded.
Mild January weather made it possible for work roads to be improved and smaller projects finished, including lining the new Long Hollow creek channel below the dam with rock.
“We’re able to get these auxiliary items done so we don’t have to worry about them at the end,” Chubbuck said.
When the dam is finished, the conservancy will attempt to fill reservoir the following spring.
Studies based on 30-year averages show the reservoir will only be able to filled completely three years out of 10, Lee said. The plan is to drain it every year to send water to New Mexico.
The Long Hollow dam will store water from Government Draw and Long Hollow Creek about a half-mile from where Long Hollow joins the La Plata.
New Mexico is owed half the water in the La Plata River at Hesperus.
But much of the river water is lost to evaporation, porous soil and plants on it’s 31-mile journey to the border, Lee said.
In recent drought years, all but first-priority Colorado water users have gone without water to help meet the compact.
“Many people haven’t gotten any water for two or three years,” Lee said.