Fairview Lakes gets improvements for 150 year old dam
A dam in Fairview Canyon that was at the top of the state's list of high-risk dames is getting fixed.
The upgrade of the Fairview Lake Dam will smooth out and stabilize the banks of the earthen structure, control water seepage through the bottom of the dam and create a spillway designed to handle what the state calls the "maximum potential flood," among other improvements.
With engineering, the project is projected to cost $2 million. Ninety percent of the cost will be paid by the Utah Division of Water Resources (DWR) under its dam safety program.
The DWR will provide a 20-year, zero interest loan to the Cottonwood-Gooseberry Irrigation Company, the company providing irrigation water to the Fairview area, for the other 10 percent, about $200,000.
The dam was first built in 1869, and then changed and enlarged over the years, although little to no written history exists telling what was done and when, says Eric Dixon, chief engineer for the project.
The fact that the dam was at the top of the high-risk list does not necessarily mean it was in danger of collapse, says Dixon, who is associated with Franson Civil Engineers of American Fork. The dam is built with heavy clay and is still pretty solid.
The biggest factor in the rating, he says, was the fact that there are quite a few cabins below the structure that would be wiped out_ if the dam collapsed or if water overflowed it.
Another consideration was that the dam sits on what is called the Pleasant Valley Fault. There has never been an earthquake on the fault since Utah' was settled. But scientists say if an earthquake occurred; it would be a powerful one.
The bottom line, Dixon says, is that the dam didn't meet current standards, but the work now underway will bring it up to par.
There have been rumors that the irrigation company was going to dredge the lake and raise the height to the dam.
"None of that is true," Dixon says. "We're just rehabilitating the existing dam."
One of the main noncompliant features of the existing dam was its slope. The walls were too steep and, conceivably, susceptible to landslides. As part of the project, the angle of the slopes is being reduced.
The dam also had what a state engineer de- scribed- as "widespread seepage." A substantial stream of water was flowing right though, the structure and had been for years, Dixon says.
It's impossible to completely do away with leaks through dams. "Water finds its way," Dixon says. But a network of pipes, essentially a drainage system, is, being installed to carry water, through the dam without saturating the, dam material. The system will also enable dam operators to monitor water activity, Dixon says.
Before the project started, water from Fairview Lake traveled through a metal pipe to a transmountain tunnel. The tunnel empties into Cottonwood Creek, the stream that flows down Fairview Canyon into Fairview.
But metal is subject to corrosion. Using a process called "fold and form," PVC material was put inside the metal pipe. Then steam was forced into the pipe at high pressure. That molded the PVC into a lining inside the pipe.
Finally, the rehabilitated dam will have a much bigger spillway. That will ensure that if there are extraordinary stream flows into the reservoir in a given year, the water will "get through the spillway rather than go over the top of the dam," Dixon says.
The dam upgrade is the second major project the Cottonwood-Gooseberry Irrigation Co., which has 570 shareholders, has undertaken in the past couple of years.
The company uses the same tunnel for water transport that would be used if the Narrows Project were built.
Parts of the tunnel were collapsing. So a couple of years ago, the irrigation company did $1.6 million worth of work on the tunnel.
It got some grant funding from the Central Utah Water Conservancy District. But it also borrowed about $1 million for the project. That' loan, also at zero percent interest, is being paid over 25 years.
Compared to other irrigation companies in the north county, Cottonwood-Gooseberry is "infrastructure heavy," says company president Lynn Anderson of Fairview. It is one of the few companies with any water storage..
But the water the company delivers the lifeblood for numerous families from Mountainville to Milburn.
While the company provides secondary irrigation water to homes in Fairview City, 80 percent of its water goes- to agriculture. "My largest shareholders are all in agriculture," Anderson says.