Representatives from the conservancy districts went to work with the Utah congressional delegation and other agencies in Washington and were able to secure $17.5 million for the trail.
Cain says more than 500 utilities intersect with the canal right-of-way and have to be relocated or replaced in the enclosure project. An agreement between the cities and the PRWUA put the relocation work under the control of general contractor Ames Construction, Salt Lake City.
According to Adam Murdock, engineer-of-record for project designers CH2M HILL (and coincidentally, a great grandson of the canal's namesake), designs for a concrete box culvert were also done, but the final choice was for a pipeline. Murdock says the pipe is more flexible in the event of an earthquake, always a concern along the Wasatch Front, and it provides increased, higher-pressure flow.
“We are welding all the joints on the pipe, and so in the end it will be 100% watertight,” Murdock says.
He points to a unique design feature—the use of new plunger valves to control water pressure in the pipe. “We used them because the elevation drop from the beginning of the pipe to the end is about 90 feet, and to get it to flow that far, we can't have much head loss,” he says. “We have these specifically designed plunger valves that, when open, produce minimal head loss. They should extend the life of the flow-control facilities we are planning to put in operation about a year from now.”
The decision to enclose the canal in a steel pipe had other benefits for the community, Cain says. Northwest Pipe Co., located in nearby Pleasant Grove, was awarded the contract to manufacture all 21 miles of pipe, providing a local economic boost.
The spiral pipe is 7/16 in. thick and produced in 40-ft sections weighing about 23,000 lb each.
The inside of the pipe is coated with polyurethane to prolong its life and allow for a swifter water flow. The original canal managed flows of about 550 cu ft per second, but the new pipe can handle flows up to 623 cfs, Cain says. In the trench, the pipe will rest on a layer of “flowable fill,” a malleable light concrete material pumped in after joints are welded. The flowable material fills the bottom half of the trench, then is topped with sand and soil and will eventually be paved with asphalt for the trail.
Don Brummel, western region construction manager for Ames, says much of the material to cover the pipe has been reclaimed on site. “We are doing the crushing, and we have a batch plant on site,” he says. “We have an outside supplier helping with extra flowable fill, but we are providing the rest of it.”
The contract contains incentives to complete the project in spring 2012, and Brummel says crews are on target for early completion.