An engineering study said a 1,700-feet stretch — about a third of a mile — of a canal downstream of the Rattlesnake tunnel is likely to fail. The canal provides irrigation water to more than 30,000 acres and serves 675 individual landowners, …
Report says ‘major failure is likely’ on part of Heart Mountain Canal
A portion of concrete canal lining in the Heart Mountain Irrigation District could fail, and Heart Mountain Irrigation District users must decide whether to OK the repairs.
An engineering study said a 1,700-feet stretch — about a third of a mile — of a canal downstream of the Rattlesnake tunnel is likely to fail. The canal provides irrigation water to more than 30,000 acres and serves 675 individual landowners, according to the study. The existing liner was built in 1938.
The state of Wyoming likely would pay two-thirds of the cost of repairs through grant funding, but the district would nonetheless need to cough up hundreds of thousands of dollars and possibly more.
District users will decide Thursday whether to increase their water assessment to pay for the repairs.
The study showed it wasn’t a matter of if the liner would fail, but when, said a letter from Randy Watts, Heart Mountain Irrigation District manager to district water users.
“In order to pay for our portion of the project, we will need to raise per-acre cost from $1 to $3, depending on the repayment schedule we choose,” Watts wrote.
The Wyoming Water Development Commission held a public hearing on Wednesday in Cody to receive comments on the Heart Mountain Canal Rehabilitation Level II Study.
Ten people, including district users and board members, attended the hearing.
The district requested the study to assess recent concrete liner failures, determine the cause and provide recommendations for canal rehabilitation or replacement, according to a commission handout. The commission contracted Engineering Associates of Cody and Powell in 2015 to complete the study.
Visual inspections revealed deteriorating concrete, exposed rebar and excessive cracking on 182 panels. Twenty-nine sections of the liner wall and floor had suspected hollow areas, according to the study.
“With the amount of cracking, poor subgrade (and) age of existing liner, another major failure is likely,” Engineering Associates concluded. “Trying to ‘Band-Aid’ fix the existing liner will only postpone the inevitable replacement.”
If the canal fails where repairs are needed, none of the users would receive water, Watts said.
The study listed 12 repair options, with two preferred recommendations. Estimated costs of the options ranged from more than $800,000 to more than $7.7 million.
If sufficient funding is available, rebuilding should be completed using seven 9-foot by 18-foot box culverts, according to the study. That would be the most prudent, providing the longest life span and minimal maintenance. The cost estimate for that option was more than $7.7 million.
If funding is a concern, the concrete liner could be replaced at an estimated cost of more than $2 million.
“I’d say 99 percent of the users would say go with (replacing) the liner,” said Brian Duyck, district president.
Dave Myer, commission project manager, reminded attendees that the proposed options were estimated costs.
The district must submit an application for the liner, culvert or other repairs to the Wyoming Water Development Commission by Oct. 1. At the commission’s November meeting in Casper, the commission would decide whether to recommend funding the district to the Wyoming Legislature, Myer said. The Legislature would determine whether to allocate funding when it convenes in January 2017.
If funding is approved, the commission would provide 67 percent of the cost, leaving the district to furnish the remaining 33 percent.
The district could cover its share with employee labor, Watts said. The project could not be done in one fall/winter, when the district undertakes projects, but would be completed over the course of a number of years.
Watts said he could not make the decision to go forward with the application. That is up to the district’s water users, who would pay for the repairs through water assessments.
In July 2011 the canal failed, the Engineering Associates report said. The canal was closed for repairs two days.
“It needs to be done,” said Kelly Spiering, a district user.
The district needs a majority of the users to agree to the project. The meeting will take place at 7 p.m. Thursday at the Mountain View Clubhouse at 1000 Road 18, off Wyo. Highway 294.
The Heart Mountain Canal liner, just downstream of the Rattlesnake tunnel, must be repaired, according to the district’s manager and an engineering study.
Late Friday afternoon Heart Mountain Irrigation District Manager Randy Watts maneuvered his pickup truck over County Road 2ABW. The track can be accessed off Wyo. Highway 120 on the north side of the Belfry Bridge, outside Cody.
This is the most direct route to the liner where it exits the tunnel below Rattlesnake Mountain, Watts said.
It’s a rough road that would require upgrades to allow heavy equipment and concrete batch trucks to negotiate it, Watts said. Fuel, employee windshield time and onsite repairs to equipment would have to be factored into the cost.
Watts was examining the canal where an Engineering Associates study says repairs must be made. Repair or liner rehabilitation costs are estimated to be in the $2 to $7.7 million range, depending on the type of repairs.
It’s a rough, yet lovely landscape. The green water sprinted from the tunnel to sparkle like stained glass in the afternoon sun. Hills sprouting huge chunks of limestone advance from the base of the mountain amid grass, sagebrush and scraggly juniper. Further downstream, insects scooted on the canal’s placid surface, which would look mighty tempting to trout. Around bends, ducks winged off the canal as Watts drove by.
The tunnel and canal were completed in 1938, Watts said. “That’s past the expected lifespan when they installed them.”
Water has leached into the limestone below the liner to subsurface caverns, Watts said.
The canal was running 910 cubic feet per second in July 2011 when it failed, Watts said. Three hundred fifty cfs were lost. It simply disappeared into the spacious hollows below.
It took 3 1/2 days to repair the breach, with hundreds of yards of grout pumped into the caverns. Meanwhile, “The farmers said they were watching their crops die,” Watts said.
When running the canal at full capacity, the water reaches the freeboard (waterline) only an inch or two below the top. The old concrete liner resembles exposed aggregate — pebbles embedded loosely in their cement bond.
When the repairs are made, the liner must be higher to handle capacity flow, Watts said.
The irrigation district can apply for a 67 percent grant from the Wyoming Water Development Commission.
Once the application with the commission is filed, and if it is approved by the commission and Legislature, canal rehab could begin in the fall/winter of 2017-18, Watts said. Repairs would likely take up to five winters when the canal is off.
Commission funding will be set at a specific amount. The grant would be for materials only, such as concrete, rebar and gravel. Any additional costs will be up to the district to provide or find, Watts said.
“We’re going to have to do it, no matter what,” he said.
The canal may be aging, but there are countless harvests under its bridge, so to speak.
“Over the 80 years there’s been 80 years of crops,” Watts said. “It worked.”