Construction on irrigation tunnels may begin this fall

On April 10, University of Nebraska-Lincoln (UNL) Extension hosted the 2024 Yonts Water Conference at the UNL Panhandle Research, Extension and Education Center in Scottsbluff, Neb. 

During the event, representatives from the Goshen Irrigation District and HDR Engineering presented an update on the progress of replacing two tunnels on the Goshen and Gering-Fort Laramie Irrigation districts’ main canal.

The collapse of Tunnel Number Two in July 2019 washed out the supply canal south of Fort Laramie and ended water delivery to local growers for 44 days, affecting nearly 107,000 acres of crops during a critical period of growth. 

In an effort to get growers water the following year, temporary repairs were made by installing steel ribs to support the concrete walls. Then in 2020-21, metal sheeting was installed over the ribs to increase water flow through the tunnels. 

Hiring a contractor 

Recently, the water district hired a contractor – Atkinson Construction – to permanently replace the two tunnels.

Cory Foreman, HDR Engineering associate vice president, told conference attendees they received several bids, but decided on Atkinson Construction because they value engineering and have an underground division focused specifically on the construction of tunnels.

“Atkinson Construction will also do construction sequencing, in which construction will work in sequences, doing the floor first and then each side to move through sections of the tunnel quicker and to save costs,” explained UNL Extension Educator Gary Stone in an April 11 news brief. 

“The sequential excavation of the old tunnel will be replaced with a new and larger reinforced concrete structure every four feet or so,” Stone continued. “The tunnel design will be like the old tunnel with increased flow capacity.” 

Current operations

Foreman explained the three organizations are currently working on this proposed construction sequencing system, and on April 15, set up equipment to pull cores from the concrete as the collapse of Tunnel Number Two caused a “geotechnical risk with hourglass sands.” 

Stone noted the company has a three-week window to pull cores before they have to remove equipment and let the tunnels fill with water for the upcoming irrigation season, and Foreman said they are hopeful these cores will give them a better idea of cost estimates.

As of May 2023,  the estimated cost of both tunnels was set at $74 million, but with rising costs of construction this could rise to $84 million. 

“We want to make sure we evaluate everything, because if there’s a potential $10 million cost savings, we need to do our due diligence wherever we can find a good value to lower the cost,” he said. 

Foreman further noted the timeline for starting and completing both tunnels is up in the air. 

“Pending all agencies’ approval, the new tunnels’ replacement or construction may occur in the fall of 2024,” remarked Stone. “Doing both to finish in one season would mean Atkinson Construction having two back-to-back shifts, which is possible but could be cost-prohibitive. They are also experiencing labor shortages.”

Stone noted further site investigations, National Environment Policy Act permitting and documentation and right-of-way considerations must be completed before the tunnels are replaced.

Hannah Bugas is the managing editor of the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.