The 2024 Yonts Water Conference, on April 10, hosted representatives from the Goshen Irrigation District and HDR Engineering, who presented an update on the progress of replacing the tunnels on the Goshen and Gering-Fort Laramie Irrigation Districts 129-mile-long mainline canal.
“We’ve selected a contractor, Atkinson Construction, a relatively large full-service construction company that has a focused underground division specifically focused on constructing tunnels in North America. So I think that’s a step in the right direction,” said Corey Foreman, HDR Engineering associate vice president.
HDR and the irrigation districts received many bids. The decision was made to go with Atkinson as they did value engineering. When interviewed in August, they asked questions on designs to reduce cost such as the possible saving of the roof on the tunnel. Atkinson will also do construction sequencing, where the construction will work in sequences, doing the floor first and then each side to move through sections of the tunnel quicker and save costs. It is also a safer method, so there are never people underneath any unsupported materials. The sequential excavation of the old tunnel will be replaced with a new and larger reinforced concrete structure every four feet or so. The tunnel design will be like the old tunnel with increased flow capacity.
“That’s ultimately what we’re working on today. I’m working with the contractors, and we’re working on a lot of the proposed construction sequencing,” said Foreman.
The failure of Tunnel No. 2 on July 17, 2019, caused a geotechnical risk with hourglass sands, which could lead to increased cost assessment. Atkinson will be on site Monday, April 15, setting up equipment to pull cores from the concrete and behind it. The company has a three-week window to pull cores before they have to pull out and the tunnels fill with water for irrigation. Foreman said they are hopeful this will give them a better idea of cost estimates.
“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 good value to lower that cost,” he said. In May 2023, the cost of both tunnels was $74 million, an inflated mid-point of construction could see the costs rise to $84 million.
Foreman said the timeline for starting and completing both tunnels is in flux. Pending all agencies’ approval, the new tunnels’ replacement or construction may occur in the fall of 2024. 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.
Further site investigations, NEPA permitting and documentation and rights-of-way considerations must be completed.
Complete background and history of the tunnel collapse and canal breach can be found at UNL CropWatch under Canal Irrigation https://cropwatch.unl.edu/tags/canal-irrigation .
