FORT LARAMIE, Wyo. — Work is progressing meticulously on the repairs to Tunnel 2 of the Gering-Fort Laramie Irrigation Canal, with the focus being on worker safety as crews work two shifts per day on the project.
The July 17 collapse of a 2,200-foot long tunnel caused a canal breach, forcing the Bureau of Reclamation to shut down delivery of irrigation water. The situation has left approximately 108,000 acres of land in Wyoming and Nebraska served by the Goshen and Gering-Fort Laramie Irrigation Districts and the Wright and Murphy Ditch Company without a water source.
Crews are on site from 5 a.m. to 9 p.m. to make maximum use of daylight hours. While Gering-Fort Laramie Irrigation District and Goshen County Irrigation District crews outside the tunnel have been removing dirt from above the collapse and rebuilding the banks of the canal that washed away in the breach, crews from SAK Construction inside the tunnel have been removing debris and working to shore up the concrete interior walls with steel ribbing. Once the outside crews are able to get close enough to the top of the tunnel, they will insert a series of shoring boxes over the top of the tunnel to help alleviate the load placed on the tunnel walls by the dirt and sand on top.
Gering/Fort Laramie Irrigation District General Manager Rick Preston said that it’s difficult to predict when water might begin to flow again.
“Once we can get those shoring boxes in, at the earliest, we might be able to start the water back on (Thursday or Friday),” he said. “If there’s any kind of a hurdle, it could be later. If it’s a big hurdle, it may not happen at all.”
Crews are moving at the quickest possible pace while still maintaining their safety. A 60-inch duct pumps fresh air into the tunnel and monitors check contaminant levels to ensure that the crew is safe inside.
“Right now, the biggest issue is holding the concrete in place while the sand is removed (from the inside),” James Byrd, SAK operations manager-underground division, said.
About 650 feet into the tunnel, Byrd pointed to a cracked portion of the concrete at the top of the tunnel and expressed the difficulty the workers face.
“Part of the problem is knowing that the concrete here is this bad, and not knowing how bad it is as you go further in,” he said.
A retaining wall holds back sand and water until the crews are able to shore up each section of the tunnel. The 14-foot diameter steel ribs are installed every three feet as they’re needed. As each section is completed, the retaining wall moves back and the crews move deeper into the tunnel.
One of the first things that SAK did upon beginning the project is to core out 34 3-inch plug holes. Byrd said the assumption was that there would be voids within the tunnel, so the holes were drilled in order to pump grout into the tunnel to fill those voids as much as possible. The grout enabled the team to even the load and provide support inside the tunnel so that workers could enter safely to start their work.
The steel ribs would normally have taken about a month to produce, but Byrd said his supplier, who was contacted on a weekend and knew the urgency of the project, began production and was able to get 100 of the ribs completed for the project in three days.
Preston said there are three tunnels in the system. Tunnel 2, the one being restructured, is southeast of Fort Laramie, Wyoming, Tunnel 1 is upstream and Tunnel 3 is well downstream in Nebraska. Preston said inspectors from the University of Wyoming have looked at Tunnel 1, but haven’t returned a report on its condition. An engineer will inspect Tunnel 3 to determine if there is any risk in that section as well.
The crews outside the tunnel have been working to restore the structure of the canal wall and bank to the west of the tunnel. They will have to not only do those repairs, but eventually work on reclamation of land alongside the canal that was flooded before the water could be shut down. Preston said the canal water typically runs at 1 mph., so when the breach happened and water was shut off 13 1/2 miles away, that means that water continued to flow into the breach for more than half a day.
Preston said growers along the 85 miles of dry canal in Wyoming and 45 miles in Nebraska have been patient, but he understands their concerns.
“They’ve all been very civil and understanding,” Preston said. “They’re edgy and frustrated. Their livelihood is on the line. Their family’s livelihood is on the line, their childrens’ education, but they’ve all been very understanding. ... When your future is on the line, it’s easy to be frustrated.”
There has been no determination of what caused the tunnel to fail, but that will come at a later time.
“It would be easier to be mad if somebody was at fault,” Preston said. “Right now, we’re just trying to understand the whys and what-fors.”
Through the situation, Preston said there are too many people who have helped to be able to sufficiently thank all of them. The public has established funds for donations and people have brought food to the site for the construction crews, and Preston said he was thankful for all of the businesses, the Bureau of Reclamation, the irrigation districts, the State of Wyoming and all of the contractors for their work on the project.