FORT LARAMIE, Wyo. — A second hole in the top of a collapsed tunnel that has closed the Gering-Fort Laramie Irrigation Canal is larger than the first one crews encountered.
Officials say they have reached the second hole and estimate it is about 4 feet wide, and they are yet to determine its length.
“We’ve moved up a little bit, and we’ve advanced to 6 or 8 feet past the beginning of that second hole in the roof,” James Byrd, operations manager-underground division for SAK Construction, said Monday. "That hole appears to be wider than the first one, but we’re not sure just yet how much longer it is because we just can’t see all of it yet.”
Crews have been working at the site of the July 17 collapse of a 2,200-feet long tunnel that caused a canal breach, forcing the Bureau of Reclamation to shut down delivery of irrigation water. The collapsed tunnel 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.
At this point, there is no timetable for completion and the return of water to the canal. Crews inside the tunnel have worked to about 690 feet into the tunnel. Byrd said the center of the sinkhole above the second hole was at 675 feet, giving them their initial view of the larger hole in the concrete. That said, setting an estimate for the return of water is still not possible.
“We just can’t tell because we won’t know what the concrete looks like until once we can get in there,” Byrd said.
As excavation crews from the irrigation districts work above the tunnel to remove sand and dirt, crews from SAK are working inside the tunnel to shore up the interior walls and remove debris to clear the path. Monday morning, crews had reached approximately 25 feet above the top of the tunnel as they work to get close enough to install a series of shoring boxes over the top of the tunnel to take pressure off the concrete walls. The boxes were placed Monday night and the crews will work Tuesday to begin installation.
“That concrete is in a very precarious position,” Byrd said. “Right now, we’re having to work on keeping the concrete up, not just removing the sand from inside.”
Gering/Fort Laramie Irrigation District General Manager Rick Preston said the work is moving very slowly to ensure the safety of the workers.
“In addition to the larger hole, there are cracks down the side that we have to get shored up,” he said. “It’s all very tedious right now.”
With the excavation crews getting close enough, the shoring boxes can be pieced together and installed. Unfortunately, with the excavating being done so close to the top of the tunnel, the vibration from the machinery causes a hazard for the crew inside the tunnel, making them unable to work at the same time.
“Hopefully (Monday) we can get the final piece of that dirt work done,” Preston said. “Then we can bring down those shoring boxes from on top of the hill and get them ready to be set. Hopefully, by mid-week we can set the shoring boxes and those guys inside can get a little more aggressive with what they have to do.”