| Tunnelling
bypass tunnels, Switzerland was the perfect focal point for the USACE team to pursue more knowledge and see Swiss dam infrastructure up close. As Cameron McLeod from the USACE explains, staff
from the Alaska District, Seattle District, and Omaha District toured the inner workings of the Pfaffensprung sediment bypass tunnel, which is part of a dam that impounds the River Reuss. This system has been in use for over 100 years and has employed granite pavers in the lining of its tunnel because, when compared with other materials, granite is considered to be more resilient. The team also visited the sediment bypass tunnel at Solis Dam in the nearby canton of Grisons. Like the dam at Pfaffensprung, Solis is a hydropower-producing dam and is of a similar design to Lowell Creek project. And as Swiss university ETH Zurich is currently conducting a study of abrasion upon different kinds of pavers in the Pfaffensprung and Solis tunnels, researchers here also shared valuable insights with the USACE team. McLeod reports that granite pavers stood out as the “winning formula” for the dams in Switzerland, and the USACE group learned extensively about their characteristics and life cycle on their trip. The more expensive, granite pavers were considered to be more cost-effective in the long run due to their comparative durability, and is why USACE says it is “definitely leaning in that direction back home in Alaska.” The UASCE team says the trip provided them with helpful lessons which will prove to be invaluable going forward, and better equip them to design the project at Lowell Creek.
Above: The Pfaffensprung sediment bypass tunnel is visible from above the dam and the outlet. This infrastructure has been in use for over 100 years and continues to provide flood protection and hydropower for the surrounding communities. (Photo by Carly Lynch, USACE – Alaska District)
Left: USACE staff investigate the Pfaffensprung sediment bypass tunnel in Switzerland. This critical piece of infrastructure flushes material from the dam’s pool, which can include sediment and larger matter. (Photo by Jesse Brown, USACE – Huntington District)
Left: A Swiss engineer investigates a worn area in the Solis sediment bypass tunnel. At about 18ft by 18ft, this tunnel is nearly the same size as the proposed dimensions for the upcoming project at Lowell Creek in Alaska. (Photo by Carly Lynch, USACE – Alaska District)
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