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CIPP Rehabilitation of Sewers in the Beaver State – Design, Construction, and Lessons Learned
Author: Vanessa Adams, Robert K. Lee, John D. Kennedy
Date: 4/912
Preprint, North American Society for Trenchless Technology (NASTT) No-Dig Show 2012, March 11-15, 2012, Nashville, TN

As the name “Beaver State” suggests, areas of the state of Oregon are populated by beavers and as these beaver populations continue to thrive, portions of the sewer system that were previously in relatively dry stream corridors are now in wetland areas. Clean Water Services, which owns and operates the 2nd largest collection system in Oregon, identified a 21-inch trunk sewer that had operational issues and structural concerns. Site visits revealed that the manholes along the sewer, once located in an open field, were now under 6-inches of water even in summer months. Further investigation revealed that the stream corridor had rapidly changed in the last couple of years due to erection of several beaver dams. Not wanting to abandon the rehabilitation work that seemed even more imperative, questions arose as to how to design and construct the work. This paper discusses the concerns raised by a public agency on the legality of altering beaver dams in an environmentally sensitive area, the evaluation and selection of trenchless technologies, and design and development of bid documents for construction in flooded and vegetated environments. Clean Water Services proceeded with the design and construction of the project, and construction was completed in the fall of 2011.