|New Levee Successfully Holds Back Major Flood|
in Orting, Washington
The newly constructed Calistoga Levee, on the Puyallup River in Orting, Washington, was recently put to the test with a major flood and kept the city dry. The flood, involving a large flow of 16,300 cubic ft per second, was the fourth largest since 1962 and had major potential to damage homes and businesses.
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The City of Orting is located between the Puyallup and Carbon Rivers, in Pierce County. Flooding hazards increasingly pose a threat to lives and property as Orting and the surrounding area continue to develop. Seven federally declared flooding disasters have impacted Orting since 1990, often initiating flood fighting procedures by residents, the City, Pierce County, and the U.S. Army Corps of Engineers.
NHC was retained to assist the City with design of a new setback levee. NHC developed a hydraulic model of the river to determine the appropriate levee footprint and height. We conducted sediment transport modeling to predict gravel aggradation that could be expected in a 15 and 30 year time horizon. We also predicted future channel alignment for the design. NHC designed the riprap armoring, habitat enhancement, and bank roughening features for the entire setback region. This work included placement of 22 engineered log jams, 1.5 miles of rock riprap armoring, and 2000 feet of a habitat bench strengthened with salvaged logs. In the summer of 2014, NHC staff provided construction management services to the City, overseeing placement and construction of all wood structures and habitat elements. NHC's contribution to the final design not only helps protect the City from flooding, but also provides fish refuge by adding habitat features and reconnecting the Puyallup River to the historic floodplain.
Following the recent heavy rains and flood event, City of Orting Building Official Ken Wolfe reported, "Your structures didn't budge an inch! Nicely engineered gentlemen!”. The project team, led by Chris Long and Erik Rowland, included technical experts from NHC offices in Seattle, Sacramento, and Vancouver. As Erik noted, "Chris and I echo Ken Wolfe's excitement with how well this design performed. The project success was due to effective collaboration among NHC's staff Darren Hinton, Todd Bennett, Derek Ray, Brad Hall, Brady McDaniel, and many others. As such, this serves as a great example of NHC pooling our resources to provide the very best in engineering analysis, design, and construction support”. As one of the interviewed Orting residents noted, "The levee held. The levee's new and it rocks”.