The competition recognizes companies that have completed difficult projects with innovation and efficiency with outstanding results.
The project required improvements to the slopes of the Pilchuck River in Washington, which had severely eroded. The erosion had resulted in mud slides that had destroyed one home and were an imminent threat (40 ft) from shutting down SR92. The work included installing a temporary diversion of the river, constructing a rock revetment, installing large woody debris structures, root wads, coir encapsulated soil lifts and final planting.
Diversion of the Pilchuck River was the greatest challenge on this project, as it would require a dam that was versatile in segment lengths and for the depth of water it would retain. Although the average stream depth at the time of installation was only 1.5 ft, Marshbank selected an 8-ft-tall Aqua Dam to allow for the change in depth the dam to narrowed the river’s width. The dam’s depth also needed to allow for potential summer rainstorms, which would increase the flow in the diverted channel. The company selected the correct size, as one large storm raised the river within 6 to 12 in. of overflowing the 8-ft dam.
Marshbank partnered with the Washington DOT (WSDOT) to allow a stream diversion outside the anticipated channel, which required the approval of multiple agencies, including the Dept. of Fisheries, Dept. of Ecology and multiple tribal agencies. Due to the short window of time for completion, Marshbank was given approval by all agencies within a week.
The timely completion of the project prevented the loss and/or disruption of SR92, which carries a daily average of more than 15,000 cars. The improvements to the river slope also prevented the slide loss of two additional homes. The installation of large woody debris and root rods, which were part of the repair, provided for enhanced fish habitat.
The project was rewarding for both WSDOT and Marshbank Construction; WSDOT project engineer David Lindberg said, “We look forward to working with Marshbank on future projects.”