Manley Road Repairs Clark County, Washington

A combination of important roadway safety improvements and stream habitat enhancements provided the basis for repairs to Manley Road. With steep grades, sharp turns, and short sightlines, the existing roadway crosses Daybreak Creek at multiple locations where undersized culverts blocked fish passage to important upstream habitat. Otak worked as an extension of Clark County Public Works staff by providing stream, structural, and environmental permitting to ultimately benefit both driver safety and fish habitat for species including Endangered Species Act (ESA) protected salmonids.

Complex Stream Enhancement Design Meets Road Safety Improvements

In replacing the four undersized culverts, a multidisciplinary design process was established that included analysis of hydraulics, geomorphology, and habitat. Environmental permit approvals were also obtained while working in a stream with ESA protected species. Along with the design of replacement crossings was the opportunity for 750 feet of stream enhancements, all of which overcame unique challenges including: low cover at the crossings, steep channel slopes, dynamic lateral channel movement, and a failing roadway embankment. These enhancements improved the habitat conditions through bottomless culverts, detailed cascade-pool channel design, and bioengineered bank stabilization techniques. More than 3,000 plants were also added as part of the planting design. For an area prone to traffic accidents, roadway safety improvements adjusted the horizontal and vertical alignment of Manley Road while also addressing required stormwater management facilities.