As part of realigning the state routes and redeveloping downtown, the city decided to take a holistic approach to their downtown revitalization and daylight Horse Creek along 98th Avenue NE as a public amenity. Horse Creek was piped under the downtown area before discharging into the Sammamish River. PACE led a multidisciplinary design team to daylight approximately 3,000 LF of the stream; relocate and reconstruct five blocks of roadway; design new water, sewer, and storm utilities; and design numerous public amenities and several pedestrian bridges.
Key design aspects included 10 fish-passable culverts approximately 675 feet in length and up to 18 feet wide; basin modeling for an 800-acre drainage basin; stormwater conveyance analysis of the downtown business district; design of a stable stream channel in a flashy urban environment (flows range from 0.25 cfs to 100 cfs); containment and disposal of contaminated soil and groundwater within the project area; securing environmental permits from the U.S. Army Corps of Engineers (USACE), Washington State Department of Fish and Wildlife, and concurrence from the tribes; and filling and abandoning the existing Horse Creek pipe and channel, including the design of required mitigation.
PACE was involved in coordinating with the Northshore School District and downtown developers in designing solutions to not only solve flooding and habitat issues but also create public/private partnerships for the city to achieve the vision for their downtown redevelopment.