128th Street in Pierce County will be widened from two to four lanes to accommodate a new arterial that will serve a large masterplan community near Orting, WA. A new two lane bridge will be constructed parallel to and downstream from the existing 128th Street bridge across the Puyallup River.
Role/Services: WSE’s work included estimating peak design discharges and developing a HEC-RAS 1D and 2D hydraulic models to evaluate performance of the existing and proposed crossings and to evaluate zero-rise requirements. WSE worked with designers to refine plans to minimize impacts to the river and habitat. WSE also developed scour and erosion countermeasures and supported the permit efforts.
Challenges/Outcome: The most significant challenge was to achieve zero-rise without adding significant project elements and costs. WSE was able to achieve a preliminary hydraulic design for the bridge that satisfied zero-rise. Final bridge design is underway.