Saltwater State Park Bridge Seismic Retrofit
City of Des Moines
Des Moines, Washington
Exeltech provided project management, civil and structural engineering, environmental permitting, and construction management and inspection services for the seismic retrofit of this FHWA-funded bridge that carries Marine View Drive South over Saltwater State Park. The eight-span bridge is 570 feet long with a 24-foot roadway width. The superstructure is a cast-in-place reinforced concrete double-tee with two-column bents. A three-dimensional computer model was used to analyze seismic demand and a non-linear pushover analysis was completed to estimate the capacities of the bridge substructure components.
The tall, slender piers of the historically significant Saltwater State Park bridge mimic the timbers of the McSorley Creek ravine. While the bridge looked timeless, the City of Des Moines recognized that the stately 1934-built bridge was in desperate need of attention. Originally planned as a two-phase retrofit, Exeltech understood the urgency of the bridge repair and recommended an approach that accomplished the retrofit within a single phase, and within a single funding cycle. Combining phases allowed a streamlined design and construction approach that incorporated required safety measures and extended the life of this iconic bridge. Exeltech’s design solution wrapped the piers with carbon fiber reinforcement to extend the life of the structure while maintaining original aesthetics. The design took into consideration adjacency to McSorley Creek and minimized impacts to the stream and trees.
Exeltech coordinated environmental permitting through Washington Department of Fish & Wildlife and US Army Corps of Engineers, taking advantage of Habitat Enhancement Hydraulic Project Approval. Permitting included the Section 4(F) requirements of NEPA, which protects significant publicly owned parks as well as significant historic sites.
The project was honored with the 2016 APWA Washington Chapter Project of the Year Award (structural, under $25M) and 2016 ACEC Best in State Bronze Award for Originality/Innovation.
