Des Moines Marina Maintenance Dredging

Des Moines, Washington

Why It Matters

The Des Moines Marina requires periodic maintenance dredging to address shoaling and preserve safe, reliable vessel access. Sediment accumulation within the marina and entrance channel can restrict navigation and disrupt marina operations. Because dredging occurs near existing marine structures, outfalls, and active moorage, the work carefully accounts for access constraints, shoreline and slope stability, environmental requirements, and ongoing vessel use.

Project Impact

Anchor QEA has supported maintenance dredging at the Des Moines Marina across multiple events, leading sediment characterization, permitting, dredging and disposal design, bid support, construction management, and environmental compliance monitoring. The work restored navigable depths while maintaining marina operations and meeting local, state, federal, U.S. Army Corps of Engineers, and Dredged Material Management Program requirements. The team also evaluated shoreline, slope, and structural stability and coordinated dredging around existing vessels and concurrent facility improvements.

Innovations

As one of the first projects permitted under the Salish Sea Nearshore Programmatic, the project demonstrated an approach now widely used across Puget Sound. To mitigate dredging impacts, Anchor QEA worked with the City remove creosote piles and overwater cover and replace other derelict marina piles. This coordinated strategy offset impacts while enabling needed marina maintenance.

Careful characterization and sequencing were critical to completing dredging efficiently. The team developed a sediment sampling strategy that secured open-water disposal determinations while isolating known contaminated areas for upland disposal, reducing cost impacts. Dredging phasing maintained vessel access, and mechanical and hydraulic methods were selected to work within constrained areas of the marina.