Strengthening Infrastructure, Water Supply and Habitat 

The 80-year-old Nelson Dam and associated surface water intake provided irrigation water to over 8,000 residents and commercial farmers, contributing significantly to the area’s economy and agricultural success. Over time, the dam outlived its useful life and contributed to the interruption of natural river processes, diminished flood conveyance capacity and was an impediment to fish migration.

In 2011, HDR partnered with the City of Yakima and Yakima County Flood Control Zone District to help lead the planning, development and implementation of Nelson Dam’s removal and replacement. We facilitated multi-stakeholder engagements to set objectives and identify opportunities and solutions that represent key values held by project stakeholders. After ten years of development and completion of numerous studies, the selected alternative included elements targeted to improve and protect public infrastructure, increase water supply reliability and restore ecological habitat across a range of conditions experienced today and in the future.

Old fill material, debris and concrete infrastructure were removed from the river and floodplain. Fish passage is restored through a channel-spanning nature-like fishway. A new intake structure now provides a more reliable source of water meeting state and federal fish screening and protection guidelines. Floodplain grading and excavation of pilot channels now offer improved wetland connectivity and more frequent availability of spawning and rearing habitat.

Throughout project implementation, our team provided the full range of engineering analysis, environmental permitting, construction documentation and bidding support including management of an early material procurement program. Through construction completion in 2023, we acted as the owner’s representative and performed contract administrative activities, engineering services during construction, facility commissioning, and development of a comprehensive operation, maintenance and monitoring program.

The project includes the consolidation of four older diversions with a single new surface water intake and diversion system. A second phase of the project is anticipated to be completed in 2025. It will connect the new diversion with two additional distributaries and will pave the way for additional intake removal, floodplain restoration and levee setbacks as part of future projects.

The health of the community is tied to the health of our rivers, the availability of clean water and the infrastructure that protects it. By removing structures that have outlived their intended purposes and replacing them with a modern plan for managing our waterways, we can protect our economic interests in the safest and most cost-effective way possible.