The Walla Walla District recently completed dredging work at the confluence of the Snake and Clearwater rivers near Lewiston, Idaho and downstream of Ice Harbor Dam. This is the first project the district has completed using Bipartisan Infrastructure Law funds.
The commitment of Walla Walla District engineers and designers was essential to the overwhelming success of this project. The project delivery team received funding in April 2022, with the goal that dredging would occur during the next in-water work window, which ended March 1, 2023.
The team worked diligently to design the project, collecting incredibly accurate data for contractors, and taking steps to ensure strict environmental standards were met. The effort, which should’ve taken over a year to complete, had a contract awarded by the end of September 2022.
The overall attention to detail resulted in a project that was delivered successfully and $3 million under budget.
Dredging is an important mission for the Walla Walla District, enabling free movement on waterways. This dredging work provided necessary maintenance for the federal navigation channel, which must be maintained at a depth of 14 feet. The Walla Walla District also worked in coordination with stakeholders along the navigation lanes. These stakeholders were able to use the contractor mobilized by the Walla Walla District to perform necessary dredging at their facilities at their expense.
These additional dredging locations included the Clarkston Crane Dock Maintenance Area, the Clarkston Grain Dock Maintenance Area, the Clarkston Recreation Dock Maintenance Area, the Clarkston Cruise Line Dock Maintenance Area, and the Lewiston Grain Dock Maintenance Area.
During the design phase of the project, Walla Walla District engineers used bathymetry data from 2016 and 2021 to provide estimates of how much sediment needed to be removed in the target areas. These estimates were used to inform contractors when putting the project up for bid.
The estimate used for the contract was 218,980 cubic yards of sediment. After work was completed, the final quantity of sediment removed totaled 218,286 cubic yards, a difference of only 0.3%.
Before the actual dredging began, multiple surveys were performed to determine the potential environmental impacts of the project.
“We performed surveys of the areas to be dredged for fall Chinook salmon nests and young lamprey. The water clarity was high, and we were able to determine there would be little to no impacts on these resources from the dredging,” Benjamin Tice, a biologist for the Walla Walla District, said.
All Washington State water quality standards were met throughout the project. The Walla Walla District worked in coordination with multiple agencies to ensure environmental compliance, including the National Marine Fisheries Service, the United States Fish and Wildlife Service, the Washington State Department of Ecology, the Idaho Department of Environmental Quality, the Washington Department of Fish & Wildlife, and the Nez Perce Tribe. By working together with our partners and stakeholders, we can find innovative and effective solutions that balance economic, social and environmental priorities.
The actual dredging began on January 5, and the contractor removed 218,286 cubic yards of sediment in less than 60 days, in 144 scow loads. This sediment was disposed in-water at a site near Bishop Bar. Work was completed before March 1, before the spring fish runs.
“It is often overlooked that responsible stewardship of the natural and non-natural resources we are entrusted with is an intrinsic part of our commitment as engineers and designers. Good design serves to ensure proper use of the resources we have been blessed with to meet the needs of society while safeguarding those resources for continued use. I believe this project serves as a good demonstration that shows we can effectively utilize our natural resources responsibly and exercise good stewardship to preserve those resources for future generations,” Frank Wachob, a civil engineer for the Walla Walla District, said.
The last dredging work done in these areas was performed in 2015, eight years ago. Historically, dredging for channel maintenance has been conducted every three to seven years.
The Walla Walla District will continue to invest in the best technology and practices to ensure the highest quality services. The district has many more projects funded by the Bipartisan Infrastructure Law, including the ecosystem restoration of Clover Island. The ribbon-cutting ceremony for Clover Island will be held on May 12.