Dredging

Over time, sediment builds up along the Columbia-Snake River System and navigation channel maintenance in the form of dredging is required to ensure safe passage for barges and cruise ships.

The US Army Corps of Engineers is congressionally authorized to maintain a 14’ deep by 250’ wide navigation channel on the Columbia-Snake River System. Sediment management plans follow federal guidelines and are issued from the USACE prior to dredging activity.

Recent dredging of the Snake River Channel took place in 1999, 2006, 2015 and 2023.

In November 2014 the USACE issued two Records of Decision in advance of maintenance dredging for the Lower Snake River. The first was for the long-term Lower Snake River Final Programmatic Sediment Management Plan and the second was for a current “immediate need” action (dredging) to re-establish the congressionally authorized dimensions of the Lower Snake River federal navigation channel.

Areas in need of dredging at the time included the downstream lock approach at Ice Harbor Dam and the confluence of the Snake and Clearwater rivers at the upstream end of the Lower Granite Reservoir, as well as berthing areas at the Ports of Lewiston and Clarkston.

Few rivers are naturally deep and free of sediment build-up, therefore maintenance dredging is a commonplace activity. According to the USACE, more than 400 ports and 25,000 miles of navigation channels are regularly dredged throughout the U.S.

Even though dredging is a regular activity for our country’s marine highways, dredging sometimes meets with legal challenges. This was true of the most recent effort to dredge the Lower Snake River channel.

However, the 2015 legal challenge was quickly dismissed in court. On January 5, 2015, Judge James Robart of the U.S. District Court’s Western District of Washington, ruled in favor of the federal government and denied an injunction to halt dredging on the Snake River. On Feb. 9, 2016, Judge Robart ruled unequivocally in favor of the federal government and dismissed the merits portion of the Snake River Programmatic Sediment Management Plan lawsuit.

In 2015, after nine years without maintenance dredging, the local river channel was returned to a safe depth of 14′. The work was done during the USACE’s annual in-water work window, Dec. 15-Feb. 28. This is when salmonid fish are less likely to be present in the water.

According to the USACE, dredged materials were used to construct additional shallow water fish habitat near Knoxway Canyon, about 23 miles downstream of Clarkston, Washington.