News Release
| Release Number: | 00-107 |
| Dated: | 6/19/2000 |
| Contact: | Public Affairs Office, 503-808-4510 |
Portland, Ore.—The U.S. Army Corps of Engineers has issued a document (Statement of Findings) summarizing public comments and decisions regarding its five-year annual maintenance dredging plan for the Columbia River Federal Navigation Channel.
The original dredging proposal, issued in February 2000, was reissued in April with clarifying statements to address comments heard at an April 4, 2000, public meeting in Astoria, Ore. Follow-up meetings were held with the Washington Department of Ecology and the Oregon Department of Environmental Quality to discuss those comments and assure interagency agreement. Both agencies have issued water quality certifications.
The final maintenance dredging plan covers annual dredging in the Columbia River from river mile 3 near Astoria, Ore., to river mile 106.5 near Vancouver, Wash., from 2000 through 2005. In an average year, about 35 miles of the total channel length must be dredged and an average of about 4 million cubic yards to 6 mcy must be removed. The channel is maintained to its authorized 40-foot depth and 600-foot width. The dredging work is done by pipeline dredge, clamshell dredge, or the Corps’ hopper dredges. Dredging in the federal navigation channel can be done year round to prevent hazardous shipping conditions from developing, but normally occurs from March 1 through Nov. 30 each year.
The Statement of Findings and the water quality certification information from both agencies are available at the Corps’ website: the Statement of Findings, https://www.nwp.usace.army.mil/op/n/CLW_SOF1.pdf; and the water quality certifications, www.nwp.usace.army.mil/op/n/waterquality.pdf. Both also are available for viewing or copying in the Corps’ Portland District Library, 333 SW First, Portland, Ore.
Until the Environmental Protection Agency designates permanent ocean disposal sites, none of the material dredged during annual channel maintenance work will be placed in the ocean. It is possible that none of the dredged material covered under the current five-year plan will be placed in the ocean. Flow lane disposal, in which dredged material is placed back in the river in areas which are generally between 45-feet and 65-feet deep, and either within or adjacent to the federal channel, will be used. Flow lane disposal is necessary because there are no disposal sites on land or on the shoreline in many areas where shoaling must be removed each year. The material has been evaluated according to Clean Water Act guidelines, and determined to be suitable for unconfined open water disposal.
Monitoring by the National Marine Fisheries Service (NMFS), the U.S. Geological Survey (USGS) and the Corps, indicates levels of turbidity, dissolved oxygen and sediment transport from flow lane disposal cause minimal impact to water quality in the river. Additional studies are planned with state and federal fisheries agencies to examine the potential effects of flow lane disposal on white sturgeon.
The dredging and disposal of the material will be done in accordance with the recently coordinated Dredged Material Management Plan for the Columbia and Lower Willamette River Federal Navigation Channel. The dredged material will be placed in sites used in the past that have already been evaluated and approved by the National Marine Fisheries Service and other resource agencies for this purpose.
Emergency dredging began in the Columbia River near Longview, Wash., on June 6. The dredge Oregon, operated by the Port of Portland, and the Corps’ dredge Essayons began the dredging season removing shoals that created hazardous shipping conditions in that area.
Annual maintenance dredging is not related to the Columbia River Channel Improvements Project.