USACE Analyzes Dredge Material Usage on the Lower Columbia River

The U.S. Army Corps of Engineers, Portland District (USACE) developed an environmental analysis in accordance with the National Environmental Policy Act of 1969, as amended. The Final Environmental Assessment (EA) dated 30 September 2022, for Lower Columbia River Navigation Channel Dredged Material Transfer Site (W-60.9-IW-T) addresses the project purpose to provide an in-water holding area for temporary storage of dredged material from the lower Columbia River (LCR) federal navigation channel (FNC) and then re-dredge the material and deposit it permanently in an existing upland placement site. The project is located near river mile 60 in Cowlitz County, Washington.

USACE prepared a Finding of No Significant Impacts (FONSI) under the authorities as outlined below. Congress authorized USACE to construct and improve federal navigation projects over time. Generally, Congress authorizes federal navigation channels by specific dimensions (depth and width). Congress has specifically authorized construction of, and improvement to, the LCR FNC by the Rivers and Harbors Acts (RHA) of 1878, 1892, 1902, 1912, 1930, and 1962, and most recently the Water Resources Development Act (WRDA) of 1999 and Consolidated Appropriations Act of 2004. Implicit in Congressional authorization to construct is a USACE non-discretionary duty to continue operating and maintaining project features.

Congress also provides USACE with annual appropriations for LCR FNC operation and maintenance activities. In carrying out LCR FNC maintenance dredging and placement activities to meet authorized dimensions, USACE complies with Sections 102 and 103 of the MPRSA of 1972, Sections 401 and 404 of the CWA of 1977, and regulations at 33 Code of Federal Regulations (CFR) parts 335 through 338 (“Operation and Maintenance of Army Corps of Engineers Civil Works Projects Involving Discharge of Dredged or Fill Material into Waters of the U.S. or Ocean Waters” and affiliated procedures, etc.). USACE determined the Final EA, incorporated herein by reference, appropriately assessed, and disclosed the environmental impacts of the reasonable alternatives considered in the EA including the Proposed Action. The proposed action, which is the preferred alternative, includes improvements to the management of the Lower Columbia River Federal Navigation Channel (LCR FNC) by adding one new transfer site to the existing dredged material placement Network. Material dredged during routine maintenance of the Lower Columbia River federal navigation channel will be placed temporarily in-water at the transfer site (W-60.9-IW-T) and then re-dredged and transported by USACE to the existing Hump Island upland placement site (W-59.7-UP).

USACE also considered a no action alternative. Under the no action alternative, USACE would not construct or use the constructed proposed transfer site and dredged material would likely not be placed in the accompany existing upland and shoreline placement site. The no action alternative would disrupt the planned use of the temporary placement site and a USACE balanced approach to placement in the Columbia River flowlane and in the network of upland and shoreline placement sites. To maintain the LCR FNC as Congressionally authorized, more dredged material would have to be placed back into the flowlane permanently, instead of ultimate placement upland or along the shoreline (which the transfer site enables). The additional material permanently placed back into the flowlane would likely be transported by river processes back into the LCR FNC as shoaling, which would then increase the amount of annual dredging required. Increased annual dredging would result in increased costs, and also dredge equipment has limited availability, so the additional shoaling would restrict shipping traffic in the LCR FNC.

The draft EA was made available for a 15-day public review period, from August 19 through September 2, 2022. The Corps requested comments from federal and state agencies, as well as interested parties including interest groups and tribes. One comment was received from the Environmental Protection Agency (EPA). As a result of state and agency review, the final EA was revised to incorporate the relevant recommendations of EPA.