Big Cliff Dam Total Dissolved Gas Project

Background
The Big Cliff Dam Total Dissolved Gas Project is initiated in response to the 2021 NEDC v. USACE injunction order, which mandates the US Army Corps of Engineers (USACE) and the National Marine Fisheries Service to enhance water quality at various USACE projects in the Willamette Valley.

The Big Cliff Dam (BCL) has been identified as a site where downstream waters exhibit elevated levels of total dissolved gas (TDG), which can be detrimental to aquatic life. The primary goal of this project is to construct a structural solution that reduces TDG levels downstream of BCL to meet the state water quality threshold of 110% saturation.

Work Details
The scope of work involves the construction of an in-water, channel-spanning, submerged rock weir downstream of BCL, along with incidental related work.

The rock weir is designed to replicate a natural riverine feature resembling a mildly-sloped riffle, aimed specifically at mitigating TDG levels downstream. Key project objectives include:
1) Abating TDG levels downstream of BCL to meet or fall below the state water quality threshold;
2) Completing the construction of a 'prototype' rock weir by October 2025, in accordance with a court-mandated schedule.

Additional constraints include: all in-water construction must occur within the window from July 15 to August 31, 2025; no machinery or man-made materials are allowed in the river; and all work must be conducted from the North shore due to access restrictions on the South shore. Challenges include ensuring that crane operations do not damage existing infrastructure and sourcing appropriate rock materials.

Period of Performance
The anticipated construction schedule indicates that advertising for bids will occur in January 2025, with contract awards expected by April 2025 and estimated completion by October 2025.

Place of Performance
The construction projects will take place at Big Cliff Dam located within the Willamette Valley.