Three drop structures

Community unites to restore river function

About the Project

The Long Tom River flows east from its headwaters in the Central Oregon Coast Range to join the Willamette River. In 1941, the U.S. Army Corps of Engineers (the Corps) built Fern Ridge, a flood control and water supply dam, in the upper watershed, and in the lower watershed, straightened the Long Tom River and armored the channel. This work converted a 36-mile reach of meandering river into a straighter, deeper, 23-mile stretch. The Corps also built three low-head dams to slow the river’s velocity and reduce scour. All three barriers, also known as drop structures, block fish passage.

The lower watershed of the Long Tom River is important juvenile rearing habitat for Willamette River system salmon and steelhead, as well as lamprey. The Confederated Tribes of Siletz Indians are restoring important salmon rearing habitat in Oregon’s Willamette Valley.

The first barrier facing fish on Long Tom is the Monroe Drop structure, an 85-feet-wide, 9.5-feet-tall concrete dam located near the City of Monroe, which creates a small lake that is a safety hazard for the city. Removal of the Monroe Drop is precondition for the other projects. Upstream is the Stroda Drop structure, which sits adjacent to property of a private landowner willing to install effective fish passage if the Monroe Drop is improved or removed first. A few miles further upstream is the Ferguson Drop structure, which also hinders fish passage. Removal of or improvements to these three structures would give juvenile fish access to 106 miles of additional mainstem and tributary habitat.

In 2019, the Corps began a Continuing Authorities Program under Section 1135 of the Water Resources Development Act of 1986 to evaluate options for modifying the Monroe Drop structure to enable fish passage. Funding constraints, however, slowed progress. The Siltez Tribe is a non-federal co-sponsor of the Section 1135 process.

FACTS AT A GLANCE
Owner: U.S. Army Corps of Engineers
Size: 3 low-head dams between 7.5 and 11.5 feet high
Project Cost: $3.38 million
ORF Investment: Project scoping, conceptual design, and public outreach
Miles Opened: 106 miles
Fish: ESA-threatened spring Chinook, two species of lamprey, Oregon chub, cutthroat trout, western pond turtles, red-legged frogs, redside shiners, dace, sculpin, and stickleback
Status: Construction anticipated 2025


RESOURCES
OUTCOMES
  • Restore access for juvenile salmon and cutthroat trout to 106 miles of mainstem and tributary habitat
  • Improve access for ESA-threatened spring-run Chinook salmon and two species of lamprey, and improve conditions for cutthroat, Oregon chub, dace, sculpin, and other native fish species
  • Eliminate the safety hazard from the low-head dam and backwater lake in the town of Monroe
  • Enhance the aesthetic appeal and recreation potential of the Monroe waterfront business area

Project Partners

Long Tom Watershed Council

Confederated Tribes of Siletz Indians

City of Monroe

Oregon Watershed Enhancement Board

U.S. Army Corps of Engineers