Contact us about Dexter:
General: 541-684-4300
Recreation: 541-942-5631

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Dexter pamphlet

Dexter Dam & Reservoir

Dexter Dam

Project Description
Dexter Dam is located on the Middle Fork Willamette River in Lowell, Oregon and 20 miles upstream of Eugene and Springfield, Oregon. Dexter Dam is a 90 ft tall, 2,319ft long rockfill earthen embankment dam with a 359 ft long concrete spillway equipped with seven spillway gates, regulating outlet, and a powerhouse. Dexter Dam is owned, operated, and maintained by the Portland District of the U.S. Army Corps of Engineers (USACE). Construction of the dam began in 1947 and was completed in 1955. Dexter Dam is part of a system of 13 multi-purpose dams in the Willamette Valley with the primary purpose of flood risk management and secondary purposes of hydropower, recreation, irrigation, municipal and industrial water supply, fish and wildlife, and water quality. Collectively, this system of dams is referred to as the Willamette Valley Project.

Dexter Dam is 1 mile downstream of Lookout Point Dam. Dexter Dam is a re-regulating dam for Lookout Point and is operated to provide consistent flows into the river downstream while allowing for fluctuations in outflow from Lookout Point Dam.  The re-regulation of flow allows for Lookout Point Dam's powerhouse to meet peak electricity demands on a daily basis for the region.

Dexter Dam is located about 70 miles east of the Cascadia Subduction Zone a megathrust fault along the Oregon Coast. The Cascadia Subduction Zone is capable of producing very large, long duration earthquakes. The last Cascadia Subduction Zone earthquake occurred in the year 1700.

Risk Characterization: Low
USACE performs risk assessments as part of an ongoing dam safety program and to assist in the prioritization of investment for aging infrastructure.  The risk assessments evaluate the life safety risks associated with the dams to determine if risk reduction actions are needed and, if so, what actions should be taken.  USACE completed a routine risk assessment for Dexter Dam in June 2015 that characterizes the risk associated with the dam to be Low. The assessment considered a wide range of hazard scenarios from the most likely to the most extreme and unlikely.  The assessment considered several scenarios that could be damaging to the structure and the embankment driven by an earthquake and or by extreme flood events. For all the scenarios considered, the associated risks were found to be low and not to require any short-term measures or long-term modification.

USACE is confident that the Willamette Valley dams are well-built, well-maintained, and will continue to significantly reduce flood risks for the region. However, the dams cannot eliminate potential for flooding. Even with the presence of the Willamette Valley dams, extreme rainfall and snowmelt events may result in flooding in areas downstream of dams.  Flooding can be caused by high flows resulting from unregulated portions of the watershed and/or high flow that must be passed through the dam outlets and spillways when reservoir storage capacities are exceeded.

Risk Management Measures
USACE continues to evaluate the condition and risks associated with its dams and will continue to review the risk associated with Dexter Dam in future routine studies. USACE regularly conducts routine inspections of its dams and Dexter Dam is equipped with instrumentation to monitor dam performance and seismic activity. Post-earthquake procedures are in place to inspect and evaluate earthquake damages and USACE conducts routine dam safety exercises with local Emergency Managers and first responders. Dexter Dam’s Emergency Action Plan (EAP) outlines actions to be taken during an emergency. USACE will update the EAP based on recent risk assessment results and information from updated inundation maps. In addition, USACE will continue and increase its outreach to improve community awareness of flood risks and risks associated with the dam. 

View more details about Dexter Dam at the National Inventory of Dams website.

Dexter recreation

Birding: Dexter lake and shoreline lands total about 1,300 acres. The northeast shoreline provides a mosaic of quality wildlife habitat that supports migratory and resident songbirds, osprey and eagles. The reservoir is a designated stop along the McKenzie Loop of the Willamette Valley Birding Trail. This trail is a self-guided driving itinerary that includes 138 birding hot-spots.

Day-use parks: Dexter lake has three day-use parks.
• Orchard Park, is operated by the U.S. Army Corps of Engineers and has no associated fees.
Open: mid May - mid Sept.and closed daily from dusk until 8:00 a.m.
This minimally developed park is located on the northeast end of the lake and includes a vault toilet and picnic tables. There are no group picnic areas or shelters available for reservations. For more information, call the Willamette Valley Project Park Ranger Office at 541-942-5631.

•Dexter Park and Lowell Park are operated by Oregon State Parks.
Call the Oregon State Parks office at 541-937-1173 or click one of the links for more information:Dexter Park; or Lowell Park. Lowell Park also has a life jacket loaner station* available.

*Loaner life jackets may not be available due to COVID-19. Be prepared and bring your own.‚Äč

 

Getting around

Dexter recreation map 

Environmental stewardship at Dexter Dam

Stewardship projects include wetlands restoration and management of invasive species. Restoration of degraded uplands, wetlands and streams on Corps lands is a central focus of the Willamette Valley Environmental Stewardship program. Recent efforts to improve habitat quality for wildlife on Corps’ lands in these areas center on replacement of exotic and invasive plants with native trees and shrubs, and restoration of hydrology and topography to support native plant communities and wildlife habitat.

To mitigate impacts of Corps dams on Chinook salmon and the Middle Fork of the Willamette River, the Corps constructed the Willamette Fish Hatchery near Oakridge and the holding ponds downstream of Dexter Dam. These facilities are operated by the Oregon Department of Fish and Wildlife with funds provided by the Corps. Additionally, the Corps supports ongoing efforts for the recovery of the Oregon chub and bull trout within the Middle Fork Willamette River basin.

Flood risk management at Dexter Dam

Conservation season - April to November: Restrict pool elevation to 690 feet.
Flood season - November to March: Restrict pool to 690 feet.

For more information, visit our Water page.