Lewis River

Project Overview

Merwin dam

PacifiCorp’s 510 megawatt (MW) capacity Lewis River hydroelectric facilities are located in rural southwestern Washington. The first dam site, Merwin, is approximately 10 miles east of Woodland, about 40 miles northeast of Portland, Ore. Constructed between 1931 and 1958, the Lewis River projects are located in a scenic area near Mt. St. Helens in the Cascade mountain range. View fact sheet (PDF).

Click on the construction link above for information on closures.

Springing from Adams Glacier on Mt. Adams, the North Fork of the Lewis River flows past the southern flank of Mt. St. Helens on a 90-mile path before emptying into the Columbia River near Woodland, Wash. Much of the drainage basin of the North Fork of the Lewis River lies within the Gifford Pinchot National Forest and the Mt. St. Helens National Volcanic Monument. Consequently, several state and federal resource agencies are involved in resource management in the project's vicinity.

The sequence of the four Lewis River projects upstream of the confluence of the Lewis and Columbia rivers is: Merwin, Yale, Swift No. 2, and Swift No.1. These four projects are licensed separately by FERC. Merwin (FERC No. 935), Yale (FERC No. 2071), and Swift No. 1 (FERC No. 2111) are owned and operated by PacifiCorp. Swift No. 2 (FERC NO. 2213) is owned by Cowlitz County PUD No. 1 and is operated in coordination with the other projects by PacifiCorp.

Placed in service in 1931, the Merwin project has a generating capacity of 136 mw. The dam associated with this plant is a 313-foot high concrete arch type. It creates Merwin Lake, a 4,040-acre impoundment popular with a wide variety of recreationists.

The Yale project was completed in 1953. It features a 3,780-acre reservoir (locally known as Yale Lake, it also is a popular recreation site) and a main earthfill embankment dam that is 323 feet high. The two turbines in the Yale powerhouse were recently upgraded to a combined rated capacity of 134 mw.

At 240 mw, Swift No. 1 is PacifiCorp’s largest hydroelectric facility. When initially built in 1958, the 512-foot Swift Dam was one of the highest earthfill dams in the world. The Swift Reservoir is 4,600 acres and similarly provides a variety of fishing, camping, swimming and other recreation. The discharge of Swift No. 1 enters a canal that transports the water through the 70 mw Swift No. 2 project owned by Cowlitz County PUD No. 1 before it is returned to the upper end of Yale Reservoir.

PacifiCorp operates several recreational facilities associated with the Lewis River projects. These facilities include 318 camping sites, 268 picnic sites, several boat ramps, swimming beaches, fishing access, and day use areas.

Project Contacts

Todd Olson
Director, Compliance
825 NE Multnomah Street, Suite 1800
Portland, OR 97232
(503) 813-6657

Kimberly McCune
Sr. Project Coordinator
825 NE Multnomah Street, Suite 1800
Portland, OR 97232
(503) 813-6078