The Lewis River Hydroelectric Projects - PacifiCorp

Lewis River Interpretive & Education Plan
several farms were purchased and their inhabitants moved to other locations.
Some residents held out for several years, until the dam was nearly complete.
Construction of the Ariel Dam (now called Merwin Dam) was begun in 1929.
Trees were felled around the margins of what would become the lake, although
the timber along the river was left standing (this was not the case with Yale and
Swift Dams, where timber was harvested throughout much of the lake’s footprint
before flooding).
Although construction of the first unit of the Ariel Dam was not completed until
1932, the tunnel that diverted water around the dam was closed as early as 1930
and water began to fill the valley at that time.
The lake and dam were renamed by H.J. Campbell, publisher of the Vancouver
Columbian, for L. T. Merwin of the Northwestern Electric Company.
Two additional projects, in 1949 and 1958, expanded the dam. Today, the
Merwin Dam is a concrete-arch dam, with a total crest length of 1300 feet and a
maximum height above its lowest foundation of 314 feet. Lake Merwin is about
14.5 miles long, with a surface area of approximately 4000 acres at full pool
level. Its maximum storage capacity is approximately 406,500 acre-feet, which is
equivalent to over 137 billion gallons. Its average annual generation is 517,812
Mwh, enough to power over 68,100 homes (based on an average household
electric use of 7600 kwh for Pacific states).
Merwin Dam and the adjacent powerhouse are on the National Register of
Historic Places. Both the dam and the powerhouse were built with Art Decostyle
architectural elements such as lamp-posts and building corners.
Yale Project
Construction of the Yale Project began in 1951, and continued until 1953. This
project includes two dams: a main embankment and an auxiliary “saddle” dam
that prevents spillover through a neighboring declivity.
Yale Dam and Yale Lake were named for the nearby town of Yale, which,
according to the Tacoma Public Library’s Washington Place Names database,
was given the name Yale over the second choice Spillel (or perhaps Spillei)
because of its brevity.
Unlike the Merwin Dam, the Yale dams are not concrete but constructed of
rock fill, with material taken from the site. The Yale Dam is a “rolled earthfill
embankment” type dam with a crest length of 1305 feet and a maximum height
of 323 feet above its lowest foundation. The Saddle Dam is approximately 1600
feet long and 40 feet high. Yale Lake is approximately 10.5 miles long, with a
surface area of approximately 3800 acres at full pool level. Its maximum storage
Sea Reach Ltd • 146 NE yamhill Street • Sheridan, OR draft 3 • November 2008 • page 68