Dams and Impounded Rivers - River Dynamics and Integrated River Management - page 430

A few large dams have been and will be removed due to various reasons. On the White Salmon River
in Washington State, the 38-m high Condit Dam is required to add modern fish ladders to mitigate its
negative impacts on the eco-system. The fish ladders and other improvements would have cost more than
$30 million. Dam removal is a better choice because the cost of dam removal is only $15 million.
The 32-m high Elwha Dam and 82-m high Glines Canyon Dam on the Elwha River were built in the
early 1900s to power timber mills in the nearby town of Port Angeles, Washington State, as shown in Fig.
7.30 (http://www.irn.org/revival/decom/brochure/rrpt2.html). They are the highest dams ever slated for
removal at government expense. The private dams, now within the Olympic Peninsula National Park,
destroyed magnificent local runs of Pacific salmon, diminishing an important cultural symbol. Extinction
of Elwha River sockeye salmon, and drastic declines in the river's ten other native species, undermines
fishing rights of the Lower Elwha Klallam, a federally recognized Indian Nation. In 1992, the government
finally heeded tribal demands to provide "full restoration" of the Elwha River, including dam removal. After
25 years of campaigning by the Lower Elwha Klallam Nation and conservation organizations, Congress
approved funds in 1999 to purchase the dams. Once acquired, the government will begin dam removal
activities estimated to cost at least $100 million. Restoration of the Elwha represents the last, best hope
for resolution of Lower Klallam fishing rights and the return of a once spectacular salmon river.
(a) (b)
Fig. 7.30 The 32-m high Elwha Dam (a) and 82-m high Glines Canyon Dam (b) on the Elwha River, Washington,
U.S. are going to be removed
Removal activities will start in 2008. Deconstruction of the Elwha Dam will be the most complex part
of the three year project and will be undertaken in 6 phases, as shown in Fig. 7.31:
Phase 1 Open the four spill way gates on the south side of the dam to lower the level of the Lake
Aldwell Reservoir 5.5 m in one month;
Phase 2 Remove the south gates and dig a diversion channel. Blast a 9.14 × 10.67 m plug of bed rock
in five stages and reroute the river through the gap in 3 months;
Phase 3 Take out the north spillway and upper portion of the dam and install a 3.7 m wide road in
order to access the penstock tubes in one month;
Phase 4 Remove steel penstocks and slide gates, the concrete intake structure and power house in 5
months;
Phase 5 Haul out 152,900 m 3 of rock, earth, concrete, and fir trees that were placed behind the gravity
dam after a 1913 burst in a month.