News letter Dam edition

Ingeokring Newsletter
Hungry Horse Dam
On the road from Kalispell to Glacier National Park, I stopped
along the road for a view of the Hungry Horse Dam. This
dam is a concrete thick arch dam, located in a narrow canyon
in the Flathead River, near Columbia Falls in Montana.
Construction started in 1948 and at the time of its completion
in 1953, the dam was the third largest dam, and the
second highest concrete dam, in the world. Currently, it is
the largest dam in Montana and nr. 11 in the list of largest
concrete dams in the USA.
situated in the Columbia River near the towns of Grand Coulee
and Electric City. The dam is part of Lake Roosevelt National
Recreation Area, administered by the National Park
Service. The dam itself is operated by the U.S. Bureau of Reclamation.
Grand Coulee Dam, with its three powerhouses, forms the
largest hydro-electric project in the USA and the fourth largest
in the world. It is the largest concrete structure in the
USA, with 9.16 million m 3 of concrete used. Crest length of
the dam is 1 592 m, while its height is 168 m. Base width is
152 m and crest width is 9 m.
Construction of the original project started in December
1933, as part of the Columbia Basin Project for irrigation of
desert areas of the Pacific Northwest and for the production
of electricity for the then rapidly expanding cities of Spokane,
Portland, Seattle and Tacoma. Foundation rocks at the
dam site consist of hard, sound, massive granite varying
from coarse-grained in the right abutment to fine-grained
porphyritic in the left abutment.
Fig. 7 View on Hungry Horse Dam from the road between Columbia
Falls and Glacier National Park (source: author’s photo).
The 172 m high dam is a variable-thickness concrete arch
structure with a crest length of 645 m. Crest width is 10 m,
base width 98 m. The dam and appurtenant works contain
2.4 million m 3 of concrete. The spillway is the highest morning-glory
structure in the world. Water cascading over the
spillway rim drops a maximum distance of 149 m. The capacity
of the spillway is 1 415 m 3 per second, and the reservoir
has a total surface area of 96 km 2 .
Construction finished in 1942, and numerous modifications
followed in more recent years. The first power was generated
in 1941 and the last of the original 18 units (of the initial
two powerhouses, one at each side of the dam’s spillway)
started production in 1950. Between 1966 and 1974
the dam was expanded to add the Third Powerhouse. The
original dam was modified for the Third Powerhouse by a
357 m long, 61 m high forebay dam along the right abutment
approximately parallel to the river and at an angle of
64 degrees to the axis of Grand Coulee Dam. This involved
demolishing 80 m of the northeast side of the dam. The
addition accommodates six new generators. These new
turbines and generators, three 600 MW and three 805 MW
The dam is used for power generation, using 71 MW generators.
The generator capacity was upgraded in the 1990´s to
107 MW each, for a total plant capacity of 428 MW. The
dam’s foundation consists of Siyeh Limestone in regular
beds ranging from a few centimetres to metres thick, made
highly insoluble by impurities. Cut by one major and several
minor shear zones, and one major bedding-plane slip.
Grand Coulee Dam
After Hungry Horse Dam, I travelled through Canada for two
weeks and after that I went south again and visited the
beautiful northeastern part of the state of Washington. After
crossing the border between the USA and Canada, I went to
the giant Grand Coulee Dam. This is a concrete gravity dam,
Fig. 8 Grand Coulee Dam, with Right and Left Powerplants at both
sides of the spillway and Third Powerhouse and Forebay Dam at the left
side (source: U.S. Bureau of Reclamation).
Dam edition | Double Issue 2007/2008 | 56