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Boy sen Dam Project
Will Harness the Big Horn in Wyoming
By JERRY LESTER '
B OYSEN dam, the first of the bureau of
reclamation-army engineers projects
in the 1947-48 program for Missouri river
basin developments is now well under way.
The $13,900,000 contract for construction of
this dam on the Big Horn river in Wy
oming was awarded to the Morrison Knud
sen Co., Boise, and work began last fall.
The contract calls for construction of the
main dam and hydroelectric power plant
and relocation of 14 miles of the Burlington
railroad. Work must be completed within
slightly more than four years.
The multiple purpose, earth filled dam
will be 218 feet high and 1,100 feet long at
the crest. It will back up the Big Horn river
18 miles south of Thermopolis, Wyo., into
a huge reservoir for hydroelectric power,
irrigation, silt and flood control. The 15,000
kilowatt power plant will have an annual
output of 68,000,000 kilowatt hours.
Boysen dam is not at all new to the Wind
River canyon. The original dam and the
new bureau of reclamation project are both
named after the man who designed and
built the first dam in 1910 as a private power
project. Most of the original dam structure
still remains where it was built, in the nar
rowest part of the 2,500 foot deep Wind Riv
er canyon (through which flows the Big
Horn river). A serious flood in 1923 caused
the railroad to be flooded out, and Boysen
was compelled to cut off the 50-foot super
structure that had been placed on top of the
original dam. Boysen continued to produce
power until 1925 with this lower dam, but
silt began piling around the power inlets
to his turbines and he was forced to aban
don the project,
Preliminary Work
Preliminary work at the dam has been
under way since May, 1946 when a contract
was let for construction of a power trans
mission line from the Pilot-Butte-Thermop
olis line to the Boysen unit and government
camp. Another contractor has been work
ing on the relocation of AVz miles of U. S.
highway No. 20 to skirt the site of the
proposed dam and lower end of the reser
voir. Two other contractors have been work
ing on warehouse buildings, offices and
residences at the government camp.
The Boysen dam reservoir will have a
capacity of 820,000 acre-feet at normal op
erating pool level, of which 260,000 acre
feet are below the lowest outlet and will
be available for silt control. The dam will
provide temporary additional reservoir
capacity of 673,000 acre-feet to assist in
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Turn to pages 14 and 15 for the
Montana Farmer • Stockman
Station, Daily Program Schedule
Meet the "Tankersley team" which
brings you the Pioneer league ball
games
KMON
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COVERS
AND
NORTHERN
WYO
passing major floods through the spillway,
New Lands Benefit
.
A total of 20,000 acres of new land will
be directly benefited by the reservoir. This
i s acreage of the Big Horn pumping
units of the Missouri basin project, located
in Washakie and Big Horn counties, Wy
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Penstock Tunr>el
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'BOYSEN 1>AM
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—Bureau of Reclamation Photos
This is fhe artist's conception of the upstream face of Boysen dam with very little water in the reser
voir. The crest of the coffer dam to turn the Big Horn river through the diversion tunnel at the left while
the main dam is under construction will also be the berm seen about one-third of the way up on the
face of the main dam. The 15,000 Kilowatt power plant is seen above the crest of the dam to the rear.
oming. Not only will the Boysen reservoir
supply the water for these units but the
power developed will drive the pumps that
will put that water on the land.
Another 80,000 acres of new land and
thousands of acres of land in existing proj
ects, all upstream from the reservoir, will
receive indirect benefits through the dam
and reservoir.
How can a dam aid in upstream irriga
tion? Through furnishing exchange water
for present irrigation systems, permitting
greater use of natural flows in the Wind
River basin. In other words, water from
this large reservoir can be used for down
stream irrigation without any curtailment
of upstream use on existing irrigation proj
ects.
T . ,
It will also be possible to construct neces
sary small dams for irrigation on land along
creeks which lead into the Big Horn river,
Construction of these dams without the
large Boysen reservoir would create a
shortage of irrigation water downstream,
p a rt of the new land to be benefited in
eludes units of the Missouri Basin project
known as the Fremont, Hudson Bench and
Shoshoni, all in Fremont county, Wyoming.
Flood, Silt Control
The operation of Boysen reservoir will
also control flood flows and greatly reduce
damage from floods originating above Wind
LEFT: The old Boysen dam is located IVi miles
downstream from the site of the new construction.
This dam was built by a private firm in the nar
rowest part of the wind River canyon and was
constructed primarily for power production. Flood
waters filled fhe reservoir to the extent that rail
road property was flooded. A SO-foot superstructure
was blown off the lop of the dam to reduce the
reservoir but this made power production impos
sible. At low right can be seen one of the silt
banks. Silt control is one of the principal purposes
for which the new project is being constructed.
River canyon. The reservoir will also re
move silt from the Big Horn river, thus
reducing maintenance costs of irrigation
works downstream. The silt capacity, 260,
000 acre-feet below the lowest outlet in the
dam, is considered large enough to handle
all the river silt for over 100 years.
The seriousness of the silt problem is
indicated in the checks made at Worland
showing that 4,000 acre feet of silt comes
(Please turn to page 2)