WSP00568

• File Number: 8441.100
• Description: Colorado Big Thompson
• Basin: South Platte
• Date: 1/1/1947
• Author: unkjnown
• Title: What Colorado's Mountain Waters Mean to the State and the Nation
• Water Supply Pro - Doc Type: Report/Study

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diverted for production of food. S. S. Magoffin, Inc., of Englewood,
COlorado, contracto~ for the eastern half, completed that portion on
February 15, 1946. Stiers Brothers Construction Company of St. Louis,
Missouri, completed the western half shortly afterwards.

Green Mountain Dam

In order to protect the water users in the Colorado River Basin
against depletion of their water supply by diversions through the Alva B.
Adams Tunnel and to assist in further development of western slope irri-
gation,andGreen Mountain Reservoir has been constructed on the Blue River.

The dam is an earth and rockfill embankment type with a maximum height
of 274 feet above stream bed and crest length of about 1,100 feet. It has
a top width of 40 feet, a J to 1 upstream slope and a 2t to 1 downstream
slope. There are 3,072,000 cubic yards of cl~, sand and gravel, rolled
in 6-inch layers, in the embankment and 1,245,000 cubic yards of cobble
and rock fill and riprap on the slopes. . It is one of the highest and.lar-
gest earth and rockfill dams which have been built in this count~.

The reservoir floods 2,100 acres of land and has a capacity of 154,650
acre-feet total storage. The irrigation outlet capacity is 1,000 second-
feet .nth the reservoir water surface at elevation 1,812. The spillway
discharge capacity is 25,000 second-feet with the reservoir water surface
at elevation 7,950.

On November 12, 1938, the Warner Construction Company of Chicago,
Illinois, was awarded the contract for building the Green Mountain dam
and power plant. Construction of the dam was completed in June 1943, ex-
cept for the spillway gates which were installed in 1945.

This reservoir has provGln to be a ve~ popular recreation feature for
boating and fiShing.

Shadow Mountain Dam

Construction of the Shadow fuountain Dam and Dikes on the western slope
is completed. The dam and dikes are of the earth and rockfill type. The
dam is 63 feet high from the lowest point of the excavated foundation to
the top and has a combined crest length of 3,100 feet. Shadow Mountain
Reservoir formed by this dam will add 1,356 acres to the surface area of
Grand Lake and, with an allowable water surface fluctuation of one foot,
will provide a small amount of storage for correlating the Granby pumping
plant discharge with the intlovt to the Alva B. Adams Tunnel.

Because of the stable water level and relatively shallow depth, the
lake should have a gr6at recreational value. Boating and fishing should,
be excellent. At the present time, a recreation plan is being prepared
for the area that will guarantee its greatest possible use by the public.

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