WSP00377

• File Number: 8220.128.A
• Description: Silt Project
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 10/1/1945
• Author: USDOI - BOR
• Title: Silt Project-Colorado ‎(Draft of Project Planning Report)‎ Part 2 of 2
• Water Supply Pro - Doc Type: Report/Study

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The dam would be clay, sand and gravel rolled fill with maximum

height of 127 feet and a crest length of 800 feet. The compacted clay,
sand and gravel section is bound on the upstream face by 3 feet of
riprap from the crest elevation of 5954 down to a 20 foot berm at

elevation 5875. The slope from the berm is brought down on a 5 to 1

scale to the ground surface. The downstream face of the dam will have

a rock filled cover with a slope of 2 to 1 from the crest elevation

of 5954 to 5855 where the slope will be 5 to 1 down to elevation 5830

and then 2 to 1 to the ground surface. The downstream face of the

compacted earthfill (upstream face of rock fill section) is placed on

a slope of 1.9 to 1 beginning 5 feet in from the downstream edge of the
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crest. The main fill :b composed of an impervious center section

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with a semi-pervious cover beneath the riprap and rock filled slope.

The coffer dam wpich will become an integral part of the dam is composed

of materials stripped from the foundation.

Four shallow cut-off trenches located upstream and parallel to the

dam axis across the canyon floor will be brought in obliquely toward

the crest on the abutments. The first cut-off trench is located 25

"

feet upstream from the axis with the remaining 3 at successive intervals _.'
of 50 feet. The trenches will have a trapazoidal section, 10 feet
bottom width, and an approximate depth of 6 feet.

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Two feet of stripping Qver the entire area of the dam foundation
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is believed sufficient to provide a surface of good ~ between the

foundation and the embankments. Eight and ten inch sewer pipe drains

embedded in gravel will be placed beneath the rock filled section along

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