PROJ00345

• Contract/PO #: C153330
• Contractor Name: Upper Yampa Water Conservancy District
• Contract Type: Loan
• Water District: 0
• County: Routt
• Bill Number: SB 77-35
• Loan Projects - Doc Type: Feasibility Study

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Specification
Page or Draw-
ing No.

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Dwg. 2

The pipe drainage system under the downstream shell is under-

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stood to be less expensive than a system composed entirely of

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gravel. This would appear reasonable if gravel must be im-

ported from an established source many miles away. If the

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contractor should elect to set up a crusher near the site, how-

ever, a large part of the total cost would be in the fixed

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expense of plant set-up and removal. Under these circumstances

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the cost of additional material would be relatively low as only

additional operating and haul costs would be involved. The

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cost savings realized by use of pipe thus appears to depend

upon the gravel source which may not be known until construction

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starts. From a design standpoint, the longitudinal collection

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pipes under the central part of the dam appear to be unnecessary

if the chimney (gravel filter) drains the downstream shell

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properly. The gravel filter material surrounding these collec-

tor pipes could be more effective if placed as a thicker zone

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surrounding the header pipes. It is recommended that a final

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review be made of the economics of eliminating th~ pipe system

completely or that an all-gravel system be included as an

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alternative. If the pipe system is retained, it is recommended

that telescoping slip joints be provided in each straight run

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of pipe. These joints can be made simply by placing a sleeve

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of larger pipe over the butt joint. This device has been

used in at least one recent dam to avoid tension failure as

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deformation of the dam occurs,

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