PROJ00454

• Contract/PO #: C153832
• Contractor Name: DeWeese-Dye Ditch and Reservoir Company
• Contract Type: Loan
• Water District: 12
• County: Custer
• Bill Number: HB 98-1189
• Loan Projects - Doc Type: Feasibility Study

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Feasibility Report for Dam Safety Modifications to DeWeese Dam
April 22, 1997

15

during final design of the project), As part of the drainage system, these outlets would provide
exit paths for the water collected in the PVC quarter section drains and would allow routine
cleaning and maintenance access for the dr~inage system. Horizontal drilling through the
existing concrete could be performed from temporary scaffolding attached to the upstream
3-foot-wide ledge created by the original dam crest. The outlet holes would be sloped for
positive drainage to reduce the possibility of standing water in the hole, which could freeze and
continue deterioration of the existing concrete, Connection of the PVC drain pipe to the drilled
outlet holes would be accomplished using 3-inch-diameter half section PVC pipe teed off of the
quarter-section pipe, These collection pipes would be placed directly against the upstream face
of the remaining existing concrete face,

Passive Anchors

The passive reinforcement anchors would consist of #14 epoxy-coated reinforcing bars at 3,5'
spacing along the entire crest length,

These passive anchors will transfer shear and tension forces from the rehabilitated crest raise
sections to the original dam section under all expected loading conditions,

Instaliution of these passive anchors would involve drilling 4-inch-diameter holes through the
remaining existing crest concrete and 10 feet further into the original dam concrete, The anchor
bar would then be placed in the hole and grouted in-place, Placement of the structural "cap"
concrete would follow anchor installation.

Concrete Cap

Successful repair of existing concrete results from the correct choice of method and the
establishment of acceptable performance teclmiques [8]. Key requirements for a successful
concrete restoration project include the following:

. Careful preparation of the receiving surface
. Careful construction and setting of the form work
. Careful concrete mix design
. Thorough vibration of the freshly placed concrete

In order to meet these requirements, a tightly controlled technical specification would need to
be prepared during fmal design, Although thennal cracking is not likely to be a problem in this
application, the use of temperature and shrinkage reinforcement, in the form of steel wire mesh,
for the cap concrete is recommended,

96006\REPORTS\FEAS\TEXT.NEW

~ GEL Consultants, [nc,