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<br />Feasibility Study
<br />Mariano (Boedecker) Reservoir Dam Rehabilitation
<br />September 200 I
<br />
<br />Selected Alternative
<br />
<br />The selected project consists of a rehabilitation which includes construction of a toe drain, toe berm,
<br />outlet modifications, foundation grouting, and other ancillary items, Feasibility level layout and design is
<br />attached in Appendix C.
<br />
<br />The project will begin with the modifications to the outlet works, Outlet works improvements will
<br />include lining of the existing masonry arch tunnel with a circular conduit and grouting of the annular
<br />space between the new conduit and the old arch tunnel. The existing upstream gates will be replaced with
<br />new slide gates. The outlet pipe will be extended downstream approximately 30 feet to allow room for
<br />toe berm construction.
<br />
<br />As shown on the proposed dam cross-section drawing in Appendix C, a granular toe drain blanket and
<br />perforated pipeline will be constructed along the toe of the existing dam, A toe berm will also be
<br />constructed along the toe ofthe dam above the toe drain to provide protection from deep seated slope
<br />instabilities, This toe berm will be approximately 20 feet wide and on~third the height ofthe dam, The
<br />downstream slope of the dam above the proposed toe berm will be flattened, from a 2:1 (horizontal to
<br />vertical) slope to a 2,5:1 slope to reduce the occurrence of shallow slides on the face of the dam, The
<br />construction budget also includes a cost to re-establish wetlands if required by the V,S, Corps of
<br />Engineers, This wetlands mitigation may be needed to replace existing cattail-type vegetation supported
<br />by seepage through the dam, A cost is also included to relocate two City of Loveland electric
<br />transmission line structures, These wooden towers are located near the downstream toe of the dam and in
<br />the crest of the dam, Relocation of the towers will help facilitate construction and improve dam safety.
<br />
<br />Cost Estimate
<br />
<br />The estimated cost of the project is $1,048,000, Table 2 provided a detailed Engineer's Opinion of Costs
<br />by item,
<br />
<br /> Table 2
<br /> Mariano Dam Rehabilitation
<br /> Engineer's Opinion of Cost
<br />Item No. Description Unit Quantity Unit Cost Extension
<br />I Mobilization LS 1 $37,500 $37,500
<br />2 Clearing and Grubbing Acre 2 $1,500 $3,000
<br />3 Slope and Foundation Preparation LS 1 $40,000 $40,000
<br />4 Bedrock Grouting Along Dam Crest LS 1 $100,000 $100,000
<br />Alignment
<br />5 Improvements (borrow excavation, CY 12,000 $10 $120,000
<br />haul, fill, placement)
<br />6 Topsoil and Revegetation (2 acres) LS 1 $20,000 $20,000
<br />7 Existing Outlet Slip Liner LF 120 $250 $30,000
<br />8 Head Gate Vault Modifications LS 1 $20,000 $20,000
<br />9 New 48" Head Gate EA I $30,000 $30,000
<br />10 Downstream Outlet Extension Pipe LF 30 $280 $8,400
<br />11 Toe Wall LS 1 $20,000 $20,000
<br />12 Grouted Riprap CY 30 $80 $2,400
<br />13 Blanket LF 1,200 $90 $ 1 08,000
<br />14 Wetland Mitigation Acre 1 $70,000 $70,000
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