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December 2007 Georgetown – Final Alternatives Analysis Report <br />page 7 <br />x 3 Assumes no special dewatering measures or reservoir lowering are needed to excavate for the pipe <br />placement. <br />x 4 Assumes six feet of reservoir lowering is required to excavate for the pipe placement. <br />Table 2: Comparative Analysis of Alternatives <br />1: Slide Gate 2: By-Pass through <br />dam <br />3: By-pass around <br />dam <br />Engineer’s Opinion of <br />Probable Cost $640,000 $750,000 3 <br />$1,080,000 4 $1,110,000 <br />Durability Excellent Excellent Excellent <br />Reliability <br />Excellent – with exposed <br />stems <br />Good – with submerged <br />operators <br />Good Good <br />Vulnerability Low Low Low <br />Ease of Operation and <br />Maintenance Good Good Good <br />Constructability <br />Poor <br />Difficult concrete removal; <br />Underwater construction <br />Poor <br />Difficult access; <br />Underwater construction; <br />Dam stability during <br />construction <br />Good <br />Potential utility conflicts; <br />Reservoir dredging; <br />Traditional construction <br />Timeliness of <br />Construction <br />Fair <br />SEO review required <br />Fair <br />Difficult access; <br />SEO review required <br />Good <br />No SEO review required <br />Opinion of Agency <br />Acceptability <br />High – with submerged <br />operators <br />Moderate – with exposed <br />stems <br />Moderate <br />Seepage potential <br />High <br />Regulation may not be <br />required <br />Provides potential to <br />remove Hydro siphon No Yes Yes <br />Need for a Dry Condition <br />During Construction <br />Required <br />Use of temporary bulkhead <br />Required for upstream <br />gate. <br />Also may need to lower <br />reservoir depending on <br />pore pressures. <br />Construction in a dry pit <br />with subsequent <br />excavation of the berm <br />between reservoir and <br />pit. <br />Spillway Blockage <br />Potential / Reduction in <br />Spillway Capacity <br />Low – with submerged <br />operators <br />High – with exposed <br />stems <br />None None