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3. Enlargement of the current spillway and increase the dam freeboard with a parapet wall. <br />4. Enlargement of the current spillway and increase the dam freeboard with soil. <br />5. Enlargement of the cuITent spillway, increase the dam height to increase freeboard and <br />create additional storage. <br />Alternative No. 1 was considered ~nacceptable since it means the North Sterling Resenroir <br />storage would be restricted by the SEO. <br />Alternative No. Z was ruled out because enlarging the spillway alone would req~ire a <br />substantial amount of earthmoving without addressing the dam crest. <br />A/temative No. 3 was ruled out due to the cost of construction of the parapet watl. <br />Altemative No. 4 was selected because with additional freeboard the width of the spitlway is <br />significantly less fherefore requiring significanfly less earthmoving and at the same time <br />addresses the dam crest issue. <br />Alternative No. 5 was ruled out predominately due to cosf but also due the inabiiity to attracf <br />partners in the increased storage. <br />The Selected Alternative <br />The selected altemative, Alternative No. 4, consists of widening of the current au~aliary spiNway <br />from 530 feet to 915 feet, lowering the crest of the auxiliary spillway by 0.5 feet (to match the <br />primary spillway), and raising the dam crest with earth. Also included in the project is the <br />construction of seepage collection system on the downstream slope of the dam. <br />W.W. Wheeler and Associates, Inc. (Wheeler) perFormed the design of the spillway and the <br />design has been reviewed by the SEO. On December 30, 2008 the SEO sent a list of 26 <br />questions to be addressed priar to approval of the design. Currently Wheeler is making the <br />necessary changes to the design documents to address the SEO requests. It is expected that <br />the cuRent design will receive approval in the very near future. The Dec~ember 30, 2008 letter <br />can be found in Appendix D. The design is attached to this feasibility study. The North Sterling <br />Irrigation District has been provided a detailed cost estimate from Comerstone Construction of <br />Sterling, Colorado, which is presented in Table 1. <br />North Sterling Irrigation District Page 9 of 13 <br />Dam Crest and Spillway Improvement Feasibility Study <br />March 1, 2009 <br />