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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Feasibility Report for Dam Safety Modifications to DeWeese Dam <br />April 22, 1997 <br /> <br />11 <br /> <br />Removal of the existing crest section effectively eliminates the problem of the weathering and <br />deterioration of the existing concrete placed after construction of the original dam. In addition, <br />with good bonding of the new concrete to the original dam concrete and a properly functioning <br />drainage/seepage control system, the replacement crest section will provide adequate factors of <br />safety under all loading conditions evaluated, and will meet SEO requirements. <br /> <br />Conceptual design details of Alternative No, I are shown on Figure 5 and include the following <br />components: <br /> <br />Demolition <br /> <br />Complete demolition and removal of the existing crest raise sections would be the first step in <br />construction of Alternative No, 1, The method assumed for this study consists of a two-step <br />process: <br /> <br />. Demolition and removal of approximately the top II feet of the crest raise <br />sections by cutting the concrete into reasonably sized blocks using a diamond <br />wire saw, <br /> <br />. Demolition and removal of the remaining 1 foot of the crest raise sections using <br />conventional hand methods such as jack hammering, <br /> <br />As an alternative demolition method, controlled blasting could be used to remove the existing <br />crest section. The use of blasting for concrete demolition would require a carefully developed <br />and written technical specification, with very strict controls and monitoring requirements, along <br />with carefully developed qualification requirements for the blasting subcontractor. The fmancial <br />benefits of controlled blasting could amount to as much as a 50 percent reduction in the project <br />demolition costs presented for this alternative. Demolition by controlled blasting has been <br />completed successfully on other projects involving modifications to concrete dams, <br /> <br />Detailed evaluation and selection of the preferred demolition method for Alternative No, 1 will <br />be made during final design. <br /> <br />Disposal of the demolished crest concrete is an issue that will also need to be addressed during <br />the final design phase of the project. Our estimates for this study indicate that about 1600 cubic <br />yards of demolished concrete will have to be disposed of for this alternative. Two options <br />available for disposal of the demolished concrete are: I) disposal of the concrete in the reservoir, <br />or 2) disposal of the concrete off-site, While disposal of the crest concrete in the reservoir would <br />be less costly, care would need to be taken to ensure that the discarded concrete does not <br />interfere with the operation of the outlet works or with recreational boating during times of low <br /> <br />96006\REPQRTS\FEAS\TEXT.NEW <br /> <br />!t! GEl Consultants, lnc, <br />