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I I I I I I I I I I I I I I I I I I I Feasibility Report for Dam Safety Modifications to DeWeese Dam April 22, 1997 13 Reinforcing bar dowels should be drilled and grouted into the original dam section as a second line of defense for sliding stability of the dam. The new crest section most likely would be placed in one full-height lift using conventional, air- entrained concrete, For construction and thermal cracking considerations, the new crest section is expected to be constructed in 20- to 40-foot-long blocks, All vertical construction joints would be keyed and include a conventional PVC waterstop, Concrete mix design requirements would be included to provide durable concrete with minimal potential for thermal cracking. Handrails Handrails should be included on both the upstream and downstream sides of the crest to improve crest access safety at the dam. 3.4 ALTERNATWE NO.2 - CREST REHABILITATION Alternative No, 2 consists of removing all unsound concrete from the existing crest section, installation of passive anchors, and construction of a new concrete cap section, The amount of concrete that must be removed from the exterior surfaces of the existing crest section is not known and would have to be a field engineering decision. The new cap section would be constructed to match the geometry of the existing crest raise sections, A drainage/seepage control system would be installed within the cap concrete, and would be similar to that for Alternative No,l, If performed correctly, removal of the deteriorated concrete from the existing crest section will address the dam safety issues regarding deterioration of the existing concrete, The rehabilitated crest section would provide adequate factors of safety under all expected loading conditions, assuming installation of the passive reinforcement anchors in conjunction with a properly functioning drainage/seepage control system, Stability requirements of the SEO would be fully met by Alternative No 2. Details of the proposed crest rehabilitation alternative are shown on Figure 6 and include the following components: Demolition Demolition and removal of all of the unsound concrete from both faces and the top surface of the existing crest raise sections would be the first step in construction of Alternative No.2. Techniques for removal of the unsound concrete for this rehabilitation alternative would be quite different from those used for the replacement alternative and would be expected to be very labor 96006\REPORTS\FEAS\TEXT.NEW ~ GEl Consultants, Inc.