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No Action: Due to current deterioration of the existing diversion wall, it is now inadequate: to protect the highway, pools and adjacent public facilities against damag,e due to flows overtopping or breaking through of the wall. Risk of overtopping and/or failure in a major storm event is considered high. Failure ofthe existing wall increases the hazard to the pools as not only would the natural flows and debris be deposited in and around the pool facility but also the wall material (rocks, timber, fencing and miscellaneous construction materials) would be added to the flow. No report of personal injury was made following past facility damage due to Skyrocket Creek flows, but a risk for injury or loss of life exists if advance warning of the flood event and wall failure is not available. The No Action alternative is not a viable plan due to risk to life and property. Reconstruction of Diversion Wall Sub-alternatives were considered in conceptual design of the wall reconstruction that included: a) rock-filled steel crib wall b) reinforced concrete wall c) gabion wall d) stone and masonry gravity wall e) concrete wall with tensioned anchors. Buckhorn Geotech developed the first three of these sub-alternatives in 1990 fur the City of Ouray. The walls were to span approximately 35-feet with a height of approximately 12-feet to tie into adjacent bedrock at each end of the diversion wall. The recommended alternative was the rock-filled steel crib wall due to on-site availability of rock material and durability of construction. Preliminary construction costs were updated December 2000 to give a total of$67,600. Adding a IS-percent factor for engineering and a 15- percent contingency gives total estimated costs of$87,880. The stone and masonry gravity wall alternative was developed by Ayres Associates for the U.S. Army Corps of Engineers (under subcontract with JOllies and Stokes and Associates) in 1997. This wall was proposed to span approximately 30- feet and be a maximum height of 10-feet to contain the estimated 100-year debris flow. The report notes that the one reason for selection of this type of construction over the previous recommendations was to utilize on-site rocks, limiting the need to haul construction materials to the remote site. Preliminary construction costs were estimated at approximately $ 50,000 at that time. Using a 5% inflation per year gives an estimate of construction costs in 2001 of$60,775. Adding a IS-percent factor for engine(:ring and a IS-percent contingency gives total costs of $79,008. The alternative for construction of a concrete wall with tension,ed anchors, was developed by the U.S. Army Corps of Engineers (USACE), Sacramento Office, for City of Ouray in 2000. Preliminary construction costs were estimated at approximately $ 300,000. This wall is approximately 35-feet in length with maximwn height of 10-feet. 7