CT2015-026 Approval Letter - Laserfiche WebLink

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Riverside Reservoir and Land Company May 12, 2009 (UPDATED May 22, 2009) Page 4 of 6 Agenda Item 17g Alternative No. 1 was considered unacceptable due to the fact that the SEO has imposed a storage restriction and the Company is concerned that the restriction will be progressively increased to reduce the available storage. Selected Alternative No. 2 was selected because of the location near the east end of the embankment where the dam height is low and the dam crest ties into a natural intermediate abutment. This location will allow for the spillway structure to be constructed on a natural foundation and not on the dam embankment. Alternative No. 3 was ruled out because these alternate spillway locations were both in areas that are prone to severe wave action due to the prevailing winds from the north. This wave action could cause a significant amount of dynamic loading and spilled water; therefore, the locations were not as ideal as the chosen location. The Company selected Alternative 2, a concrete spillway structure at Station 57+OOE. The spillway will consist of an ogee crest weir, a 30-foot wide open channel concrete chute, a 40-foot wide dissipator, and a transition section from dissipator to an excavated outfall channel. In addition, a bridge or multiple series of culverts will be installed across the spillway for the county road access to allow for safe passage of the regulatory flood (100-year) without damage to the road. The selected site provides the simplest construction, the longest construction time window, the safest construction due to the low dam height and wide abutment area for construction, minimized potential for wave induced incidental spill, and the safest operation due to limited normal wave impact. There are a few permitting items that will need to be addressed with the construction of the Project. Spillway easement leases across Equus Farms and the State of Colorado properties are necessary. A spillway flood easement has been obtained from Equus Farms. Lease discussions are under way with the State of Colorado. In addition, a permit for a County road crossing will be required by Weld County to bridge County Road 89 by the spillway chute. The following schedule has been proposed: final design complete by January 2010, SEO approval by May 2010, construction beginning in July 2010, and the Proj ect being complete and operational by March 2011. (Note: The inflow design flood has been approved by the SEO.) The engineer's estimate of probable construction costs is presented in Table 2.