C150297 Approval Letter - Laserfiche WebLink

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Farmers Reservoir and Irrigation Company July 14, 2009 (UPDATED July 22, 2009) Page 5 of 8 TABLE 1 PROJECT COST- MILTON RESERVOIR OUTLET WORKS Construction $ 591,000 Testin $ 11,000 Contingency $ 56,000 Construction Mana ement $ 40,000 TOTAL $ 698,000 B. Milton Reservoir Spillway Agenda Item ] 0 The SEO has indicated that the existing spillway at Milton Lake is not adequate to safely pass the design storm event and has directed the Company to design and constxuct a larger spillway to meet State standards. Alternative No. 1- No Action: This alternative was considered unacceptable because by not increasing the capacity of the spillway, the Company would be ignoring the requirements of the SEO and Milton Reservoir would likely be put under a fill restriction. Alternative No. 2(SELECTED) - Enlarge the Spillway with a Concrete Control Structure and Earthen Channels Upstream and Downstream from the Spillway Crest: This alternative involves enlarging the existing spillway. This alternative would meet the Company's objective of improving the spillway to safely pass the design storm event as dictated by the SEO; thereby allowing the Company to continue to operate Milton Reservoir to its full decreed amount without the concern of the dam overtopping. The estimated cost for this alternative was $984,000. Alternative No. 3- Enlarge the Spillway with a Concrete Control Structure and Concrete Channels Upstream and Downstream from the Spillway Crest: This alternative involved modifying the existing spillway by expanding it just as in Alternative No. 2. In addition, 400 feet of channel downstream of the spillway crest would be armored with a concrete lining to prevent erosion downstream from the spillway crest section. This would eliminate spillway maintenance if an event was to occur. The estimated cost of this alternative was nearly $3,900,000. The Company selected Alternative No. 2 because it meets its objectives of continued safe operations of the dam, it complies with the SEO's directive that the spillway be enlarged, and it will allow the Company to continue to store its maximum decreed water volume, all in a cost effective manner. This portion of the Project involves widening the spillway from 350 feet to 586 feet and lowering the elevation of the spillway by 1.5 feet. Areas upstream and downstream of the spillway will be graded to provide an efficient flow path from the reservoir through the spillway and on downstream of the dam. Appropriate hydraulic cutoff walls will be added downstream from the spillway to prevent erosion during the design storm event.