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Oligarchy Irrigation Company Agenda Item 11a July 15-16, 2015 Board Meeting(Updated July 17, 2015) Page 3 of 5 Water Rights Oligarchy Reservoir No. 1 has the following decreed water rights: TABLE 1: STORAGE WATER RIGHTS Appropriation Adjudication Name Amount (AF) Date Date Original 1080 7/2/1889 3/22/1890 First Enlargement 357.4 3/31/1890 3/13/1907 Second Enlargement 386 11/14/1892 3/13/1907 Third Enlargement 306 11/1/1911 6/1/1926 Partial Refill 272 12/31/1929 7/23/1951 Refill 1858 12/31/1929 7/23/1951 According to State of Colorado Division of Water resources records, Oligarchy Reservoir No. 1 has provided an average of 795 acre-feet per year to the Oligarchy Ditch for irrigation use. Project Description Five alternatives were considered for this project: Alternative No. 1 - No-action was considered unacceptable, as the SEO 2014 Engineer's Inspection Report requested that the outlet works pipe be unpressurized and provide access to inspect the entirety of the outlet works system. The dam is considered a significant hazard dam by the SEO. If the outlet works fails in the future, significant costs from damages to private and public buildings and infrastructure in the vicinity of the Town of Hygiene would likely result. A future storage restriction by the SEO would also be a possibility in the future. Alternative No. 2 - Install new hydraulic gate system and reconstruct concrete intake structure The new hydraulic gate would be hydraulically operated from a concrete vault on the dam crest. The advantage to this alternative is minimum disturbance to the existing dam; disadvantages include continued existence of a pressurized pipe under the dam, continued deterioration of the existing outlet works pipe through the dam, and the need to completely drain the reservoir for any inspection. Cost: $830k Alternative No. 3 - Bridge, gate, and reconstruct concrete intake structure A bridge, approximately 80 feet long, would be built out to a new concrete intake structure so that the operator could be mounted directly above on the bridge. The primary advantage of this alternative is the simplicity of a sluice gate system; disadvantages include susceptibility to ice loading damages, continued existence of a pressurized pipe under the dam, continued deterioration of the existing outlet works pipe through the dam, and the need to completely drain the reservoir for any inspection. Cost: $870k Alternative No. 4 - Slope stem gate - this system would involve reconstruction and steepening of the upstream dam embankment slope to construct a new gate and stem supported by a new concrete structure. Partial removal of the outlet pipe would be required so that the concrete structure could be connected to existing outlet works system. Advantages of this alternative include elimination of the pressurized pipe, continued deterioration of the existing outlet works pipe through the dam, and the need to completely drain the reservoir for any inspection. Cost: $871k Selected Alternative No. 5- New outlet works gate vault, outlet works piping, intake, and discharge structures is the selected alternative because it remedies all of the SEO requests about the outlet works system. This alternative provides for replacing the whole outlet works system with new intake and discharge structures, and a gate vault located on the upstream side of the dam for a service spillway. Existing cast iron piping will be replaced with PVC joint-restrained pipe encased in concrete