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Supply Irrigating Ditch Co. Agenda Item 11b. <br />January 24-25,2001. <br />Water Riqhts <br />The water rights owned by the SIDC include a direct flow right in amount of 92.2 CFS from St. <br />,� Vrain Creek, and a 51 % interest in the Beaver Park Reservoir. The Beaver park interest <br />delivers approximately 800 acre-feet per year. Records of the State Engineer's Office (1997 — <br />1999) indicate that �he average annual volume diverted by the Supply Ditch has been about <br />9,500 acre-feet. <br />Proiect Description <br />During the study of Knoth Reservoir and Dam, the following alternatives were evaluated: <br />No action alternative <br />1) Complete rehabilitation of the two dams to Gage Height 20 feet ($590,200) <br />2) Complete rehabilitation of the two dams to Gage Height 25 feet ($1,233,700) <br />3) Complete rehabilitation of the two dams to Gage Height 30 feet ($1,898,000) <br />Following is a summary of each alternative: <br />No Action Alternative. <br />This alternative was rejected because the need is apparent for some storage within the system to <br />increase the usable yield and to allow for more efficient operation of the ditch <br />Alternative 1- Rehabilitate the dam to its current capacity (Gage Height 20 feet) <br />This alternative involves rehabilitation of the dam to approximately its current height and size <br />which will store approximately 220 acre-feet. The total project cost is $590,200. This alternative <br />� would not allow storage of the full conditional decree, and was rejected for that reason. <br />Alternative 2- Raise Dam Crest To Gage Height 25 feet. <br />This alternative is similar to Alternative 1 in all respects except the crest of the dam will be <br />raised approximately five feet in elevation from gage height 20 feet to gage height 25 feet. This <br />increases the reservoir storage to approximately 360 acre-feet. The total project cost is <br />$1,233,700. This alternative would not allow storage of the full conditional decree, and was <br />rejected for that reason. <br />Alternative 3- Raise Dam Crest To Gage Height 30 feet. <br />Thus alternative is similar to Alternatives 1 and 2 in all respects except the crest of the dam will <br />be raised approximately ten feet in elevation from gage height 20 feet to gage height 30 feet. <br />This increases the reservoir storage to approximately 540 acre-feet. The total project cost is <br />$1,898,000. This alternative would allow storage of the full conditional decree, and is the <br />preferred alternative. <br />Selected Alternative 3 involves <br />l. Reshaping the upstream face of both dams and placement of a compacted clay <br />liner over the upstream face to inhibit seepage. <br />� 2. Excavation of a cutoff trench tied into the clay liner indicated above. <br />3. Installation of a toe drain along the north dam . <br />4. Construction of a 200 foot spillway at the right abutment of the south dam <br />2 <br />