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<br />-7 - <br /> <br />. <br /> <br />The owners of North Sterling Dam have been considering a variety of modifications to the <br />dam to allow increased storage and IDF routing capability. These options include a 2 ft and 8 <br />ft increase in the dam. The evaluations of these options have indicated that a 2 ft raise would <br />result in a spillway reduction of an additional 400 ft., an increase of 8 ft could result in no <br />increase in the existing spillway due to improved routing capability of the IDF. The State <br />Engineer continues to work closely with the North Sterling Irrigation District and the <br />Districts engineer in meeting the Districts goals and protection of the public. <br /> <br />Red Mesa Ward Reservoir <br /> <br />Red Mesa Ward Dam, near Red Mesa Colorado is currently a Significant Hazard dam. <br />Development downstream of the dam is likely to result in the dam being classified as a High <br />Hazard dam in the future. The dam owners, La Plata Water Conservancy District, completed <br />a Hydrology Study in September 2002 as part ofthe evaluation by the La Plata Water <br />Conservancy District to enlarge the capacity of the reservoir and dam to increase storage <br />capacity by increasing the height ofthe dam by 29 ft. The estimated cost of the 29 ft dam <br />embankment raise, outlet replacement and spilIway is $7.1 million, the spillway is estimated <br />at $1.6 million, 22% ofthe total cost. <br /> <br />. <br /> <br />The District's engineers determined that upon review of the development downstream of the <br />dam it was likely the hazard classification would change to a High Hazard dam regardless of <br />whether the enlargement proceeded. As a High Hazard dam, the spillway and reservoir <br />system is required to have the capacity to safely store and pass the IDF generated by the <br />probable maximum precipitation (PMP) rainstorm event without overtopping the dam. The <br />State Engineer reviewed and approved the hydrology study prepared by the District's <br />engineers in 2003. This investigation was performed to determine the approximate <br />magnitude of the inflow design flood (IDF), reservoir routing eapability and preliminary <br />design of the emergency spillway. <br /> <br />In response to questions posed by the Water Resources Review Committee, staff of the State <br />Engineer met the owners at Red Mesa Ward dam and reservoir to review the physical <br />configuration of the dam and drainage basin. The staff subsequently prepared an alternative <br />determination ofthe IDF and corresponding reservoir and spillway systems capability to <br />safely route the IDF to prevent overtopping of the dam. The results ofthe alternative study <br />were shared with the District's engineers on November 19, 2004. Although the results of the <br />study were preliminary, the study indicated that with some adjustments and refinements to <br />the 30 sq. mile drainage basin runoff parameters, and allowable 10% reduction in the Th\1R <br />PMP, the IDF was reduced 30% and the corresponding spilIway size reduced 50%. The <br />district's engineers are reviewing the alternative study and the staff of the State Engineer is <br />providing assistance as requested. <br /> <br />Long Hollow Reservoir <br /> <br />. <br /> <br />Long Hollow Dam and Reservoir is a project proposed on the Long Hollow drainage, which <br />is tributary to the La Plata River near the Colorado-New Mexico border. The contributing <br />drainage area is 43 sq. miles ranging in elevation from 6,200 ft. MSL to 8,100 ft. MSL. The <br />