Laserfiche WebLink
<br />Water Supply and Storage <br />. June 30, 1994 <br /> <br />Page 2 <br /> <br />A fourth concern is that winter releases can also bring about new loading conditions <br />to the rip rap and upstream face in the event water levels lower due to releases. There is an <br />increased potential for unfavorable displacement of riprap, raveling or sliding of material <br />from the face, corresponding safety concerns and mcreased maintenance and repair <br />requirements. <br /> <br />A fIfth concern is that operating the outlet during the winter will cause a temperature <br />gradient between the conduit and the embankment, which can lead to the formation of ice <br />lenses. The ice lenses can fonn in the ~mbankment adjacent to the conduit and result in <br />undesirable voids in the embankment when thawing occurs. The conditions and potential for <br />this problem needs to be considered. <br /> <br />An alternative of pumping water over the dam also raises concern over the safe <br />operation of the dam. Generally, we discourage use of such lines because of the fact that <br />their failure can result in significant erosion problems that could jeopardize the safety of the <br />dam. Our policy in such an instance would require that the pipeline be double encased to <br />reduce the possibility of breaking of the pipeline. Additionally, proper operation of a <br />pumping plant at Long Draw would necessitate daily monitoring of the facility. The <br />remoteness of this dam makes the monitoring program both difficult due to limited access <br />and dangerous to persons conducting such activities. Travel to the dam in the winter would <br />be by snow machine eleven miles one way. During heavy snow or windy conditions the <br />personnel would be at extreme risk. <br /> <br />Also, given the nature of the plunge pool and adjacent nearby flat terrain at the toe of <br />the dam, we expect that water delivered to this area will spread out and freeze. We would <br />therefore expect little water to actually flow past this area immediately below the toe. <br /> <br />In summary, the operation of the reservoir to release 2-1/2 cfs throughout the winter <br />jeopardizes the safety of the dam, places personnel that would be involved in its operation at <br />considerable risk, results in increased costs for repair and maintenance, and is not expected <br />to benefIt flow below the dam. As a result, we recommend against this mode of operation. <br />In addition, any special actions or retrofItting, including associated costs and maintenance, <br />would have to be evaluated extensively prior to installation in order to make the 2-1/2 cfs <br />releases. <br /> <br />Sincerely, . <br /> <br />I{; iJ -.f..,;b- <br />~ D. Sim~on <br />State Engineer <br /> <br />HDS/jhh:lellers:wtrstorg.OO 1 <br />