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<br />f <br /> <br />-~- <br /> <br />. . <br /> <br />Woodward..clyde <br /> <br />Water Supply and Storage Company <br />July 5, 1994- <br />Page 2 <br /> <br />In late spring, following the snow clearing of the Long Draw road by bulldozer, a snow <br />pack in always observed on the face of the dam, usually the full height of the dam <br />(87 feet) and extending out from the top of the dam up to 50 feet during heavy snow <br />fail years. As spring progresses this snow pack compacts due to surface melting and <br />slides down the face of the dam to the toe. As this snow pack slides, materials on the <br />face of the dam become .aturated and small slip-circle slide. have occurred in the past. <br />These slides are normally repaired as they occur on an annual basis. The high winds <br />hlowing through the re,ervoir normally blows the top of the dam free of snow. <br /> <br />During the summer months when the reservoir is full or filling, water is lost to the <br />banks of the reservoir as infiltration, and is stored in the banks until reservoir draw <br />down occurs. <br /> <br />During the winter months the air temperature is usually below freezing most of the <br />time, and temper:l.tures below zero degrees F would not be uncommon. During this <br />time, the reservoir stage gains from approximately two to three feet and I believe that <br />a majority of this water is bank storage outflow from within the reservoir area. Bank <br />water outflow freezes upon reaching the reservoir and' as water flows onto the frozen <br />surface, the ice layer increases in tbick:ne5S and this phenomena is normally referred <br />to as "aufeis". However, some temporary thawing would occur during warm w'".nter <br />days, though in early spring the reservoir surface is normally fraun solid. Aufeis is <br />observed to occur on the downstream side of the dam iu !.he uuLlet plunge puul and La <br />Poudre Pass Creek. <br /> <br />If the outlet gate were to remain open during the winter months, freezing air would be <br />drawn through the outlet conduit causing freezing around the trash rack and within the <br />conduit. There is a high probability that the conduit would eventually be blocked <br />either partially or completely by ice and potentially crack the concrete outlet conduit, <br />jeopardizing the integrity of the conduit and consequently the dam. Ice build up on the <br />downstream side of the outlet gates would probably damage the gate slides and <br />eventually the gates, potentially making them inoperable. I also b<:Iieve that any <br />releases from the dam will add significantly to the ice buildup in the plunge pool and <br />the down stream creek reaches and in further allfeis development within the meadow <br />area downstream of the measuring weir. It is highly improbable that any water <br />released from Long Draw Dam during the deep winter months, would reach Cache La <br /> <br />~llLal 07.0M4(%:14pml/Rl't <br /> <br />-.a-..~4_.dwa"'-cqde CeftlI&.IlIaMa <br />