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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />combination of headworks location, sediment exclusion. and sediment ejection. Diversion of water <br />from either a natural or man~made channel should - without exception- be on either the outside <br />of a bend or on a straight reach. Sedimem bed material concentration is lowest on the outside of <br />a bend (and highest on the inside); therefore diversion should be made from the pan of the channel <br />wilh the lowest concemration. Exclusion is accomplished by keeping sediment away from <br />headgate opening, usually with a continuously-operating low-level sluiceway. which keeps water <br />with high sedimem concemrations below the headgate sill elevation. Ejection of sediment is <br />accomplished by divening b<mom warer with high sediment concemrations back in to the natural <br />channeL The main Larimer and Weld Canal is welJ-configured for comrol of sedimem in its <br />diversions. <br /> <br />Sedimem diversion can be controlled at farm lUrn-ou(S similarly [0 the headworks control measure. <br />The minimum turn-out elevation should be a least ih foot above lhe supply canal bed elevation. <br />A horizontal lip extending imo !.he canal at the opening inven is also effective in limiting sedimem <br />draw because it precludes an upward flow from the canal bed into lhe gate opening. Where a low <br />gate elevation is necessary for head on the opening, an elevated sill 0 the canal side of the gate can <br />be used. If possible, locating headgates on the insides of bends should be avoided. <br /> <br />Photograph number 3 shows a typical turnout on the inside of a bend and the scour that occurs due <br />to improper placement of the headgate. Any new headgates installed should take into accoum the <br />potential for sedimem rranspon and should be placed as noted above to minimize this. <br /> <br />THE SELECTED PROJECT <br /> <br />The work outlined in the previous seclions was chosen as the best alternatives after reviewing the <br />Company's needs and with the wishes of the Board of Directors in mind. Most StruclUres did not <br />have readily viable altemalives other than a different type of flume, etc. At the beginning of the <br />project, the various water measuring devices were reviewed and the merits of each weighed with <br />regards [0 the conditions encoumered on the ditch. Based on the hydraulic conditions and the type <br />of applications required. we decided to use !.he Repogle Flume for the measuring device on the <br />main ditch, the Cut-Throat Flume on the headgates that supply ditches, and the meter gate for <br />headgates to pump ponds. <br /> <br />These flumes were chosen based on simplicity of construction and use. and due to the hydraulic <br />efficiency of each. The hydraulic efficiency of the measuring devices at the headgates was <br />especially imponam. This is due to the low heads and the minimal grade from the headgates to <br />the fields. <br /> <br />COST ESTD1ATE <br /> <br />The complete breakdown of the COSt of the work proposed is shown in Tables I and .2 with a <br />summary of the costs outlined below. Tables I and 2 shO\\/ the quantity takeoffs and the <br /> <br />Owl Creek Feasibili[)<' <br /> <br />Page 15 <br />