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3. Construction Alternative 2 - Relocate the Control Gate <br />This alternative considers abandoning the existing gate building and the use of the vertical shaft to <br />house the control gate and operator. The gate will be relocated to the downstream end of the <br />outlet tunnel and a new pipe will be installed from the existing gate to the downstream end of the <br />existing outlet pipe. A general summary of the work proposed follows and preliminary details <br />considered are shown on Figure 6. <br />To relocate the control gate from the current location in the outlet shaft to the he downstream end <br />of the outlet tunnel will not require the removal of the existing wooden landings and the body of <br />the existing gate can remain in place as long as the gate disc is fully opened or removed from the <br />gate valve housing. Access to the gate valve can be obtained, if needed, by removing the rocks <br />currently piled on the downstream end of the outlet tunnel and saw cutting a hole through concrete <br />wall separating the shaft from the tunnel. <br />To repair the hole in the pipe and to relocate the gate valve location a 24 -inch pipe will need to be <br />grouted into the existing 30 -inch pipe and a pipeline will need to extend from the shaft to the new <br />gate location at the downstream end of the outlet tunnel. The new 24 -inch pipe will be gasketed <br />PVC pipe, the gasketed pipe has room to allow for expansion and contraction due to fluctuations in <br />temperature. <br />At the new gate location a new enclosure will need to be constructed to protect the gate valve from <br />falling rocks and from the freezing temperatures that occur at the 11,000 foot elevation. The <br />enclosure will also be installed to allow for access to the outlet tunnel and to protect against <br />freezing temperatures around the new outlet pipeline. The 40 feet of 30 -inch pipe that exists <br />downstream of the outlet tunnel and the new enclosure will be lined with PVC pipe to protect the <br />outfall from the reservoir from being cut off due to falling rock. <br />The existing shaft will be sealed off to protect the public from harm and the existing building will <br />be demolished to protect the public. <br />The complete breakdown of the work proposed and the cost of the work proposed for Alternative 2 <br />for Lake Isabelle is shown in Table 6. Due to the unique nature of this project Left Hand <br />Excavating helped in the determination of the costs for the Lake Isabelle Rehabilitation <br />Alternative 2. <br />Allen Lake and Lake Isabelle - 12.012 <br />Left Hand Ditch Company Page 17 <br />