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Lake McIntosh Reservoir Company Agenda Item 18b <br /> January 25-26, 2016 Board Meeting(Updated January 27, 2016) <br /> Page 3 of 5 <br /> Oligarchy Ditch is entitled to is instead diverted into the Highland Ditch. Concurrently, the same <br /> amount of water is released from the Reservoir to the Oligarchy Ditch in exchange. On average, the <br /> Company delivers 1,533 AF per year to its shareholders. <br /> Project Description <br /> The goal of this Project is to restore the Reservoir's functionality by repairing its damaged outlet <br /> works. In discussions with the State Engineer's Office Dam Safety Branch (SEO), it was found that the <br /> Reservoir did not meet current outlet works drawdown requirements. For new reservoirs, the SEO <br /> requires the outlet works system be able to release the top five feet of the reservoir in five days. The <br /> existing outlet works was capable of drawing down the top five feet of the Reservoir in thirteen days. <br /> The SEO's position is that any repairs to existing outlet works systems cannot decrease the current <br /> drawdown time, while increasing the release capacity towards the five day new reservoir standard is <br /> preferred. The following alternatives were considered: <br /> Alternative 1 - Do Nothing: This alternative was considered unacceptable. Without a gravity outlet <br /> works, shareholders would have to rely on a temporary pumping system to operate the water <br /> exchange. Additionally, the Reservoir would not be able to release stored water during an emergency <br /> situation which would violate the SEO's requirements, leading to a storage restriction. <br /> Alternative 2 - Replace 24" VCP, CIPP Liner: This alternative would seek to repair the damaged VCP <br /> pipes with a cured in-place pipe (CIPP) procedure. A hydraulic analysis showed this alternative would <br /> reduce the pipe's inside diameter from 24-inches to 23-inches; decreasing the outlet works release <br /> capacity. This would violate the SEO's requirements and thus is considered not feasible. <br /> Alternative 3 - Replace 24" VCP, Pipe Splitting: This alternative would involve splitting one of the <br /> existing 24" VCP pipes and installing a larger diameter HDPE pipe to replace the two VCP pipes. To <br /> maintain minimum release capacities a 34-inch HDPE pipe would be needed. The engineer raised <br /> constructability concerns in maintaining the precise grade needed and limited room for staging the <br /> HDPE pipe. This alternative was considered to be neither economical nor feasible. <br /> Alternative 4 -Abandon Outlet Works, Install Permanent Pump Station: Due to the grade of the <br /> Oligarchy Ditch and the Reservoir's outlet, the outlet pipe runs 3,300 feet before it catches grade and <br /> can discharge into the Oligarchy Ditch by gravity. This alternative would abandon the entire outlet pipe <br /> and instead pump up to the ditch by installing a permanent pump station. The construction cost is <br /> estimated to be $4 million dollars without consideration of annual operation and maintenance cost <br /> because of the size of pump required to meet the SEO drawdown requirements. This alternative was <br /> not selected as it is not economical. <br /> Alternative 5- Repair Outlet to Irrigation Capacity, New Emergency Outlet: This alternative looked <br /> at the feasibility of repairing the existing outlet with a smaller pipe to maintain irrigation release <br /> capacities, and constructing a new outlet that can provide the SEO required emergency release <br /> capacity at a new location. This presented multiple challenges and potentially high costs due to the <br /> easements and land acquisitions that would be necessary and the multiple entities that would have to <br /> be involved (City of Longmont, Ditch Companies, Parks Department, Homeowners). With uncertain site <br /> conditions, cost associated with a new structure, and the required repairs to the existing outlet to <br /> maintain releases to Oligarchy Ditch, this alternative was not considered further. <br /> Selected Alternative 6- Replace 24" VCP, RCP Pipe: This alternative involves replacing the two <br /> 24-inch VCP pipe section, with one 48-inch reinforced concrete pipe (RCP). This pipe type would match <br /> the downstream pipe section and be capable of drawing down the Reservoir's top five feet in seven <br /> days (88 cfs). This meets the SEO's drawdown requirement as it's the maximum rate that can be <br />