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of the Denver Water system is included in the documentation for the Upper Colorado River <br />Water Resources Planning Model. <br />PHYSICAL INFORMATION -NORTHERN SYSTEM <br />The Northern system centers on the Moffat Tunnel collection system that conveys transbasin <br />water from the Fraser River and Williams Fork River basins and native water supplies from the <br />South Boulder Creek basin. The Northern system is currently used to supply about 15 to 20 <br />percent of the Denver Water annual demand, which includes a number of treated water service <br />contracts and raw water fixed contract for northern municipalities outside of the City and County <br />of Denver, but within the Denver Water service area. <br />The major structural elements in Denver Water's Northern system are the Moffat Tunnel, Gross <br />Reservoir, South Boulder Diversion Canal, and Ralston Reservoir and the Moffat Water <br />Treatment Plant. The history, operations, and current specifications of these elements of Denver <br />Water's infrastructure are summarized below. Further discussion of the operations of these units <br />with respect to the Denver Water demand is included in the Operational Information section. <br />1) Moffat Tunnel (Structure ID 0604655) <br />The Moffat Tunnel diverts transbasin water from the Fraser River and Williams Fork River <br />basins through the Moffat Tunnel into South Boulder Creek. The tunnel was completed in 1936. <br />The Moffat Tunnel is Denver Water's first transbasin diversion system and is operated in <br />conjunction with Gross Reservoir, the South Boulder Diversion Canal, Ralston Reservoir, and <br />the Moffat Water Treatment Plant. <br />The system currently draws water from the Fraser River and following tributary basins -Jim <br />Creek, Vasquez Creek, Little Vasquez Creek, Ranch Creek, Cabin Creek, Hamilton Creek, Hurd <br />Creek, Trail Creek, Meadow Creek, St. Louis Creek, and Elk Creek. By the end of the 1950s, the <br />Vasquez Tunnel was completed, which brought water from the Williams Fork basin to the <br />Moffat Collection System. Gross Reservoir was completed in 1955 in the upper South Boulder <br />Creek drainage. <br />Specifics regarding the Moffat Tunnel include: <br />• 10' -6" concrete-lined tunnel <br />• Conveyance capacity of 1,360 cubic feet per second (cfs) <br />• Operating capacity is limited by the maximum conveyance capacity in South Boulder Creek <br />below the Tunnel's east portal; therefore, during times of high natural flows in the South <br />Boulder Creek basin, Moffat Tunnel deliveries are limited so that total flows above Gross <br />Reservoir do not exceed about 1,200 cfs <br />• Diversions are measured at the Moffat Water Tunnel at East Portal stream gage (ID <br />09022500) <br />• Pipeline losses are minimal since the tunnel is fully concrete-lined. Measurements at the gage <br />are used to estimate the diversions from the Fraser and Williams Fork River basins. <br />See SPDSS Task S -Key Structure, Moffat Water Tunnel memorandum for further information. <br />Denver Water Board Operating Memorandum 6 of 40 <br />