Analysis of Colorado-Big Thompson Project Operation With Respect to East Slope Diversions and Non-Charge Deliveries

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through the current calendar year. For example, water year 1983 began on November 1, 1982 and ended on October 31, 1983. PROJECT BACKGROUND East Slope Facilities Figure 1 is a map showing the C -BT Project facilities on both the east and west slopes. This figure was reproduced from the USBR's 1996 annual operating plan. West slope water is brought into the Big Thompson River drainage through the Alva B. Adams Tunnel and discharged into the East Portal Reservoir on the Wind River, a tributary of the Big Thompson River, at an elevation of approximately 8,260 feet. The capacity of the Adams Tunnel, which was constructed during 1940 -47 and became operational in 1947, is approximately 550 cubic feet per second (cfs). The East Portal Reservoir is simply part of a diversion facility and does not provide reservoir storage capacity for the project. From the East Portal Reservoir, west slope water and some native Wind River water are diverted into the Estes Park Aqueduct and Power System, which consists of the Aspen Creek Siphon, Rams Horn Tunnel, Prospect Mountain Conduit and Tunnel, Marys Lake Powerplant, Marys Lake, and the Estes Powerplant. This aqueduct and power system became fully operational in 1951 and it has a diversion capacity of 550 cfs. Marys Lake provides afterbay and forebay capacity for the two power plants. It has a total capacity of approximately 900 acre -feet, of which 500 acre -feet is active storage. Water from the Estes Powerplant is discharged into Lake Estes, which is formed by Olympus Dam on the Big Thompson River near the City of Estes Park. Lake Estes was constructed during 1947 -49 and placed into service in November 1948. It has a total storage capacity of approximately 3,100 acre -feet at elevation 7,475 feet, of which approximately 2,600 acre -feet is active storage. West slope water and some Big Thompson River water are diverted into the Estes Park - Foothills Power System at Olympus Dam. This power system comprises the Olympus Tunnel, the Pole Hill Tunnel and Canal, the Polehill Powerplant, the Rattlesnake Tunnel, Pinewood Lake, the Bald Mountain Pressure Tunnel, the Flatiron Powerplant, and Flatiron Reservoir and became operational in 1954. The Estes Park - Foothills Power System at Olympus Dam has a capacity of 550 cfs. Flatiron Reservoir regulates water for release to and delivery through the east slope distribution and storage system. Flatiron Reservoir has a total capacity of approximately 760 acre -feet at elevation 5,473 feet, of which approximately 440 acre -feet is active storage. Flatiron Reservoir was constructed during 1950 -53 and placed into service in January 1954. From Flatiron Reservoir, water can be pumped into Carter Lake through a reversible pump /turbine unit or released into the Charles Hansen Feeder Canal. In late 1998 or early 1999, a bypass