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PHYSICAL INFORMATION <br />Roberts Tunnel originates in Water Division 5 Di strict 36 in Summit County and terminates in <br />Water Division 1 District 80 in Park County. <br />In 1942, the first pilot bore for Roberts <br />Tunnel was drilled. Construction of Roberts <br />Tunnel occurred between 1956 and 1962. On <br />July 17, 1964 the first water flowed through <br />the Tunnel. <br />The 10-foot 3-inch diam eter circular tunnel <br />was designed to be operated under pressure. <br />The West Portal of the Tunnel is submerged <br />in Dillon Reservoir, opposite of Dillon Dam. <br />The Tunnel bore is as deep as 4,465 feet <br />below the Continental Divide. The East <br />Portal is one-mile upstream from the town of <br />Grant. The Tunnel was driven from four <br />headings on three courses, with two <br />April 24, 1962-Inspection of entire 23.3-mile long <br />horizontal angles at 5.4 and 8.7 miles from <br />lined tunnel completed. <br />the West Portal, respectively. From the West <br />Portal, Roberts Tunnel extends eastward <br />approximately 8.5 miles to the access shaft loca ted adjacent to the Snake River. The Tunnel <br />turns southeast at the access shaft and continues to the East Portal Outlet Works. The East Portal <br />Outlet Works consist of one 36-inch and two 66-in ch hollow jet valves which discharge into a <br />stilling basin and measuring flume. <br />Length: <br /> 23.3 miles <br />Capacity: <br />1,020 cfs <br />Diversion Measurement Device: <br />East Portal <br />DWR WDID: 3604684 <br />USGS ID: 09050590 - Roberts Tunnel at East Portal near Grant <br />East Portal Datum: 8,667 feet above sea level NGVD29 <br />West Portal Datum: 8,840 feet above sea level NGVD29 <br />Tunnel Outlet: Parshall flume of unknown size equippe d with a Stevens recorder and a <br />satellite linked monitoring system. <br />Conveyance Efficiency: <br />Roberts Tunnel is fully concrete lined. There is a small amount of <br />non-tributary groundwater inflow into the tunne l. The capacity of this inflow is not <br />known. <br />RobertsTunnel.doc 4 of 10 <br />