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Specifics regarding the Roberts Tunnel include: <br />• 23.3 miles of 10'-3" inside-diameter, concrete-lined tunnel that bores 4,465 feet below the <br />continental divide <br />• Estimated operating capacity of 1,020 cfs <br />• Operating capacity is dictated by maximum conveyance capacities in the North Fork South <br />Platte River at Grant and above the confluence with the South Platte River main stem, which <br />are limited to total flows of 680 cfs and 980 cfs, respectively <br />• Diversions are measured at the Roberts Tunnel at East Portal near Grant stream gage (ID <br />09050590) <br />• Pipeline losses are minimal since the tunnel is fully concrete-lined. Measurements at the gage <br />are used to estimate the diversions from Dillon Reservoir and the Blue River basin. <br />See SPDSS Task S -Key Structure, Harold D. Roberts Tunnel memorandum for further <br />information. <br />HydroBase Data <br />Roberts Tunnel diversions are measured at the Roberts Tunnel at East Portal near Grant stream <br />gage (USGS ID 09050590, DWR ID ROBTLTIvTCO). The data available in HydroBase for the <br />1950 to present pertaining to the Roberts Tunnel include the following after it came online in <br />1963: <br />Total River Diversions <br />• Complete record 1963 to present (see Figure 7) <br />• Historical diversions average about 55,000 ac-ft/yr over the 1964 to present period <br />Figure 7 <br />Roberts Tunnel Monthly Diversions <br />28,000 <br />24,000 <br />~ 20,000 <br />d' <br />.. <br />•° 16,000 <br />d <br />A 12,000 <br />0 <br />~ 8,000 <br />4,000 <br />0 - <br />O M ~O O~ N v1 00 ~ h O M ~O O~ N v1 00 ~ <br />v1 v1 v1 v1 ~O ~O ~O h h h 00 00 00 00 O~ O~ O~ O O <br />ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti <br />Denver Water Board Operating Memorandum 13 of 40 <br />