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SPDSS Task 4 Memorandum <br />November 23, 2004 <br />Roberts Tunnel <br />Roberts Tunnel began diverting water to the South Platte basin in 1964. <br />• Administrative data for Structure 3604684 are available sporadically from 1971 <br />through 2002. Continuously monitored streamflow data and administrative data <br />are the same for most years for which both sets of data are available, with the <br />exception of 1989, 1990, and 1991. The reason for these discrepancies is not <br />clear. <br />Comparison of the continuously monitored streamflow data for Station 09050590 <br />and Denver Water data indicated differences between the two sources of data. <br />These differences may be the result of the point at which diversions are measured. <br />It is understood that Station 09050590 measures diversions at the East Portal of <br />Roberts Tunnel, while Denver Water measures diversions at the West Portal of <br />the Tunnel. <br />Continuously monitored Station 09050590 represents a complete set of diversion <br />data for the SPDSS study period and is the preferred source for historical and <br />future diversion data for Roberts Tunnel. <br />Straight Creek Tunnel <br />Straight Creek Tunnel began diverting water in 1973. Water carried in Straight Creek <br />Tunnel comes from two sources; a transmountain diversion that is piped under the <br />Continental Divide for industrial use at the tunnel, and tunnel seepage. Water from both <br />sources is discharged into Clear Creek. <br />The Straight Creek Tunnel recording device is located in a confined space with limited <br />access. The recording device is accessed by Coors Brewing Company personnel weekly <br />during the run-off period and up to twice a month during other times, except between <br />December and February when winter weather makes the recording device inaccessible. <br />When accessed, the flume is cleaned if necessary and a staff gage reading is taken. The <br />diversion data recorded at the diversion recording device is provided by Coors to the <br />State hydrographer who uses the data to develop the continuously monitored station data <br />for Station STCTLTNCO. The State hydrographer in turn provides the diversion data to <br />the Water Commissioners in Districts 36 and 7. The Water Commissioner for Division 5, <br />District 36 develops the administrative records for Structure 3604658 and the Water <br />Commissioner for Division 1, District 7 develops the administrative records for Structure <br />0704682. These four data sources were reviewed and compared to identify the best <br />available data source. <br />• Continuously monitored streamflow data for Station STCTLTNCO are available <br />for daily and monthly diversions from 1995 through 2002. <br />• Administrative data for Structure 3604658 are available for daily and monthly <br />diversions from 1984 through 2002. <br />• Administrative data for Structure 0704658 are available for daily and monthly <br />diversions from 1982 through 2002. <br />• Coors has maintained daily and monthly diversion records through Straight Creek <br />Tunnel from 1995 through present. <br />Page 12 of 19 <br />