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Capacity: <br />At least 2.1 cfs (2.1 cfs was the maximum daily diversion recorded in July 1997) <br />Diversion Measurement Device: <br />East Portal <br />DWR WDID: 3604658 <br />USGS ID: STCTUNCO – Straight Creek Tunnel at East Portal of Eisenhower <br />East Portal Datum: 11,013 feet above sea level NGVD29 <br />West Portal Datum: 11,158 feet above sea level NGVD29 <br />Tunnel Outlet: The 1 foot Parshall Flume is located in a below-ground confined space <br />owned and controlled by CDOT in the Interstate 70 roadway median at the East Portal of <br />Eisenhower Tunnel. Coors coordinates with CDOT for access to the Parshall Flume for <br />readings. Approximately weekly during the run-off period and up to twice a month <br />during other times, except between December a nd February when winter weather makes <br />the Parshall Flume inaccessible, a Coors empl oyee will enter the confined space, clean <br />the flume if necessary, and take a staff ga ge reading. For accounting purposes, readings <br />are carried forward until the ne xt reading is taken. <br />Conveyance Efficiency: <br />The type of construction material used in Straight Creek Tunnel is <br />unknown. Water intercepted in th e Tunnel underdrains is the result of seepage into the <br />Tunnel. <br />HydroBase Data: <br />Continuously monitored streamflow records for Station STCTUNCO are <br />available for daily and monthly divers ions from water year 1995 through 2002. <br />Administrative data for Structure 3604658 are available for daily and monthly diversions <br />from water year 1985 through 2002. Administ rative data for Structure 0704658 are <br />available for daily and monthly diversions from water year 1983 through 2002. Both <br />continuously monitored streamflow records and administrative diversion records are <br />available through Colorado DWR HydroBase. In addition, Coors has maintained daily <br />and monthly accounting records for the St raight Creek Tunnel from 1994 through <br />present. <br />Available diversion data fo r Straight Creek Tunnel was reviewed and compared to <br />identify the best available data source (s hown in Figure 2). M onthly diversions for <br />Straight Creek Tunnel are presented in Table 2. The preferred set of data identified for <br />Straight Creek Tunnel was continuously mon itored data for Station STCTUNCO. When <br />compared to the other available informati on sources, the data for Station STCTUNCO <br />displayed the following characteristics: <br />A long, reliable period of record, <br />Readily available by a vari ety of data users, <br />Corresponding monthly and daily diversi on data available for most of the <br />period of available data, and <br />Continues to be operated as a da ta source through present. <br />StraightCreekTunnel.doc 5 of 9 <br />