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for the SPDSS planning effort, which will require identification of the amount of irrigated <br />acreage within municipalities. We recommend using the results of Cottonwood Curve method <br />analyses conducted by Westminster and Brighton as a default in the SPDSS model: <br />• CU rate of 83 percent and associated LIRF rate of 17 percent <br />• LIRF rate includes 2 percent immediate surface water returns (part of miscellaneous <br />outside uses discussed above) and 15 percent lagged ground water returns <br />This approach will tend to calculate a conservative CU rate associated with municipal water <br />users' outside demands. <br />LIRF analyses typically account for the location(s) of return flows above major downstream <br />ditch headgate(s) in relation to the location of the municipal service area. Accounting for the <br />timing of LIRFs is sometimes simplified with 12 factors (e.g., Sterling) or lagged monthly via <br />the Glover method or using results from a MODFLOW model (e.g., Aurora, Brighton, Denver, <br />SACWSD, Thornton, and Westminster). The LIRF analyses either reviewed or discussed with <br />municipal personnel indicate a wide range of timing for LIRFs. We recommend using LIRF <br />return flow timing and location data obtained from users, or using lagging patterns and locations <br />based on Glover analyses or the future SPDSS alluvial ground water model. <br />Self-Supplied Industrial Water users Consumptive Ilse <br />The CU rates for self-supplied industrial users were estimated based on user information or <br />similar industries' CU rates when user-supplied information was not available. The CU rates for <br />these uses are summarized in Table 6. The power plants consume between 47 percent and 100 <br />percent of their respective water demands, depending upon the type of facility (i.e., natural gas <br />versus coal-fired). The CU rate estimated by the Coors brewery is currently 10 percent of the <br />demand and has historically been at a similar rate, which is due to a large amount of its water <br />supply used for cooling purposes. The CU rates for snowmaking at the two ski resorts was <br />estimated at 30 percent based on the Loveland Ski Area decreed value (Case No. 88CW246). <br />Snowmaking returns are generally accounted for during the spring runoff (e.g., May and June) <br />measured in nearby stream gages. <br />Table 6 <br />Self-Supplied Industrial User <br />Consumptive Use Rates <br />Facility CU Rate <br />Cherokee Power Plant 75% <br />Valmont Power Plant 53% <br />Eldora Ski Area 30% <br />Loveland Ski Area 30% <br />Arapahoe Power Plant 90% <br />Coors Brewery 10% <br />Rawhide Power Plant 100% <br />Pawnee Power Plant 100% <br />Fort St. Vrain Power Plant 47% <br />Task 66.2 Memorandum.doc Page 15 of 26 <br />