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<br />0n2100 <br /> <br />S""""""Y <br />watershed and within the CCW-B. The vegetative cover is adequate to facilitate infLltration, and forested areas <br />downslope of roads and ski trails that receive runoff, effectively disperse current levels of runoff and sediments. <br /> <br />When rust-order channels are e1iminated or disrupted through grading the watershed's ability to disperse <br />sediments and runoff is diminished. Prior to the ski area development, runoff from the MCW and CCW was <br />dispersed onto well vegetated slopes and eventually collected by a distinct drainage channel. Ski run construction <br />has disrupted natural flow paths in places where grading has blocked, buried, or rerouted them. Disruption of <br />natural flow paths is especially eviden1 in the MCW. and has led to sediment discharge and reduced water quality <br />in Maroon Creek during the last six years. Runoff and sediments originating from the developed ponion of the <br />CCW are trapped by vegetation and ground litter and do not affect water quality in Castle Creek at present. <br /> <br />According to a recent analysis of water rights in Aspen Highlands. Hines and the Aspen Highland Mountain <br />Umited Uability Company (AHMLLC) jointly own water rights, including I cfs guaranteed supply and 4.5 cfs <br />of interruptible supply, for on-mountain snowmaking and in-house irrigation uses in the Aspen Highlands area. <br />This water is currently being obtained through the City of Aspen's Maroon Creek pipeline and is adequate for <br />existing snowmaking uses and for base area development. The water rights analysis concludes that sufficient <br />protections are provided to prevent out-{)f-priority diversions and injury to the instream flow right by use of water <br />at Aspen Highlands. However, because the interruptible supply from the City of Aspen is not guaranteed, Hines <br />and AHMLLC applied for up to 4.5 cfs of water rights from five alternative take-out points on Maroon Creek <br />as a backup source. These rights were granted under a 1993 decree and Aspen Highlands is curreotly discussing <br />three options with the City of Aspen for delivery of this water. While the water rights analysis concluded that <br />there appears to be sufficient protections to prevent out-of-priority diversions by Aspen Highlands that would <br />violate the 14 cfs minimum instream flow right, the decree granting these rights to alternative sources is currently <br />being appealed by the Aspen Wilderness Workshop. <br /> <br />ENVIRONMENTAL CONSEQUENCES <br />Under the No Action Alternative, impacts would continue for up to 76 acres of snowmaking, located mostly <br />outside the SUP area but totally within the Maroon Creek drainage. The estimated total annual water requirement <br />for tbis amount of snowmaking was 87 acre-feet and the depletion rate would be about 1.08 cfs during the <br />snowmaking periods. It was estimated that, in order not to violate the 14 cfs minimum instream flow right, <br />withdrawals for snowmaking would have to be curtailed during most of December about once every 25 years. <br />However, because dry years would also result in greater reliance by the City of Aspen on maroon Creek for <br />municipal water, it is possible that snowmaking may have to be curtail more frequently or for longer periods. <br />The annual net depletion of all water withdrawals from Maroon Creek under the this alternative would be 2,800 <br />acre-feet. Watashed responses to runoff events would be the same as under existing conditions except for those <br />associated with the Exhibition/Red Onion maintenance road, which is targeted for removal and revegetation. <br />Hillslopes and natural channels in MCW would stay at risk to erosion and potential water yield would not change <br />significantly. Water quality in Maroon Creek would remain susceptible to sedimentation following runoff events <br />without redesigning the current drainage system. <br /> <br />Total annual depletions from Maroon Creek would be 2,943 acre-feet under Alternative B, including 314 acre- <br />feet for additional snowrnaking on a total of 303 acres (227 acres more than under the No Action Alternative). <br />In order to operate the proposed new snowmaking system efficicntly, thc delivery rate of watcr would have to be <br />aboUl4.5 cfs. In order to comply with the 14.5 cfs minimum instream flow requirement, snowrnaking would have <br />to be curtailed between mid-November and throughout the whole of December about one out of every 25 years. <br />which would be a longer period than tmde:r the No Action Alternativc. This period could be increased if the City <br />of Aspen simultaneously places greatcr demand on water from maroon Creek. However, a morc reliablc source <br />of water for snowmaking could bc obtained from scvcral take-out points below the point at which the diversion <br />leading to the hydropowcr plant flows back into Maroon Creek. Spring runoff from snowmaking could result <br />in a 30 acre-feet stream flow accrction in Cas tic Creek. Rclative to the No Action Alternative. these changes <br />would lcad to 65 acre-feet greater depletion from the Roaring Fork basin. Compared to current conditions, <br />Alternative B would result in 8 percent in water yicld in the MCW and a 2 perceot increase in water yield in the <br />Seclion 111 <br />WaleTsMd ResolU'ces 17 <br />