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The Operations Plan is for two types of operations of the reservoir descxibed: Normal Operations and Ernergency Operations. Normal Operations are the typical operations of the reservoir. The reservoir is filled duYing spring runoff while maintaining a base flow of 0.5 cfs downstream of the diveYSion. The Yeservoir fills by eaYly June mostyear.r, and then diversions teYminate as the opportunity to use the pxoponents' water Yights would be exhausted. This scenario of use, was developed by the proponents' water engineer to utilize available flows, divexsions, and storage space to serve proponent demands, and then modeled by Resource Engineering, Inc to disclose potential impacts. In the myriad of scenarios possible under diffexent watex yeaYS and the vaYious opexations of the othex wateY supply facilities in the Upper Colorado Rivex Basin, the full use of available water rights may not be achieved in early June and divexsions to refill Yeservoix capacity may continue lateY into the year. In all years, minoY diversions will continue thYOUgh the summer to maintain the created wetlands (0.25 to 0.33 cfs). Stoxed water is used by xeleasing water fxom ODR to Dillon Reservoit or Salt Lick Gulch, foY Sununit County, Town of Dillon, and the Town of Silverthoxne. The operations may divert moxe water, up to 450.12 acre-feet annually, than the 286 acre-feet of physical capacity of the enlarged reservoit, because water is released from storage during the reservoir fill pexiod and watex may be exchanged through the reservoix. Divexsions from Salt Lick Gulch are not planned during the winter under Normal Operations. Emergency Operations would occuY only when the Town of Dillon's domestic water supply, Straight Creek, is not available foY divexsion to the town's water treatment plant due to quality ox quantity deficiencies. Straight Cxeek parallels I-70 and the watershed has expexienced moYtality in the Lodgepole Pine foxest due to the pine beetle epidemic. Straight Creek could be contaminated by a hazaxdous waste spill from an accident on I-70, ox a catastrophic wildfixe in the watershed could cYeate such a high sediment load that the town's water treatment plant would not be able to treat the incoming water. Emergency Operations will go into effect when a water quality sample for turbidity at the Town's diversion indicates the treatment facilities threshold has been exceeded, when a chemical contamination occurs, or if the flow in Straight CYeek is too low due to drought conditions to meet Dillon's e~sting demand. The Town's wateY treatment plant is capable of tteating raw water up to 60 nephelometric turbidity units (NTUs). 2.4 Project Descxiption-Analysis of Altexnatives and Selected Alternatives 2.4.1 Analysis of A1teYnatives The "Preliinulary Scoping Document Old Dillon Reservoir Expansion" 1995 (.ree Preliminary Scoping Document, Exhibit I) looked at multiple A1teYnatives: Altexnarive 1: No Acrion Alternative 2: No Expansion- Change OpeYating PYOCeduYes Alternative 2A: Use by the Town of Dillon Alternative 2B: Modify Facilities to Improve Mixing Alternative 3: Small Expansion AlteYnative 4: Ma~mum Expansion 10