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EXECUTIVE SUMMARY <br />WINDY GAP FIRMING PROJECT DRAFT ENVIRONMENTAL IMPACT STATEMENT <br />Alternative 5 <br />Alternative 5 is a combination of a 60,000 AF Dry Creek Reservoir on the East Slope and a 30,000 AF <br />Rockwell Reservoir on the West Slope (Figure ES -4). Water deliveries to and from Rockwell Reservoir <br />would require a new pipeline and connection to the existing Windy Gap pump station. A new 3.4- mile -long <br />pipeline connection to C -BT facilities would convey Windy Gap water to Dry Creek Reservoir. A new 2.1- <br />mile -long pipeline also would be needed to deliver water from Dry Creek Reservoir to Carter Lake. As with <br />Alternatives 3 and 4, the availability of a new West Slope reservoir would allow water diversions from the <br />existing Windy Gap Reservoir to be delivered to either Rockwell Reservoir or Granby Reservoir. When <br />Granby Reservoir is full or the Adams Tunnel is at capacity, Windy Gap water would be diverted and stored <br />in Rockwell Reservoir until there is sufficient capacity to transfer water to Chimney Hollow Reservoir. <br />ENVIRONMENTAL EFFECTS <br />The WGFP would result in environmental effects to a number of resources. The effects of all of the action <br />alternatives related to increased water diversions would be similar because similar amounts of water would be <br />diverted from the Colorado River. The No Action alternative would result in similar, but smaller, effects <br />because Windy Gap diversions would increase in the future with a higher water demand even though the <br />enlargement of Ralph Price Reservoir would only increase storage for Windy Gap water by 13,000 AF. This <br />summary focuses on those resources with the greatest potential impacts. Effects on ground water, geology, <br />soils, air quality, noise, cultural resources, and visual quality are expected to be minimal and are not discussed <br />in this summary. Impacts to these resources are discussed in detail in the DEIS. The following sections <br />summarize the effects to other resources. Proposed mitigation is discussed at the end of this summary. <br />Surface Water Hydrology <br />The WGFP would result in increased diversions and reduced flows in the Colorado River below Windy Gap <br />Reservoir. In many years, the flows would be unchanged, but in wetter years, diversions would increase, with <br />a corresponding decrease in Colorado River flows. Estimated average annual flow changes from hydrologic <br />modeling are described below. <br />• Windy Gap diversions would increase about 7,000 AF per year on average from existing conditions <br />under the No Action alternative compared to an increase of about 9,500 AF for the Proposed Action, <br />and an increase of 12,000 AF for the other alternatives (Table ES -2). <br />• Colorado River average annual flow below Granby Reservoir would decrease about 7 percent (4,000 <br />AF) under the No Action alternative, 15 percent (9,000 AF) under the Proposed Action, and 12 to 13 <br />percent for the other alternatives as a result of the availability of additional Windy Gap storage and <br />fewer reservoir spills (Table ES -2). <br />• Colorado River average annual flow below the Windy Gap diversion would decrease by 8 percent <br />(12,000 AF) under the No Action alternative compared to a 14 percent (21,000 AF) decrease for the <br />action alternatives (Table ES -2). The majority of the reductions in flow would occur between May <br />and August (Figure ES -5) with average monthly flow reductions up to 20 percent for the No Action <br />alternative, 23 percent for the Proposed Action, and 28 percent for Alternatives 3 to 5. The average <br />monthly percent flow reduction would be greater in wet years. In dry years, there would be no <br />change in flow from existing conditions. <br />ES -8 <br />