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I'- .... c.o _. '.'"' SOUTHERN NEVADA WATER AUTHORITY - TREATMENT AND TRANSMISSION FACILITY The River Mountains WTF site proved to be the best choice for the WTF for three reasons: 1. There is no subsurface rock at the site that could require ripping or blasting, which could raise costs, lengthen the schedule, and increase the potential for environmental impacts. Other WTF sites display evidence of subsurface rock; 2. There are fewer site constraints and potential competing uses at River Mountains than at the other two WTF sites; and 3. The River Mountains site is the furthest away from existing residences. These factors overrode the fact that the Foothill site, combined with the Saddle Island intake site, was a slightly less costly alternative. The Railroad Pass site was substantially more expensive due to its greater distance from the best pipeline alignments, Figure 5-1 shows the two transmission routes that connect the Saddle Island intake site to the River Mountains WTF site: 51-1 C and 51-5. Alternative 51-1 C was selected because it is the less expensive of the two. The primary reason it is less expensive is because the existing River Mountains Tunnel can be used; this delays the need to build a new tunnel to reach the WTF site. " '- DESIGNATION OF THE ENVIRONMENTALLY PREFERABLE ALTERNATIVE The Environmentally Preferable Alternative is that alternative which causes the least damage to the environment and best protects natural and cultural resources. The Environmentally Preferable Alternative is not necessarily the Preferred Alternative. For the Proposed Project, they are different. For large construction projects, the Environmentally Preferable Alternative is usually the alternative with the least amount of surface disturbance, especially disturbance in areas where there are potential effects on sensitive plant and animal species. Surface disturbance also generally equates with noise and dust during construction. To determine the Environmentally Preferable Alternative, it is also necessary to consider other human factors such as aesthetics, recreation, and compatibility with existing and planned land uses. Non- environmental factors such as access, engineering, cost, schedule, and contract issues that are important to the selection of the Preferred Alternative are not considered. The approach to the environmental evaluation was to treat each of the five Out-Valley alternatives equally; the In-Valley system for each alternative is identical. Alternative 51-1 C was designated as the Preferred Alternative (the alternative that best meets the stated goals and objectives of the project in an environmentally-sensitive manner). The potentially significant environmental impacts Alternative 51-1 C was selected as the preferred Out-Valley alternative after an independent environmental evaluation of each of the five candidate alternatives. This alternative achieves the objectives and meets the purpose and need of the project in an environmentally- sensitive manner. SUMMARY S-15 --