This EIS assesses the environmental effects of constructing 152.1 miles of 230-kV or 230/345-kV transmission line between Thermopolis and Alcova, and between Alcova and Casper. Approximately 136.1 miles of the new 230-kV or 230/345-kV line will either replace two existing but deteriorated 69-kV lines or parallel an existing 115-kV line. The remaining 16.0 miles of line will be constructed on a new corridor. In addition, approximately 50.0 miles of 69-kV line will be reconstructed at 69/115-kV between Arminto and Casper. Other minor elements of the project include construction of short 34.5-kV and 69/115-kV connecting lines, and a new substation near Alcova. The purpose of the project is to bring the regional transmission system into compliance with National Electric Reliability Council criteria and to reduce energy losses associated with overloading of the existing system. Alternatives assessed include no action, delay, reduction in the quality of electrical service, alternative transmission technologies, alternative design, and alternative routes. Significant impacts include soil disturbance and increased erosion, potential disturbance of sensitive habitats for sage grouse, bald eagles and raptors, and increased visual impacts created by the replacement of small, wood structures with larger transmission structures.