Orono Substation Expansion - Enviromental Assessment (1)

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Table 1: Percent and Type of Right-of-Way Followed I Existing Right-of-Way Type and Miles Followed Route BNSF RR U.S. New/Cross Country Total Length Highway 12 Proposed 0.34 miles, N/A 0.25 miles (0.16 miles, 866 feet 0.59 miles Route 57 percent on Xcel Energy Property) Baker Park N/A 0.25 miles 0.16 miles (all on Xcel Property) 0.41 miles Reserve Alternative 3.7 Conductors High-voltage transmission line circuits generally consist of three phases,each at the end of a separate insulator,and physically supported by structures or poles. A phase consists of one or more conductors (single,double,or bundled). A typical conductor is a cable consisting of aluminum wires stranded around a core of steel wires. Shield wires are strung above the phases to prevent damage from potential lightning strikes. The shield wire may also include a fiber optic cable that allows for substation protection equipment to communicate with other substation terminals on the line. The phases for this project would be constructed with three single steel supported aluminum conductors (ACSS) which each consist of a single conductor comprised of seven steel core strands surrounded by 26 outer aluminum strands. The separate conductors are 795,000 circular mils or approximately 1.092 to 1.139 inches in diameter. The ground to conductor height depends on overall topography and man-made obstacles and will meet or exceed the minimum clearance requirements of the National Electric Safety Code (NESC). Two 3/8th inch diameter extra high strength steel,seven strand shield wires will be installed to protect from lightning strike. Ultimately, the transmission line would be three-phase,60 hertz (Hz),alternating current line. 3.8 Structures Xcel Energy proposes to use a combination of three different structure types (Table 2). All of the proposed structures would be single pole structures constructed of galvanized or weathering steel with heights of between 70 and 115 feet,depending upon the structure type and location (Xcel Energy,June 7,2011,and Xcel Energy,personal communication,October 13,2011). All structures are anticipated to be self-supporting;Xcel Energy does not anticipate use of structures requiring guy wires (Xcel Energy,personal communication,November 4,2011). Examples of the structure proposed structure types are shown in Figure 2. i 1 Environmental Assessment PUC Docket E002/TL-11-223 Page 10