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Vantage to Pomona Heights Chapter 4 230 kV Transmission Line Project FEIS Environmental Consequences PAGE 4-66 supply. Because existing transmission lines near the southern part of the Project study area are located outside of JBLM YTC, raven nest data are not available in these areas. Because raptor and corvid populations are not likely to be limited by availability of nesting and perching substrates in areas where those resources currently exist, it is reasonable to expect the effect of new transmission structures to be greatest where other tall structures, including transmission lines, do not currently exist. All Action Alternatives parallel existing transmission lines for at least part of their length. As part of the proposed Project design, whenever feasible, new transmission line structures will be placed in sync with existing nearby transmission line structures. Given the territorial nature of raptor and corvid species and density limitations imposed by food availability, it seems unlikely that adding a new transmission line structure within 0.25 mile of a similar existing structure would have much, if any, effect on the nesting density of corvids or raptors. That said, the new perches could increase the amount of landscape that is within view of a perch and slightly widen the corridor of increased predation risk. To assess impacts to wildlife species from the presence of additional perching sites, the total number of structures per route segment was estimated. In general, the number of perching opportunities for a given route segment is directly related to its length. Table 4.3-5 presents the number of transmission line structures for the proposed Project by route segment as well as the number of structures that will be located greater than 0.25 mile from an existing transmission line structure. As discussed in the previous paragraph, new structures in new areas are likely to have a higher impact than new structures in close proximity (less than 0.25 mile) to existing structures because they may encourage predators to occupy previously unoccupied areas. The proposed Project would not result in any new structures farther than 0.25 mile from existing structures for Route Segments 3a, NNR-4, NNR-6, NNR-7, or NNR-8. Other route segments, for which fewer than half of the transmission line structures would be farther than 0.25 mile from existing structures, include Route Segments 1a/NNR-1, 2c, NNR-2, and NNR-3. Table 4.3-5 Summary of New Transmission Structures that would be Installed by Route Segment ROUTE SEGMENT LENGTH OF ROUTE SEGMENT (MILES) LENGTH (MILES) AND PERCENT OF ROUTE SEGMENT LOCATED >0.25 MILE FROM AN EXISTING TRANSMISSION LINE TOTAL ESTIMATED NUMBER OF NEW STRUCTURES TOTAL ESTIMATED NUMBER OF NEW STRUCTURES LOCATED >0.25 MILE FROM AN EXISTING TRANSMISSION LINE 1a/NNR-1 2.4 1.1 (44%) 31 14 1b 12.5 12.0 (96%) 89 85 1c 12.9 12.3 (95%) 92 88 2a 1.0 1.0 (100%) 7 7 2b 16.3 16.3 (100%) 116 116 2c 18.1 8.8 (48%) 124 60 2d 7.0 7.0 (100%) 50 50 3a 0.1 0.0% 3 0 3b 21.7 19.2 (88%) 181 160 3c 25.2 16.1 (64%) 186 119 NNR-2 5.1 2.0 (40%) 48 21 NNR-3 9.3 0.6 (7%) 69 5 NNR-4o* 4.5 0.0% 35 0 NNR-4u* 4.5 0.0% 4 0 NNR-5 1.8 1.2 (67%) 16 10