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Vantage to Pomona Heights Chapter 4 230 kV Transmission Line Project FEIS Environmental Consequences PAGE 4-74 Because the proposed NNR Alternative closely parallels an existing Pacific Power 230 kV transmission line as it crosses the identified linkage area, the magnitude of its effect on Sage-Grouse movement will depend on a number of unknown variables, including the perception of the vertical structures by Sage- Grouse, and the potential for the structures to attract avian predators. The proposed NNR Alternative would impede Sage-Grouse movement, but only to the extent that Sage-Grouse avoid the transmission line (refer to the Behavioral Avoidance of Infrastructure discussion above). There is no research indicating how the width of a disturbance corridor (such as a transmission line ROW) influences Sage- Grouse movement. The resistance values assigned by WHCWG indicate that they predict that adding a second transmission line to an existing ROW corridor will increase the existing impediment by roughly 25 percent. The NNR Alternative - Underground Design Option could alleviate Sage-Grouse avoidance of the NNR Alternative; however, two existing 500 kV and two existing 230 kV transmission lines, I-90, and the two existing wind developments would still be present on the landscape. Based on information provided by the kernel density analysis, it appears that Sage-Grouse use of the area north of the proposed NNR Alternative has been limited, even two decades ago when the YTC population was higher (over 400 birds). The impact of the proposed NNR Alternative also depends on the behavior of Sage-Grouse relative to other landscape features located between the two populations. If no movement occurs between the two populations currently, then adding an impediment would not result in a change. Genetic evidence suggests that currently there may be little movement between the two populations. Nevertheless, the effort by WHCWG to evaluate the linkages indicates motivation to restore and enhance connectivity and it is possible that impedance to movement by other existing landscape features in the linkage zone could be ameliorated in the future. To minimize the potential for predation and behavioral avoidance and, thus, the impedance to movement and connectivity, the following RDFs would be implemented: the NNR Alternative would closely parallel the existing Pacific Power 230 kV transmission line, with transmission centerline separation typically staying within 200 to 300 feet; whenever possible, locations of the new structures will match the spans of adjacent transmission lines; and perch deterrents will be installed on transmission line structures within four miles of active leks. Given the current location of active leks, perch deterrents will be installed on transmission line structures within a four mile stretch of Route Segment NNR-6 that is within the most likely zone for movement between populations to occur. The RDFs would likely minimize the benefits to avian predators (discussed in Section 4.3.3.2), which would reduce Sage-Grouse avoidance due to predators. These RDFs may also minimize the visual impact of the transmission line structures on Sage-Grouse which would reduce an avoidance effect of the structures. Potential mitigation actions to compensate for residual connectivity impacts are described in Appendix B-6 - Framework for Development of a Sage-Grouse Compensatory Mitigation Plan. 4.3.3.5 State Listed and Other Special Status Species Special status species or other species of particular concern will be considered in accordance with management policies set forth by appropriate land management agencies (e.g., BLM, JBLM YTC, Washington State Department of Natural Resources, and the U.S. Bureau of Reclamation). In cases where such species are identified, appropriate action will be taken to avoid adverse impacts on the species and their habitats. Fish, Amphibians, and Invertebrates Several special status aquatic species have the potential to occur within the Project study area, especially along the Columbia River and Yakima River, as described in Section 3.3.2.3. Coho salmon (Oncorhynchus kisutch), leopard dace (Rhinichthys falcatus), and mountain sucker (Catostomus