Vantage to Pomona FEIS Index 34 - Laserfiche WebLink

Home Browse Search

Vantage to Pomona Heights Chapter 3 230 kV Transmission Line Project FEIS Affected Environment PAGE 3-61 approximately five miles, though movements of up to 20 miles have been recorded for adult females in Washington. Sage-Grouse in the YTC population are non-migratory with only localized movements between seasonal use areas, whereas some birds in the Mansfield Plateau/Moses Coulee population exhibit migratory patterns (Robb and Schroeder 2012). The WHCWG completed a statewide connectivity analysis (WHCWG 2010) and a Columbia Plateau connectivity analysis (WHCWG 2012), including a species-specific connectivity analysis for Sage- Grouse (Robb and Schroeder 2012). Sage-Grouse-specific WHCWG analyses identified four Habitat Concentration Areas (HCA) within Washington. These include the YTC and Mansfield Plateau/Moses Coulee populations already mentioned and two reintroduced populations, one in the northern Crab Creek drainage in Lincoln County and one on the Yakama Indian Reservation in Yakima County. Sage-Grouse were translocated to the Yakama Indian Reservation in 2006, but, as of 2012, there were no confirmed observations of breeding activity (Robb and Schroeder 2012). The WHCWG analyzed connectivity among the four HCAs by assigning resistance values to various land covers and anthropogenic features along potential routes that Sage-Grouse may take if they attempted to travel from one HCA to another. The resistance values relied upon published literature and the professional judgment of biologists and expert reviewers. Resistance values for anthropogenic features ranged from 0 (e.g., 1,640 to 3,280-foot buffer of 230 kV transmission line) to 99 (housing with less than 10 acres/dwelling unit). Transmission lines were given a resistance value of 7 for single 230 kV line and 3 for 1,640-foot buffer. For two adjacent 230 kV lines the resistance values were not doubled, but increased by approximately 25 percent (9 for double line; 4 for 1,640-foot buffer; 1 for 0.6-mile buffer; Robb and Schroeder 2012). The WHCWG analysis identified the linkage between the YTC HCA and the Mansfield Plateau/Moses Coulee HCA as “fairly good” (see Figure 3.3-3). Much of the habitat along this corridor is shrub-steppe that is protected within state-owned wildlife areas. Impediments to this linkage include the relative steepness of the terrain, disturbance associated with I-90, several existing transmission lines, and two wind energy developments. Conditions for movement are best in the central portion of the linkage, but there are areas of concern at both ends. Near its northern end, the modeled corridor is constricted as it crosses the Columbia River near Rock Island Dam. Near the southern end, north of I-90 and the proposed Project, the linkage is constricted by two wind energy developments (Robb and Schroeder 2012). Sage-Grouse Population Range Estimates Based on location data provided by JBLM YTC, including telemetry data and incidental observations, it is apparent that within the JBLM YTC, some areas are more heavily used by Sage-Grouse than others (Figure 3.3-2). To generate a clearer picture of relative density of use by the YTC Sage-Grouse population, a fixed kernel density analysis was conducted using telemetry data. The methodology is explained in detail in Appendix B-5 Sage-Grouse Technical Report. The kernel density method is commonly used to compute probabilistic estimates of utilization distribution within individual animal home ranges, using random location data consisting of discrete points (Fuller et al. 2005). While most often used to estimate distribution of use for individuals, the method has also been used to estimate utilization distribution for populations (Coates et al. 2013). To yield easily interpretable metrics, 95 percent and 80 percent isopleths were generated in our analysis. Areas within the isopleths represent probabilities of utilization. The 95 percent isopleth encompasses 95 percent of the predicted distribution of all grouse habitat use for the YTC population; for the lay reader, this concept can be roughly understood in the following way: on an “average” day, 95 percent of the grouse would be expected to occur within the 95 percent isopleth, or alternatively the “average” grouse spends 95 percent