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Vantage to Pomona Heights Chapter 4 230 kV Transmission Line Project FEIS Environmental Consequences PAGE 4-6 (WNHP) and/or BLM. The WNHP GIS occurrence polygons include large buffers; therefore, it is uncertain if the occurrences actually intersect with areas of impact from the proposed Project. For the purposes of this analysis, the assumption is made that the entire mapped area is occupied by the species. The WNHP does not disclose special status plant occurrence information for private lands due to privacy laws. Therefore, without surveys on private lands, there is no way to disclose what effects the proposed Project may have on special status plants on private land. For the New Northern Route (NNR) Alternative - Underground Design Option, the analysis assumed that open cut trenching would be used for the entire length of the underground section/route segment. Open cut trenching is the most common method of construction for underground transmission line installation. Also for the NNR Alternative - Underground Design Option, it was assumed that underground splice vaults would not be placed in or near stream and drainage course crossings. Refer to Section 4.14 for more information on impacts to water resources. 4.2.1.2 Impact Criteria Sensitivity classifications were assigned to vegetation resources that occur within the Project study area. These sensitivity classifications served as the basis for the assigning of impact levels. Criteria used to assign resource sensitivity included species’ legal status (federally listed and Candidate species; BLM and state sensitive species) and biologically important plant communities (wetlands, riparian areas, aspen, and sagebrush). Table 4.2-1 summarizes the resource sensitivity classification for vegetation resources that occur in the Project area. Table 4.2-1 Vegetation Resource Sensitivity Classifications VEGETATION RESOURCE SENSITIVITY POTENTIAL IMPACT FROM THE PROPOSED PROJECT Riparian, Perennial Streams/Wetland High Reduction in a fragile sensitive habitat. Sagebrush/Perennial Grassland, Bitterbrush/Perennial Grassland High Reduction in quality habitat that supports sensitive obligate species and is slow to recover from disturbance. Special Status Plant Species Occurrences1 High Disturb fragile populations of species and reduction in special status species habitat. Trees High Reduction in quality habitat that supports sensitive obligate species and is slow to recover from disturbance. Rock/Basalt Cliffs Moderate Reduction in quality habitat that supports sensitive obligate species and is limited in distribution. Intermittent Stream or Dry Gully Moderate Reduction in habitat (abundance and quality) that is slow to recover to pre-disturbance state. Sagebrush/Annual Grassland and Rabbitbrush/Annual Grassland Moderate Reduction in habitat (abundance and quality) that is slow to recover to pre-disturbance state or is at-risk of further degradation. Annual Grassland, Perennial Grassland Low Reduction in habitat (abundance and quality). 1Based on 2011 and 2013 survey data (Appendix B-3) and WNHP buffered occurrence data (WNHP 2015a). 4.2.1.3 Impact Types Impacts to vegetation resources were measured on multiple scales. Impacts can vary in intensity from no change or only slightly discernible change to a full modification of the environment. In addition to the intensity of impacts, duration of impacts was considered. Duration was evaluated in terms of short-term and long-term impacts. The general types of impacts caused by the construction, operation, and maintenance of the proposed Project are presented in Table 4.2-2.