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Vantage to Pomona Heights Chapter 4 230 kV Transmission Line Project FEIS Environmental Consequences PAGE 4-2 The amount of ground that could be disturbed as a result of Project activities was estimated based on the typical design characteristics of this 230 kilovolt (kV) Project (Section 2.2.2). Short-term, long-term, and access road disturbance was estimated and the disturbance model calculations and assumptions are presented in Chapter 2, Section 2.2.3.2. Short-term disturbance included structure work areas for the staging and installation of the tangent H-frame, single pole structures, and angle/dead end structures as well as the conductor pulling and tensioning sites. Long-term disturbance included H-frame, single pole, angle/dead end, and lattice structure base areas as well as work pad areas in slopes over eight percent for equipment stability for structure installation. The amount of ground that could be disturbed as a result of Project activities for the New Northern Route Alternative - Underground Design Option is based on industry standards and methods used on other transmission line projects. The description of the construction components, technologies, methods, and disturbance assumptions are based on other projects implemented by utilities that have installed 230 kV underground facilities elsewhere in the United States and reflect the assumptions detailed in Section 2.2.5. These assumptions include contraction of the continuous concrete duct bank, splice vaults every 1,500 feet, and overhead-to-underground transition stations. Access road construction was assumed to be the same for the Overhead Design Option and the Underground Design Option, with a continuous, permanent 24-foot cleared area and permanent 30-foot ROW. Overhead and Underground Design Option transmission line access for construction would be via a combination of new access roads, overland access, improvement to existing roads and use of existing terrain or roads as is. Where the proposed transmission line would parallel existing transmission lines or other linear utilities, the existing access roads along the existing utilities would be used wherever possible to minimize the amount of new access road construction. In some areas, only temporary roads would be needed. Long-term access roads would be constructed where needed for construction and long-term maintenance. Overland access would occur in areas where no grading would be needed and would be used to the greatest extent possible. Overland travel would consist of “drive and crush” and/or “clear and cut” travel. Drive and crush is vehicular travel to access a site without significantly modifying the landscape (i.e., vegetation is crushed, but not cropped and soil is compacted, but no surface soil is removed). Eight levels of access (Levels 0 through 7) were developed and numerically arranged based on the anticipated ground disturbance expected with Level 0 having the lowest level of ground disturbance and Level 7 having the most disturbance (see Table 2-3). The short-term, long-term, and access road disturbance calculations by route segment and end-to- end Action Alternatives are presented in Section 2.6 and Tables 2-7 through 2-16. 4.1.1.2 Impact Assessment Based on the estimated ground disturbance associated with the Project (Chapter 2) and the resource inventory information reflecting the existing environment, each resource specialist determined the types, level, and amount of impacts that could occur on the resource. Computer-assisted models were developed to support this determination, which allowed the method used for each resource to be tailored to specific requirements and assumptions for analysis of each resource. Qualitative and quantitative variables of resource sensitivity, resource quantity, and estimated ground disturbance were considered in predicting the magnitude of impacts. Four levels were established and defined for each resource: high, moderate, low, and no identifiable impact. A high impact could cause substantial change or stress to an environmental resource or use and would generally be considered a significant impact and could be reduced through mitigation; a moderate impact could potentially cause some change or stress to an environmental resource or use ranging between a significant and insignificant impact and could be reduced through mitigation; a low impact could be a detectable but slight change or stress and would generally be considered an insignificant impact; and a no identifiable impact would be considered where there is no measurable impact to the resource. Mitigation measures applied to the Project may reduce