Where the I-5 Corridor Reinforcement Project
Could be Located
Map and description of the I-5 Corridor Reinforcement Project Environmental Impact Statement project area.
The I-5 Corridor Reinforcement Project EIS will cover the area in southwestern Washington and northwestern Oregon as shown on the project maps (overview map and interactive map). The project includes crossing the Columbia River.
How Routes are Developed
Engineers consider many factors as they begin the process of developing potential routes for a transmission line. First, transmission system planners determine the beginning and ending points for the proposed transmission line (for this project a new line would connect to existing 500-kilovolt lines at a new substation in the Castle Rock, Wash. area and an existing substation at Troutdale, Ore.).
Then the engineers consider the type of towers required and amount of right-of-way needed for safety clearances. The proposed I-5 transmission line would require a 150-foot wide right-of-way, which is typical for lines of this voltage. Tower sites also must be accessible for construction and for maintenance, so road access must be possible.
With the technical requirements outlined, routing engineers then consider how a new line could impact people, plants and animals, farms, timber production, businesses and important local and regional features. They look for ways to site a line to avoid or minimize these potential impacts. Specifically, routing engineers consider the following:
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Electrical feasibility. The placement of a new transmission line and substation must work electrically with the existing transmission system. To meet industry standards, system planners determine which existing transmission lines the new line cannot be placed immediately next to, such as existing 500-kV lines or certain smaller 230-kV lines.
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Existing corridors. The engineers look to see if BPA or other utilities have any existing corridors with vacant right-of-way or whether a new line could parallel another existing or proposed line, facility or road.
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Existing roads. If existing roads can provide access for construction and maintenance, impacts can be reduced.
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Houses and other structures. Existing homes, schools, businesses, historical structures or areas of cultural importance are avoided if possible.
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Existing land uses. In addition to the existing houses and structures, land use is an important consideration. Engineers try to find compatible land uses such as industrial land and some agricultural and timber lands while trying to minimize impacts to residential land, parks and any special districts or areas of local or regional interest.
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Terrain. If a new line can follow or parallel ridge tops, it could avoid crossing steep sided valleys and minimize new road impacts.
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Visual impacts. The size of transmission towers and the potential need to clear trees and develop new roads can increase the visibility of a new line. Routing engineers consider locations where people would likely view the proposed line such as homes and roads, river crossings, parks and other recreation areas.
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Sensitive habitats. Engineers consider potential impacts to plants and animals and try to avoid wetlands, nesting sites, habitats of threatened and endangered species, and other sensitive locations wherever possible.
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Potential Erosion. Engineers try to avoid the potential for soil erosion and the impacts erosion could have on water quality by avoiding steep slopes, erosive soil types and even rocky areas if they would require blasting.
Developing Route Segments into Potential Alternatives
For this project, BPA has identified preliminary transmission line route segments. These route segments vary in length and are composed of existing and new rights-of-way. Some parallel existing rights-of-way. Route segments cross privately and publicly owned urban and rural lands. The route segments can be combined in various ways to form route alternatives for the proposed transmission line. BPA will use comments received during the scoping period, continuing discussions with various interested parties and further transmission line design work to develop route segments into transmission line alternatives to be studied in the Draft EIS.
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I-5 Corridor Reinforcement Project