DOE/EIS-0332; McNary-John Day Transmission Line Project Draft ...

BPA McNary-John Day Transmission Project
Draft EIS
February 2002
Wildlife
the total regional population (Willdan Associates 1982). A bald eagle was found under
the lines near the McNary Dam, suggesting it struck power lines.
When there are multiple lines within a corridor, birds are more likely to strike a
conductor (wire) if the conductor heights vary. Multiple conductors at different heights
creates a “fence” effect, a larger area in which the bird most avoid. The proposed line
would add to an existing fence effect. The existing 230-kV and 345-kV towers are
80 feet and 110 feet tall respectively, and have a flat configuration (the three conductors
on the towers are strung at the same height). In areas where there is an existing 500-kV
line, the towers are about 180 feet tall and the conductors are stacked (various heights).
For the proposed line, the towers would be about 145 feet tall, and the conductors would
have a delta configuration (one conductor higher than the other two). Please see
Chapter 2, Figure 2-2 for tower configurations. Birds tend to be more likely to strike
ground wires. Ground wires are much smaller in diameter than conductors and span the
top of the tower to protect the line from lightning strikes. The existing lines in the
corridor have ground wires for a mile on either side of the Horse Heaven Substation west
of Paterson. The proposed line would have two ground wires the length of the line.
These ground wires would increase the fence effect and contribute to potential bird
strikes. Please see Chapter 2, Figure 2-3 for the location of the ground wires on the
tower.
Amount of Use
In general, the more birds that fly in an area, the greater the risk of collisions with power
lines. The areas of highest concern are where lines span bird flight paths, including river
valleys, wetland areas, lakes and narrow corridors such as passes that connect two
valleys. Transmission lines between waterfowl feeding and roosting areas would also be
hazardous to waterbirds (McNeil 1983).
The proposed line would cross few areas of open water or wetlands and would run
primarily through upland grazed shrub-steppe and croplands. One area of high seasonal
bird use is the Umatilla National Wildlife Refuge, located between 0.1 and 4 miles south
of the project vicinity between corridor miles 11 and 28. Waterfowl use the area during
the fall and typically fly from the Toppenish Creek area to the north (Haines pers.
comm.) as well as from other locations (Browers pers. comm.). This area would
represent the highest risk areas for avian collisions because of the high seasonal use and
the species involved.
Other areas of potential collision risk would occur where lines cross center pivot
irrigation circles planted with corn to attract waterfowl and located north of the Umatilla
National Wildlife Refuge, near Crowe Butte Park, and at the Rock Creek and the
Columbia River crossing, particularly at McNary Dam. Waterfowl and raptors flying up
the Columbia River may strike the lines crossing the Columbia River. A portion of the
proposed transmission line would be located between open water loafing areas on the
Columbia River and the center pivot irrigation-feeding habitat. As a result, some
additional mortality would be expected to occur in that vicinity.
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