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

BPA McNary-John Day Transmission Project
Draft EIS
February 2002
Public Health and Safety
transmission-line fields remains somewhat controversial. Magnetic fields are most in
question as possible sources of long-term effects, although studies sometimes lump the
two (electric and magnetic) fields together. In recent years, considerable research on
possible biological effects of electric and magnetic fields has been conducted. A review
of these studies and their implications for health related effects is provided in
Appendix G. In addition, the Department of Energy provides a booklet on this topic
(Questions and Answers about EMF). Scientific reviews of the research on EMF health
effects have found that there is insufficient evidence to conclude that EMF exposures
lead to long-term health effects. However, some uncertainties remain for childhood
exposures at levels above 4 mG.
An increase in public exposure to magnetic fields could occur if field levels increase and
if residences or other structures draw people to these areas. The predicted field levels are
only indicators of how the proposed project may affect the magnetic-field environment.
They are not measures of risk or impacts on health. The 79-mile-long corridors in which
the proposed line would be built is sparsely populated. There are about 40 structures
within 400 feet of either side of the right-of-way edge.
Bonneville has predicted the magnetic fields of the proposed and existing transmission
lines. The field levels from the existing and proposed lines change along the corridor,
depending on how many lines are in the corridor, where they are located relative to one
another, and the width of the right-of-way. For this project there are six different line
configurations (Configurations 1, 2, 3, 4, 4A, and 4B).
A majority of the proposed line magnetic field levels would be those shown for
Configuration 1 (see Figure 3-8), with an increase of about 12 mG at the edge of the
right-of-way on the north side. (The 12 mG value is for maximum current and minimum
line height above ground in the worst case scenario. The values would be less for
average current and with higher line heights above the ground.) The magnetic fields on
the south side of the right-of-way would not change. This configuration is in all the
locations where the proposed line would parallel the two existing lines on the north side.
Within this configuration there are about 13 structures (combination of residences and out
buildings) within 400 feet of the north edge of the right-of-way.
About 4 miles of the right-of-way are represented in Configuration 2 (see Figure 3-9),
with an increase of about 76 mG on the north edge of the right-of-way. The magnetic
fields on the south edge of the right-of-way would not change. This configuration would
be located where the Ashe-Slatt 500-kV line parallels the right-of-way (corridor miles 23
through 27). There are no homes or buildings on the north side of the right-of-way in this
area.
About 3 miles of the right-of-way would be represented in Configuration 3 (see
Figure 3-10), with an increase of about 76 mG on the south edge of the right-of-way and
16 mG on the north edge. This configuration would be located where the proposed line is
on the opposite side of the highway from the existing lines, corridor miles 65 through 67.
There are no residences or buildings in this area.
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