Environmental Engineering Reference
In-Depth Information
wire or structure, or another energized wire, so the electricity stays in the line. Larger birds,
however, such as the California condor, which has a wingspan of up to 9.5 feet, are more
likely to touch a power line and ground wire, another energized wire, or a pole at the same
time, giving electricity a path to the ground. In both situations, the birds are electrocuted
and killed, a fuse is blown, power fails, and everyone is impacted.
Birds also fly into power lines. It is generally believed that birds collide with power
lines because the lines are invisible to them or because they do not see the line before it is
too late to avoid it. Birds' limited ability to judge distance makes power lines especially
difficult to see, even as they are flying closer to them. Large birds are especially vulner-
able because they are not always quick enough to change their direction before it is too
late. Poor weather conditions, such as fog, rain or snow, as well as darkness, may make
the lines even more difficult to see.
When birds collide with power lines they are either killed outright by the impact
or injured by contact with electrical lines, resulting in crippling is likely fatal.
Electrocutions can also start wildfires and cause power outages. An estimated 5 to 15% of
all power outages can be attributed to bird collisions, with power lines (USFWS, 2005).
In addition to increasing wildlife mortality due to collisions and electrocutions, as well
as by serving as perches for predators, transmission lines can fragment and interfere with
wildlife habitats and corridors (WGA, 2009). Again, there are also concerns about the
visual impacts of transmission lines. Moreover, many people feel that living or working
near transmissions lines is hazardous to health. Burying transmission lines can help avoid
many of the environmental and aesthetic issues, but burying lines may also have negative
impacts on soil, vegetation, and other resources (Molburg et al., 2007), and underground
lines are typically four times as expensive as overhead lines (Brown and Sedano, 2004).
Also, although high-voltage direct-current (DC) lines can be buried, there is a limit on the
maximum voltage and length of alternating-current (AC) lines that can be buried.
In all, constructing major new transmission infrastructure can require 7 to 10
years from planning to operation: 1 year for final engineering, 1 to 2 years for con-
struction, and the rest of the time for planning and permitting. Substantial time and
controversy are added to the process when environmental and related concerns are
addressed at the end instead of at the beginning. The specific environmental impact
concerns are addressed in the following sections.
s
oCioeConoMiCs
Direct impacts would include the creation of new jobs for workers (approximately
two workers per megawatt) at wind energy development projects and the associ-
ated income and taxes paid. Indirect impacts would occur as a result of the new
economic development and would include new jobs at businesses that support the
expanded workforce or provide project materials and the associated income taxes.
Wind energy development activities could also potentially affect property value,
either positively from increased employment effects or the image of clean energy or
negatively from proximity to the wind farm and any associated or perceived envi-
ronmental effect (noise, visual, etc.). Adverse impacts could occur if a large migrant
workforce, culturally different from the local indigenous group, is brought in during
construction. This influx of migrant workers could strain the existing community
infrastructure and social services.
