Oil and Gas at Your Door? (2005 Edition) - Earthworks

IMPACTS ASSOCIATED WITH OIL AND GAS
Organization, outdoor sound that exceeds 55 dB begins to be a nuisance to people. 218 During
the nighttime hours (10 p.m. to 7 a.m.), sound levels in rural or quiet suburban areas are often
as low as 25 to 35 dBA, 219 while urban areas may be 80 dB or more. 220
Oil and Gas Development Noise
In a La Plata County, Colorado study 221 noise levels were reported for a number of oil and gas activities
and equipment:
• A typical compressor station: 50 dBA* at 375 feet from the property boundary (noise emitted 24-
hours-a-day)
• Pumping units: 50 dBA at 325 feet from the well pad (noise emitted 24-hours-a-day)
• Fuel and water trucks: 88 dBA at 50 feet; 68 dBA at 500 feet
• Crane (used to hoist rigging equipment): 88 dBA at 50 feet; 68 dBA at 500 feet
• Concrete pump (used during drilling): 82 dBA at 50 feet; 62 dBA at 500 feet
• Average well construction site: 85 dBA at 50 feet; 65 dBA at 500 feet
*Often, equipment used to measure sound is designed to account for sensitivity of human hearing to
various frequencies. This is known as A-weighted correction, and the measurement is an A-weighted
decibel (dBA). 222
How Sound Travels—Sound is caused by changes in air pressure. For example, when a mallet
strikes a drum the drumhead begins to move back and forth (vibrate). As the drumhead moves
down, air is pulled toward it, and as the head bounces back up it pushes air away. This creates
changes in air pressure that move (or propagate) away from the drum, eventually striking our
eardrum. These changes in pressure are known as sound waves.
There are a number of factors that affect the propagation of sound. The most important
include: distance from source; obstacles such as barriers and buildings; atmospheric absorption;
wind direction and speed; temperature and temperature gradient; humidity; precipitation;
reflections; and ground absorption. 223
It is important to understand that noise does not always decrease as one moves away from a
noise source. The above factors can work to increase or decrease noise levels. For example, at
short distances (up to 160 feet) the wind has a minor influence on the measured sound level.
At distances greater than 1,000 feet from a noise source, noise can become louder on the
downwind side by as much as 20 dB, while on the upwind side levels can drop by 20 dB
(depending on wind speed and distance). 224
Other things to consider include the fact that while barriers may act to reduce high frequency
sounds, low frequency sounds are difficult to reduce using obstacles or barriers. Additionally,
while soft ground surfaces and the atmosphere are effective at absorbing mid-frequency and
high frequency noise, these factors do not tend to reduce low frequency noise to the same
degree. This means that as one moves away from the source, low frequencies often become
much more prominent. 225
Prolonged periods
of noise exposure to
65 dBA can cause
mental and bodily
fatigue.
What Makes Certain Sounds Annoying?—Whether a noise is objectionable will vary depending
on its type (tonal, impulsive, etc.), the circumstances (e.g., does the noise occur in an area
where there are already loud noises versus a quiet rural setting), and the sensitivity of the indi-
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