The ambient noise degradation rule stated that a new source of noise could not raise background noise by more than ten decibels near residences. But a single wind turbine is generally not a single point source of noise pollution, Gravitt says. The wind has a background noise that changes as wind speed increases. The rule failed to recognise these characteristics, as FPL Energy found when building its 300 MW Stateline Energy Center on the Oregon and Washington border four years ago. FPL's Ann Walsh says the company found that Oregon's noise regulation was the most difficult in the nation before the new rule was adopted. A landowner who had a rental residence near turbines had to ensure the home was vacated before the project was built, even though the tenant wanted to continue living there.
The new rule gives the resident an option to stay or leave. It allows the property owner to remain in the residence by waiving the ten decibel rule, as long as the maximum noise level is not greater than 50 decibels. Industrial point sources of noise pollution, such as natural gas turbines, are allowed a maximum of 36 decibels.
Several wind projects in Oregon can now move forward, says Mark Berstasch, an acoustical engineer with CH2M Hill in Portland. Oregon already has 261 MW of installed wind capacity. "It comes down to setback distances -- how far a residence is from the wind turbine," he says. "In Oregon, if a resident is a willing participant and is willing to accept a higher noise level, the turbine can be placed nearer their home." He insists the rule is not special treatment for wind projects, but recognition that noise from wind turbines is dependent on and varies with wind speed.
Not all agree with him. In the hearing process others warned that the looser standards and landowner choice could lead to adverse environmental and health impacts and said wind facilities should not be given special treatment.