Setting wind turbine noise threshold proves tricky 

EASTHAM – During these summer nights, even in the quietest locations in town, the sound of chirping insects can be heard. To some, this is a soothing rural sound to hear while falling asleep. For others, accustomed to busier environments, it doesn’t provide enough sound to peacefully drift off.

In short, “noise” is subjective.

That’s one reason it’s proving so difficult for the ad hoc committee charged with developing a commercial wind turbine zoning bylaw to nail down a threshold for noise. In its continued efforts to craft a zoning bylaw that addresses the best interest of the town with regards to commercial wind turbines, the ad hoc committee is currently ironing out the section of the proposed bylaw addressing the allowable decibels of noise a wind turbine can produce over the ambient sound level.

In a typical wind turbine zoning bylaw, including the model created by the Mass. Div. of Energy Resources, the decibel levels produced by a turbine are measured at “the property line and at the nearest inhabited residence.” The DOER bylaw allows for wind turbines to produce noise up to 10 decibels (dB) above ambient noise.

While all geographic areas are unique, The Engineering Tool- Box states that typically outdoor ambient noise levels (on the dBA scale, which is closest to the human ear) in a wilderness area can be as low as 30 to 40 dBA, and in an urban area can be as high as 85 to 90 dBA. It states most urban dwellers live with ambient noise of more than 48 dBA. Ambient noise also differs between day and night, as well as through the seasons.

Since last November, ongoing noise testing has been done with funding from the Massachusetts Technology Collaborative on the town-owned land off Nauset Road where the former, selectmen-endorsed proposed bylaw intended wind turbines to be erected. One reason for the lengthy testing is to determine ambient sound levels during all four seasons, with and without foliage, etc. At its last meeting Monday night, the board of selectmen discussed whether or not these tests should continue given that the new proposed zoning bylaw is not site specific. Ultimately with a four to one vote, with Selectman Carol Martin voting against continuing the test, it was decided that the testing should go on.

The next day, at the ad hoc committee’s regular meeting, Andrew Wells, who worked on the alternative wind turbine bylaw with Philip Hesse, felt the selectmen’s vote ran counter to the charge of the ad hoc committee to create a site-neutral bylaw that would be applied to specific sites.

“What happened last night was a reaffirmation of an original decision to proceed with a site specific plan,” Wells said.

Committee members who addressed the issue at the Aug. 21 meeting felt the favorable vote to continue testing stemmed from the fact that it’s fully funded by the MTC and costs the town nothing, so what harm can it do?

The matter did raise many other issues regarding testing, including a decision by the committee to require noise testing in the bylaw, and Wells went as far as to open the door to setting the parameters of these required tests. The committee agreed that testing must be site-specific due to the number of variables in each unique area, therefore testing in one area was not applicable to another.

While still in draft form, the current wording in the proposed zoning bylaw leans towards a 3 to 5 dB limit over normal ambient sound for wind turbines, which may or may not rule out all available technology.

However, comments made by energy committee representative Joe Mistretta signaled a possible move in a new direction in the zoning bylaw to differentiate between residential and commercially zoned land. Mistretta recognizes that “a very restrictive set of standards” is being created for residential areas, but in his opinion, this is “overly restrictive” for commercially zoned sites.

At the Tuesday meeting, committee chair Tom Reilly also relayed news from Town Administrator Sheila Vanderhoef that the Oct. 31 deadline for a draft bylaw is flexible; however, no comment was made by the committee as to whether it would need more time.

By Derek Burritt

The Provincetown Banner

23 August 2007

Source: Eastham Wind Truth