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DEVENS — Devens Enterprise Commission administrator Peter Lowitt confirmed that a noise-study report on the Evergreen Solar facility, produced by DEC’s consultant but funded by the company, was submitted June 1.

But Lowitt says the release of the data to the public would occur “late Wednesday” on the DEC’s Web site (http://www.devensec.com/news.html) to allow for “number crunching” to be done first.

The report’s arrival comes after months loud noise coming from the rear of the Barnum Road solar panel manufacturing plant. Several homeowners on Old Mill Road in neighboring Harvard have complained of an irritating, unnerving sea of sounds traveling up through the woods from the plant and into their backyards, in a sort of amphitheater, amplifying effect.

The weeklong study was spearheaded by sound technician Doug Sheadel of Specialties in Westford.

Touring the plant

Plant manager Craig Core provided The Public Spirit with a tour of the Evergreen Solar plant May 29. He explained that while the plant opened in July 2008, small-scale production of solar panels began shortly thereafter in August 2008, which marked the Phase-I launch of Evergreen Solar’s production plan. However, noise complaints roughly coincide with the start of Phase II in January of this year, when the plant’s air-scrubbing system went online.

Silver-gleaming machinery stands several stories high in fenced-off clusters behind the enormous 500,000-square-foot manufacturing plant. Most imposing is a series of chimney-like stacks, approximately four stories high that serve as the end of an air-purification system. Air leaving the plant is scrubbed of impurities like airborne silicate particles or acid vapors by “raining” water down over the air to knock out and contain the solids before the remaining cleansed air is released into the atmosphere.

A series of powerful fans “blow and pull air out of the plant,” said Core. The fans were targeted early on as having defective blades that caused one type of offending noise. But despite the fan fix, several different sounds persist.

Next, Core described the series of massive cooling towers topping approximately three stories from ground level. The enormous air-conditioning units maintain plant temperature and humidity for the delicate manufacturing process. But Core said in an attempt to tamp down noise, the plant is running only the units closest to the plant and opting not to use the outer row of cooling towers directly facing the neighbors’ properties.

The hope is that by only using the units closest to the plant, the outer units can serve as an added sound buffer for the operating units. Core explains the plant was designed to never need the full use of all the cooling towers at the same time.

“Different people have different sensitivities,” said Core. He said the company fully supported and financed the DEC sound study that captured graphic readings of the various sounds originating from the plant. The three monitoring devices, placed as far away as a quarter mile and a half mile from the plant, also recorded times and severity of noises that will now need to be matched with the plant’s operation schedule to tie together possible sound sources.

Neighbors’ complaints can clearly be traced back to several events, like sirens that blared when plant doors opened in the rear of the plant. Core said that siren noise has been eliminated. Another bone of contention has been the daily gas deliveries. Despite promising to restrict gas deliveries from 8 a.m. to 4 p.m., a PraxAir tanker breached the peace on May 21 with an early morning gas delivery between 5 and 6 a.m., prompting the issuance of a second Evergreen Solar noise violation notice from the DEC. The second violation for the fledging plant came less than two months after its first noise violation issued April 1.

The solution? Core says the company resorted to manually locking the chain-link fence surrounding the plant’s massive argon and liquid nitrogen gas tanks, denying access to PraxAir for anything but business-hour deliveries.

Presently, the gas is extracted from the tanker and pumped into the storage tanks by the tanker truck’s onboard pumping system that is extremely noisy. In Core’s report to the DEC on Monday, he wrote “to wrap acoustical insulation around the truck mounted pumps failed,” but that the gas company is working with Evergreen to work on some kind of temporary mitigation system, like the “installation of ground- mounted pumps with acoustic insulation that would be used to pump liquified gas from the delivery truck to the storage tanks.”

“Today the pumps are located on the trucks and cannot be sufficiently quieted. Lead times are quoted at eight to 10 weeks for installation of the new pumps,” wrote Core. But he also confirmed during the plant tour that at an estimated cost of $100,000 each, Evergreen Solar wants to ensure the fix is the right one for the problem.

Neighbors wait

Jay Wallace, co-owner of neighboring Dunroven Farm on Old Mill Road in Harvard, commented on Tuesday that the new gas-delivery time restrictions appear to be working. But, on the down side, “there is a new tone that has either been added to the mix or has replaced the noise generated by the filling of the gas tanks. At this point we do not know which it is. If it is the latter, then it indicates that Evergreen is trying to make changes. However, I cannot characterize these changes as improvements.”

Wallace was provided a sound meter by the DEC sound consultant to take readings during times of great noise production, and on Tuesday, the offending noises continued. “The reading during the period the noise was being generated was 55.9dB to 57.5dB. They are supposed to be at 38dB,” explained Wallace, “Each 10dB increase is roughly a doubling of the sound, so at 48 dB the sound is twice as loud as it should be, at 58 it is four times as loud and at 68 it is eight times as loud,” he explained.

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