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DEVENS — The Devens Enterprise Commission voted unanimously Tuesday to give Evergreen Solar Inc. a clean bill of health in terms of noise levels emanating from the Barnum Road solar panel factory.

The company has installed new sound-muffling walls in an effort to deaden the noise that had irritated neighbors over the past 18 months.

Commissioners specifically opted to nix a sound monitor it previously required the company maintain near the Harvard line. Instead, Mark Wallace of TechEnvironmental told the board that it agreed in July to require just two permanent sound monitors — one located aside air scrubbers and another aside a bank of air cooling towers.

Gone is the need to close the plant after five days of noncompliance because “real-time data” collection now sparks alarms and inspections to “go out and find the source of a sound increase.”

To violate the Devens noise limits with the wall and safeguards in place, “it would have to be a catastrophic failure. It’s pretty quiet back there,” said Wallace.

But those words didn’t reverberate with several Harvard residents who have attended commission meetings over the sound situation for the past year and a half.

Jay Wallace (no relation to Mark Wallace) said he has lost faith in the commission’s effectiveness in policing Evergreen.

“The track record of the staff and its advisers as to what we need and don’t need is abysmal,” said Jay Wallace, who is co-owner of Dunroven Farm on Old Mill Road. He blasted the commission for disregarding what he said was a three-way accord signed by the town of Harvard, the commission and former Evergreen CEO Richard Feldt. That resolution called for the maintenance of permanent Devens boundary sound-monitoring and a pledge to shut down the plant for sound violations that linger beyond five days.

“This process has been an unbelievable failure,” Jay Wallace continued. “This has taken 600 days. It should have taken 60 days.”

He said of lot-line sound readings: “It’s your regulation that calls out the property-line measurement. Not mine, yours.”

The Harvard Board of Selectmen doesn’t feel the conditions have been eliminated,” said Jay Wallace of the resolution.

Commissioner John Olfeke disagreed that Harvard was ever a signatory to the agreement.

“This is a DEC resolution, period,” he said.

Commissioner James DeZutter said with several incarnations of agreements enacted over the last year and a half, conflict has arisen over competing language.

“I don’t like that because if that happens, subsequently you’re going to have something here that disputes what this says, and then you’re going to go back on this whole thing, ad nauseum,” he said. “We move on, move forward. If there’s a problem, we’ll have to deal with it then.”

Evergreen, based in Marlboro, employs more than 800 people at the Devens manufacturing plant.