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DEVENS — As it moves toward a final method for measuring and enforcing noise standards for Evergreen Solar, the Devens Enterprise Commission has reworked its measurement protocol and adopted a new compliance document.

According to the new protocol set at the board’s July 8 meeting, noise readings will be taken from two monitors at 20-minute intervals, 24 hours a day, 7 days a week.

One monitor is located beside a set of volatile organic compound air filters and the other beside a block of nine massive elevated cooling towers. Maximum readings allowed at the air filters will be 60 decibels during the day and 58 decibels at night. Maximum readings at the cooling towers will be 55 decibels during the day and 52 at night.

The revision calls for an across-the-board 5-decibel drop in acceptable noise levels from the existing protocol.

“The idea behind this lower limit was to make things simpler,” said Michael Lannan of TechEnvironmental.

According to the new compliance policy, written notices of noncomplaince must be filed with the commission, which will trigger a demand for monitoring data.

The policy will presume Evergreen is the source of the sound unless the commission determines that Evergreen did not cause the noise or that its source was one of the exceptions to Devens Industrial Standards, such as an outdoor event or construction activity.

Jay Wallace, co-owner of Dunroven Farm at 62 Old Mill Road in Harvard, lobbied for 5-minute readings to continue, arguing that removing them would be a mistake.

Phil McRae, Evergreen facilities manager, said 5-minute readings had been taken only for diagnostic purposes. High noise levels trigger alarms, he said, and an employee performs an inspection of exterior systems in “under 30 seconds.”

Commissioner John Oelfke said the protocol still fails to address how to segregate Evergreen noise.

“Evergreen is again in a position of having to prove something not to be true,” he said.

Last summer, Evergreen contended that other sources — from crickets at night to repaving along Route 2 in Harvard, and Pan Am Railway’s intermodal train-to-truck facility on Barnum Road — contributed to the problem.

“We’re back to where we were a year ago, except we have a lower standard,” Oelfke said.

Chairman Bill Marshall disagreed, noting that the monitors are located beside the two most suspect pieces of external equipment.

“Unless you have a plane or helicopter landing in their parking lot or whatever, then probably something is happening at Evergreen Solar that they’d have to address,” he said.

Wallace also challenged the decision to give Evergreen 90 days to comply with the new protocol, saying that misses the summer window when high temperatures trigger added demand from the cooling towers. He also called for a “worst case scenario” sound test with the plant’s equipment operating at full tilt.

“We believe we’ve given up some of our rights,” Evergreen Chief Financial Officer Michael El-Hillow shot back. “That was part of the good faith approach.”

He argued that the recent heat wave offered a worst-case test, with no complaints logged.

“Whatever it’s worth, Jay … we’ve done the test,” he said

Commission Planner Neil Angus said there was “no need for a worst-case stress test,” noting that overage would spark demand for further remedy or “we’ll have to take necessary actions.”

Attorney Michael Giaimo, representing Charles and Janice Perry of Old Mill Road in Harvard, called for public access to the monitoring data.

Lannan countered that the point of the new compliance policy, which calls for filing complaints with the commission, was to simplify the procedure.

“The point now is that they just log this data,” he said. “When you call and complain, that’s the issue and that’s when the data will be available.”

El-Hillow told the Perrys to “just call” if they want the data.

“We did,” Janice Perry said.

“We’ll get it to you as fast as we can,” El-Hillow said.

“It’s been since June 14,” said Perry.

“If we made a mistake we’re sorry,” El Hill said. “We’d be happy to give you the information.”

The commission continued the meeting to Monday, July 19, at 7:30 a.m., to allow time to incoporate changes raised at the July 8 session.

Meanwhile, El-Hillow said, “we’re designing the second wall. We’ve ordered materials. We’re moving forward.”

A suggestion by the Peter Lowitt, the commissions administrative director, that it find Evergreen in compliance with low-end frequency noises was shelved until the next meeting.