OLD TOWN – Department of Environmental Protection employees were at the former Georgia-Pacific Corp. mill on Monday to test the plant’s biomass boiler system to see if problems under new owner Red Shield Environmental have been fixed.

Red Shield shut down its biomass boiler for most of last week to make repairs to its soot collection system. It restarted the boiler on Friday.

Soot from the facility fell onto homes and yards in neighboring Bradley on two occasions in the past few weeks, according to Red Shield and state environmental officials. Bradley is directly across the Penobscot River from the mill.

Red Shield, which is composed of a group of private investors, is using the biomass boiler to heat the facility and produce power to sell to the region’s power grid. It plans to produce ethanol at the site.

The company bought the mill last September, six months after G-P decided to close the plant.

Before the air emissions problems, Red Shield had been burning a mixture of construction and demolition debris and green wood chips.

“The DEP is going up this afternoon to test to see how the whole boiler system, but especially the ash handling and their [ash collection system] are working before we’ll even consider allowing them to burn [construction and demolition debris] again,” said Ed Logue, DEP eastern Maine regional manager, on Monday.

The boiler is permitted to burn up to 500 tons of fuel a day. Half of that fuel can be construction and demolition debris.

In what mill and DEP officials have said is a separate incident, ash samples collected from the boiler have tested positive for toxic levels of lead.

Logue explained that the toxic levels, which exceed DEP’s 5 milligrams per liter standard, have been found only in the test done to determine “how much lead will leach out of a sample under certain controlled laboratory situations.”

“The only thing that’s changed is this leaching lead level of whether it can be properly disposed of or not,” Logue said.

The amount of lead found in the raw construction and demolition debris, as well what comes out of the stacks, hasn’t changed since the original testing that was done when Red Shield first began to operate and the numbers were well within DEP’s limits.

The DEP has ordered Red Shield to stop burning construction and demolition debris until the issues can be fully investigated and resolved.

Wood waste is separated at sorting facilities to be used as fuel for companies such as Red Shield. Items such as metal, brick and treated wood are removed during the sorting.

The demolition debris is a cheaper fuel and is an alternative to disposing of it in Main’s limited landfill space.

“When you burn 50-50 it makes the cost of the fuel per ton quite a bit better,” Red Shield spokesman Dan Bird said Monday. “It does make it possible to do business.”

Some members of the public are concerned about using the debris as a fuel because it has the potential to contain pollutants such as lead and asbestos.

Some of the Red Shield ash with high lead levels appears to have been disposed of at the nearby Juniper Ridge Landfill, formerly the West Old Town Landfill.

The state-owned landfill is operated by Casella Waste Systems Inc., which is obligated through a contract with the state to provide Red Shield with construction and demolition debris fuel.

When Georgia-Pacific still was operating the mill, it never burned demolition debris.

“It was part of the reason they had the financial difficulty in doing business here,” Bird said. “We knew that first and foremost we had to lower the cost of energy to have any possibility of restarting the facility.”

Casella has stopped disposing of waste in the area of the landfill where the soot that’s believed to be toxic was dumped. It is illegal to dispose of toxic waste in Maine, and depending on DEP’s findings, Casella may have to remove the contaminated waste.

The original toxic level showed up in a sample taken from the boiler in February. DEP requires Red Shield to take periodic samples, which are sent to a lab for testing.

“They have done a number of repairs on site both in collection system and pollution control equipment,” Logue said.

DEP hasn’t made a decision as to when or if Red Shield will be able to begin burning construction and demolition debris again.

“Obviously, we have to resolve both the air issues and the solid waste issues before we make that decision,” Logue said.

He added that Environmental Protection Commissioner David Littell has said he will make the final call. “There’s still some ash sampling that needs to come back.”