BANGOR – Work is nearly complete at the Maine Air National Guard base on a new holding system that is designed to nearly eliminate leakage of deicing fluid into the environment.

Made up of interlocking concrete tanks, the underground system can hold up to 150,000 gallons of the fluid before it is sent to the city’s wastewater treatment plant, Col. Craig Snow of the Air Guard said Wednesday.

Already 95 percent complete, the system should be up and running by Dec. 15 after some final plumbing and electrical work is completed, he said.

The $700,000 system, all federally funded, will replace the existing deicing fluid storage operation, in which the fluid is held in a 100,000-gallon open holding pond before being sent to the treatment plant.

“We’re certainly doing the best we can,” Snow said. “We believe in protecting the environment.”

Local concerns about deicing fluid from both the Guard base and Bangor International Airport began in 2003, when residents of Griffin Park, a city-owned apartment complex along Birch Stream, complained of illness they believed was linked to pollution of the stream.

Since BIA was built more than 50 years ago, rainwater that runs off the facility’s miles of pavement was piped into Birch Stream, a small tributary of Kenduskeag Stream that in turn runs into the Penobscot River.

The city and BIA in 2003 installed a new system that included a designated deicing area and a network of pipes and valves to capture deicer runoff and direct it to the city’s wastewater treatment plant. The Guard concurrently built the holding pond system it will replace in December.

The deicing fluid is made up primarily of propylene glycol, a biodegradable antifreeze often found in shampoo, soaps and even used in food as a sweetener, Lt. Col. Eric Johns, environmental manager for the 101st Air Refueling Wing, said Wednesday.

The antifreeze caused problems in Birch Stream because of its high oxygen demand, which reduced the oxygen available to aquatic organisms, he said.

“It consumes the oxygen in the stream,” he said.

The Guard’s new containment system – almost identical to the airport’s system – became necessary in 2004 when the treatment plant became overloaded with deicer, even when the fluid was sent from the pond in smaller batches of 10,000 to 20,000 gallons, Johns said.

With the new system, the fluid can be sent 24 hours a day in a steadier flow, he said.

Last winter, the Guard paid $9,000 to the city to treat the deicing fluid, down from $20,000 in 2003, Johns said. The fluid itself costs $4 to $8 a gallon, he said.

One way to cut down on the fluid’s use is to reschedule training operations to times when the sun is out or to occasionally house aircraft in hangars to protect them from the elements, Snow said.

The Guard also sometimes uses a vacuum to suck up smaller amounts of the fluid before it reaches the drain, he said.

“The first goal that we have is to minimize the use of deicing fluid,” Snow said.

Sometimes deicing is necessary, however, to keep critical operations running smoothly, such as when precipitation accumulates to more than 1/8-inch thick on an aircraft.

The buildup can change the aerodynamic contour of a wing, leading to potentially dangerous complications, Johns said.

“Basically, you’re changing the shape of the wing,” he said.