Birch Stream isn’t much to look at. The Bangor waterway snakes its way through culverts and under parking lots before dumping into Kenduskeag Stream. No one paid much attention to the glorified drainage ditch until it developed an overpowering odor this winter. Nearby residents complained of headaches and other ailments from the sickeningly sweet aroma.

It turns out the stream was the repository of an airplane de-icing chemical used at Bangor International Airport and the Maine Air National Guard base. Although the chemical, propylene glycol, a less toxic relative of antifreeze, had run off into the stream for years, an increase in air traffic at the military base had overburdened the narrow waterway. Because of post-Sept. 11 security measures and the war with Iraq, the amount of de-icer used at the Bangor airport complex tripled in two years to 150,000 gallons a year.

All this de-icer discolored the stream and gave it a terrible odor. State and local officials are still looking into the possible human health effects of the chemical and its impacts on the stream ecosystem. In the meantime, both BIA and the guard base have pledged to keep the propylene glycol out of the stream in the future.

The National Guard has said it will have a collection system for the de-icer in place by next winter. Since it is the bigger contributor to the problem, that is good news. BIA officials said it will take them a couple years to reconstruct a portion of the tarmac for airplane de-icing and to install the necessary piping to collect the liquid and divert it to the city’s wastewater treatment facility. In the meantime, it will set aside an area and corral the runoff with dikes. The permanent fix will take time because BIA is seeking federal funding for the project, an area where the state’s congressional delegation can be of help.

While keeping the chemical out of the stream is a good thing, officials at the base and commercial airport should also look for ways to reduce the use of propylene glycol. Many airports around the world have found ways to use less of the chemical, to better control its runoff and are looking for non-chemical alternatives. Bangor should join these efforts.

In the meantime, now that Birch Stream has been discovered, it should continue to receive attention. De-icer isn’t the only thing fouling the stream. Getting rid of the grocery carts and garbage strewn into the water would also be a help.