Most of the Androscoggin River meets Class C water quality standards or better. Class C is the lowest standard and means the water is deemed fishable and swimmable. The river even meets Class B standards near the New Hampshire border.

The biggest area of the Androscoggin that is below Class C standards involves sections of the 14.5 mile Gulf Island Pond. The pond runs from Lewiston-Auburn up to Turner, Greene and Leeds. The Livermore Falls impoundment also fails to meet Class C.

Gulf Island Pond does not meet standards in the summer for two reasons: a lack of oxygen in the water and algae blooms.

The substances that eat up oxygen, degrade water quality and prompt blooms are essentially organic waste left over from the papermaking process and phosphorus.

“Paper mills located in Berlin, N.H., Rumford and Jay are the major source of most of the pollutants (in Gulf Island Pond),” according to the Maine Department of Environmental Protection’s Web site. Other smaller point sources for the pond’s pollution are the municipalities of Berlin, Gorham, Rumford-Mexico and Livermore.

Sections of the river below the pond, including the Lewiston-Auburn stretch, meet Class C standards except after heavy storms, according to the DEP.

During heavy rain, too much water goes into street drains. Stormwater mixes with sewage and overflows into the river at the cities’ treatment plant. When that happens, part of the river downstream from the plant temporarily does not meet Class C standards.