Friends of Sebago Lake: Scientific Proof that Stopping Pollution and Removing Dams Fixes Rivers: Lower Presumpscot River now meets Class A standards.

By Douglas Watts
Friends of Sebago Lake

Until 1999, the Presumpscot River near Portland, Maine was perhaps the filthiest and most polluted river in New England. Then two things happened. First, in July 1999 the S.D. Warren Paper Company shut down its paper pulp making operation in Westbrook, Maine, removing a giant gob of organic pollution from the river. Then, in 2002, the head of tide Smelt Hill Dam was removed. This dam, built in the early 1900s, created a seven mile long stagnant pond which allowed the paper mill pollution from S.D. Warren to fester and settle in the river and consume most of its dissolved oxygen.

The first underwater photos ever taken of native blueback herring

and American shad (the big fish) ascending Presumpscot Falls,

Presumpscot River, Portland, Maine. June 6, 2009.

This is the falls they were swimming up through.

In Sept. 2008, the Maine Dept. of Environmental Protection (DEP) and U.S. Environmental Protection Agency (EPA) conducted an in-depth study of the Presumpscot River to determine how the river has responded to these two events. The full results of the study, authored by Donald Albert, P.E. of the Maine DEP, have recently been compiled and published. A PDF copy is here.

The report's findings are quite astounding. Prior to 1999, the Presumpscot could barely meet Maine's Class C water quality standards, which require 5 parts per million (ppm) of dissolved oxygen in the water at all times. The 2008 study found that what had been the most polluted reach of the river, below the S.D. Warren paper mill in Westbrook, now easily attains 7 parts per million of dissolved oxygen, even under high temperature, low-flow conditions. This means the lower Presumpscot River is now in full attainment of the dissolved oxygen standard of Maine's highest water quality classification, Class A, which requires 7 ppm of dissolved oxygen at all times. The study report states at 8:

"Early morning dissolved oxygen (DO) readings on the Presumpscot are compared to the minimum class C criteria of 5 ppm. In all cases, criteria are easily met and always exceeded 7.0 ppm."

It might seem at first glance that the difference between 5 ppm and 7 ppm of dissolved oxygen is not a big improvement or a big deal, but it is. Dissolved oxygen standards were created under the Clean Water Act and Maine law because they accurately determine what and how many aquatic organisms, including fish, can inhabit a river. Even in the most clean rivers and streams, the upper limit of dissolved oxygen levels is around 10 ppm, so it's a fairly narrow window, and native critters of Maine rivers have evolved to live in waters with 7-9 ppm. Dissolved oxygen levels above 7 ppm allow all of Maine's aquatic life to happily inhabit a river and reach their fullest potential. When dissolved oxygen levels fall below 7 ppm that aquatic life, oxygen-intensive aquatic animals like ...

native brook trout ...

Atlantic salmon ...

and stoneflies ....

... start to suffer and eventually disappear. Any aquatic biologist in Maine will tell you that while Maine's Class C standards require at least 5 ppm of dissolved oxygen, this is far from optimal, sort of like saying that technically a prisoner can live on bread and water ... for awhile ...

Here is a story from 1999 about the first, fledgling efforts to rescue the Presumpscot River from continued oblivion.

During the 1960s, 1970s and 1980s, very few people, including scientists, ever believed the Presumpscot River would attain Class A water quality during their lifetimes. During this period and in the decades prior, most people in southern Maine, and those who lived along the Presumpscot, had long given up hope that the Presumpscot River would ever be clean again. The challenge seemed too daunting and the prospect too remote. What then seemed a fantasy is now the reality. It has been done. It can be done.