Document 28: Lake Washington Pollution

"Edmondson Announces Pollution May Ruin Lake," University of Washington Daily (13 October 1955).

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Edmondson Announces Pollution May Ruin Lake

Pollution might ruin Lake Washington for swimming and fishing, a University scientist said Tuesday.

Dr. W. Thomas Edmondson, associate professor of zoology, said there are evidences of change, probably caused by the increasing amounts of treated sewage the lake has received in the last 10 years.

While studying the lake last summer with the Pollution Control Commission, Dr. Edmondson and Dr. George C. Anderson, research associate in zoology, collected and analyzed samples of lake water.

Their study two symptoms of change. The first is that a species of algae that has caused trouble on other lakes appeared for the first time. In dense population, the algae would produce scum that would be thrown up on the beach and also would ruin the water for swimming. It was this algae that caused the reddish scum observed at the Gold Cup regatta, he said.

Oxygen Decreases
The other symptom of change was a decrease in oxygen in the lower, cold water. To be good for trout, the lake must have plenty of oxygen in the lower water, Dr. Edmondson explained. But with the greater production of life, more dead material settles to the lower levels during the summer. Bacteria on this algae uses up the oxygen, he said.

The scientist pointed out that neither of these developments is critical at the present time. But they are significant as evidence that the lake is in a transitional state because of sewage, he added.

Dr. Edmondson said that Lake Washington in its natural state is not a productive lake. With few salts dissolved in it, the water is soft. It remains clear throughout the summer.

Increasing Sewage
The increasing amounts of sewage emptied into it the last decade has released large quantities of nitrates and phosphates which are used by algae for nutrition, he explained.

“This has the same effect on life as fertilization has on a lawn,” he said. “It is one reason treated sewage has become a problem.”

Dr. Edmondson said that his professional interest in the changing nature of the lake is not so much the effect on recreation as the experience of observing and analyzing the transitional nature of the lake and of lake productivity.

Earlier in the century, lakes in Germany and Switzerland went through similar changes. Dr. Edmondson said, “It is our desire to add to the research that has been accomplished there.”

Center for the Study of the Pacific Northwest