Dissolved Oxygen: In my own words

by Dr. John H. Brunke, PE

First let me say the fecal coliform issue at Freeland Park is completely a separate issue from the dissolved oxygen water quality issue in Holmes Harbor.

Water, just like air, contains oxygen. Just as we breathe air, fish pass water through their gills removing oxygen. This oxygen, referred to as dissolved oxygen (or DO) also enters the water by contact with air and from water plants which consume carbon dioxide and produces oxygen. The most common plant is algae. Although algae produces oxygen when growing, when it dies it sinks to the bottom to decompose. This decomposition process consumes oxygen.

The growth of algae depends upon a number of factors, one is the available nutrients in the water to promote growth. Sources of these chemicals (nitrates and phosphates) include lawn and agricultural fertilizers and other surface water runoff, outfalls of older (most) sewer systems, and in some cases, ground water contaminated by septic systems.

Holmes Harbor, as do many waters in Puget Sound, has an adverse classification due to low dissolved oxygen. Penn Cove, home of the mussel farms, has the same DO rating. Other waters include Hoods Canal, Saratoga Passage and Possession Sound.

The question is: will providing sewers and replacing a small fraction of the septic systems lining the 17 miles of shores of Holmes Harbor change this rating? The answer is no. Until the MANY sources of nutrients in Puget Sound are all addressed the situation will remain. With no plan to do this, the issue of placing the burden upon a few property owners, with no positive result, is unacceptable.