September 2, 2009

Sewage exacerbates low oxygen in south Hood Canal, scientists say

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After three years of studies, including “complex computer models,” scientists for Washington’s Hood Canal have concluded that septic systems discharging waste into the the lower arm of the canal are likely the cause for dropping oxygen levels, writes Christopher Dunagan in the Kitsap Sun.

The Hood Canal Dissolved Oxygen Program has been seeking to remove the Hood Canal from Washington’s “impaired waters” list, specifically by addressing exceedingly low levels of oxygen in the waterway, which can have detrimental effects on marine wildlife. While the proposed “action plan” to decrease nitrogen levels notes a variety of pollution sources, human waste makes up one tenth of the nitrogen in the lower Hood Canal. One of the proposed remedies is to replace current septic systems with ones that discharge the waste into forests instead.

The debate over whether septic systems are to blame for depleting Hood Canal’s oxygen levels is a long one, and one that InvestigateWest’s own Robert McClure has covered. A 2008 Seattle Times article found that currents entering Hood Canal from the ocean are the largest source of nitrogen to the canal. Nitrogen-releasing alder trees, which are prolific in the area due to heavy logging, also overshadow nitrogen levels released by human activity.

While the final report on the Hood Canal research is not due until next year, initial findings will be presented Sept. 16. Meanwhile, construction on a $40 million sewage-treatment plant is scheduled for fall.

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