subscribe to the Partnership Newsletter link

 

Back to Press Releases

MEDIA CONTACT
Katy Johansson
360.725.5442
katy.johansson@psp.wa.gov

Sandy Howard
360.407.6408
srud461@ecy.wa.gov

FOR IMMEDIATE RELEASE
01-28-2009

State scientists analyzing low-oxygen triggers in South Sound

OLYMPIA – Discharge water from sewage treatment plants and rivers is a major source of nitrogen in South Puget Sound during late summer and may be contributing to low dissolved oxygen levels that hurt fish. The results are early findings in a special focus on South Puget Sound by the Washington Department of Ecology (Ecology).
     
Sewage treatment plant discharge pipes – even though they discharge treated water – can contribute up to 80 to 90 percent of the combined nitrogen entering South Puget Sound from rivers and wastewater plants, according to the South Puget Sound Dissolved Oxygen Study.
     
Rivers, air deposition, sediments, septic systems, and the Pacific Ocean also send nitrogen into South Puget Sound all year long.
     
Nitrogen can be the leading cause of low dissolved oxygen. Nitrogen causes excess algae growth. As the algae die and decay, they rob the water of dissolved oxygen. In areas of Puget Sound that have low levels of dissolved oxygen, fish and other marine life become stressed and die or are forced to flee their habitat.
     
The four-year study of Puget Sound covers waters from King to Mason counties. Its goal is to determine how nitrogen from people and from natural sources affects dissolved oxygen levels in South Puget Sound.
     
State scientists’ next step is to use sophisticated computer-prediction tools to figure out how much of the problem is caused by people and how to fix the problem.
     
Addressing dissolved oxygen issues in South Puget Sound is a near-term action in the Puget Sound Partnership’s recently adopted Action Agenda.
     
“This effort is a critical first step in determining what we need to do to restore and protect oxygen levels, which are vital for life to thrive in Puget Sound,” said David Dicks, executive director of the Puget Sound Partnership.
     
Kelly Susewind, manager of Ecology’s water quality program said: “This work has been possible because of the unprecedented cooperation we’ve received from sewer districts and cities that operate treatment plants throughout South and Central Puget Sound. I think that everyone involved in the business of cleaning up our waste water knows how important it is to understand treated water’s effect on Puget Sound.”

In its assessment of water quality in 2008, Ecology identified 24 locations in South Puget Sound that are impaired due to low dissolved oxygen. Ecology identified another 27 locations as waters of concern. The lowest dissolved oxygen levels occur in Carr, Case, and Budd Inlets.
     
The South Puget Sound Dissolved Oxygen early findings say that, on an annual basis, rivers and wastewater (sewage) treatment plants south of the Tacoma Narrows sent roughly equal amounts of nitrogen into the South Sound. However, in September 2007 – a critical period for dissolved oxygen concentrations – wastewater treatment plants south of the Tacoma Narrows were the source of 80 percent of the total combined nitrogen contribution to South Puget Sound from rivers and wastewater treatment plants.  In looking at the entire study area, which reaches to just south of Edmonds, wastewater treatment plants contributed more than 90 percent of the combined river and wastewater treatment plant amounts in September.
     
People living in the Puget Sound watershed have led to a doubling of nitrogen entering South Puget Sound from the watershed. During certain times of the year, humans contribute at least 10 times the natural levels of nitrogen.
     
Ecology’s water-circulation model later this year will describe how water circulates in the South Sound. It will help scientists map the areas that human sources of nitrogen may influence. It will also quantify the amount of nitrogen coming into South Puget Sound from the Pacific Ocean. The model is a mathematical, computer-based prediction tool Ecology uses to represent a water system. Ecology uses models to visualize, predict, and determine water quality factors that may be causing low dissolved oxygen in South Puget Sound.
     
If the study shows that nitrogen reductions are necessary, Ecology may convene local jurisdictions and interest groups in either a water cleanup planning process – known as a Total Maximum Daily Load or TMDL study – or some other plan of action to achieve clean water.
     
Ecology’s Susewind said, “We would carefully evaluate costly upgrades to Puget Sound sewage treatment plants to remove nitrogen. Automatically requiring that all wastewater treatment plants remove nitrogen from their discharges may not be the best approach to improving dissolved oxygen levels. This study, when final, lays a critical foundation for decisions about the most efficient and cost-effective actions to make a difference.”
     
Read the data report and other background about the study online at:
http://www.ecy.wa.gov/puget_sound/dissolved_oxygen_study.html.

Ecology’s final report with computer prediction results is due in 2010.

###