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Learn About Quartermaster Harbor Water Quality

A four-year study to evaluate the role of nitrogen in observed late summer, low-level dissolved oxygen events in Quartermaster Harbor has passed the half-way point, and study participants want to share their updated findings with the public at an Oct. 12 workshop.

King County, in partnership with the Environmental Protection Agency, the University of Washington-Tacoma, Washington State Department of Ecology (DOE) and the Vashon-Maury Island Groundwater Protection Committee, will provide the progress report in a workshop beginning with an open house at 6:30 p.m. followed by a presentation starting at 7 p.m. in the Vashon High School Commons.

Low dissolved oxygen levels can harm marine life, including fish, shellfish and other marine organisms. The nitrogen loading study is designed to determine the causes of the low dissolved oxygen problem and identify potential solutions.

The Oct. 12 workshop will provide participants with information on potential nitrogen management strategies being considered, offer an opportunity to ask questions and make comments about the study.

Curtis DeGasperi, King County’s study manager, said work has been proceeding to refine initial nutrient loading estimates.

"A sediment nutrient release study has been completed to check the initial loading estimate that indicated harbor sediments were potentially a significant source of nutrients during the low dissolved oxygen period," DeGasperi said.

Studies have also been completed to trace the source of elevated nitrogen observed in Mileta Creek and sample the large number of unmonitored streams along the shoreline of Quartermaster Harbor.

Also, a model of the harbor’s water circulation and water quality is under development, and will help study participants evaluate the role of nitrogen inputs in the low dissolved oxygen events.

"The completed study will provide us with a better understanding of the nitrogen loading in Quartermaster Harbor, the impact of nitrogen on low dissolved oxygen events and help guide nitrogen loading management efforts on Vashon-Maury Island," DeGasperi said.

The Quartermaster Harbor Nitrogen Management Study, which began in 2009 and runs through 2012, is being conducted in three phases:

Phase one will estimate the nitrogen loadings from various potential sources, using existing data and published literature values, and by preliminary water quality sampling of streams, groundwater and marine waters;

Phase two will build upon the results of the phase-one work by collecting additional data, modeling the contributing nitrogen loadings into Quartermaster Harbor and developing a hydrodynamic model of the harbor to simulate water circulation and quality conditions.

Phase three will link the nitrogen loadings to Quartermaster Harbor dissolved oxygen levels by simulating the effects of different nitrogen management scenarios there.

Extensive surface, ground and marine water data are also being collected as part of this project. Documents and reports for the project are available at

The cost of the study is estimated at $893,000. Of that amount, $625,000 is being provided by a grant from the federal Environmental Protection Agency, with the remaining funding coming from King County, the University of Washington-Tacoma and DOE.

New policy recommendations for nitrogen management on Vashon-Maury Island are being developed working with stakeholders for consideration in the next update of the King County Comprehensive Plan, which is scheduled for 2012.

For more information about the Quartermaster Harbor nitrogen loading study or to request a presentation concerning the study, contact Larry Stockton at 206-296-1910 or