Ecology is reviewing Navy cleanup plans for this and nearby closed-off areas affected by work on aircraft instruments when the park was a Naval air station.
The Office of Radiation Protection regulates and monitors radioactive materials in Washington.
The Washington departments of Ecology and Health are overseeing efforts by the U.S. Navy to assess and safely clean up low-level radioactive remnants from former work on aircraft instruments. This work took place in the mid- 20th century when what's now Magnuson Park was a Naval air station.
In addition to this direct link, you can go to this page on the DOH website. Additional information is available from Ecology and the Navy.