Is Metal Detecting allowed: YES
You can view the state regulations HERE
Metal detecting is permitted at more than 30 state parks throughout Washington. Metal Detecting areas vary in each park. Users of metal detectors must register first with Washington State Parks and comply with posted regulations. The registration form, rules, and a list of parks that allow detecting may be found online in the Metal Detecting in Washington State Parks brochure (PDF), or by calling park staff at 360-902-8500 or from the Washington Telecommunications Relay Service at 800-833-6388. You also may complete the registration form online.
FMDAC Disclaimer: FMDAC assumes no responsibility for any person who knowingly or accidentally violates any state park regulation. Although FMDAC will try to keep this information current we cannot anticipate how each regulation will be interpreted by a specific park department, park employee or other government employee. It is the sole responsibility of each individual to know and obey the regulations of the park or area they are visiting and or metal detecting.