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Puget Sound Marine Monitoring

The best decisions are based on Sound information

For questions about the King County Puget Sound Marine Monitoring Program, please contact

Routine Beach Monitoring Program

Map icon for active stationactive station  Map icon for inactive stationinactive station

The marine nearshore and intertidal environments can be particularly susceptible to pollution, given their proximity to both point and non-point sources, such as stormwater pipes, wastewater treatment plants, and freshwater creeks and streams. Many of King County’s marine beaches are within parks and provide a source of primary-contact recreation through wading, swimming, kayaking, fishing, and SCUBA diving. Nearshore and intertidal areas are also important marine ecosystem components, providing spawning areas for several species of forage fish and important habitat for juvenile salmonids. Water-borne pathogens can potentially cause disease in humans resulting from direct contact with the water during recreational activities. Excess nutrients can potentially cause eutrophication in nearshore areas or cause preferential growth of unwanted marine flora such as sea lettuce (Ulva spp.), which can significantly alter the habitat required by some forage fish and their predators.

King County monitors water quality monthly at 20 beach/nearshore stations and one associated stream station, located in Puget Sound, Elliott Bay, and Quartermaster Harbor. Seventeen of the beach/nearshore monitoring stations are located along the western shoreline of King County, and three are located on Vashon and Maury Islands. Ten beach stations are located onshore or in the vicinity of King County wastewater treatment or conveyance facility outfalls. These include the West Point wastewater treatment plant (2 stations), the Brightwater treatment system, the Vashon wastewater treatment plant, the Alki and Carkeek CSO treatment plants, and the South Magnolia, Denny Way, SW 63rd Street, and Barton Street CSOs. All 20 of the beach stations are monitored for bacteria, temperature, nutrients, and salinity using standard methodology . The one stream station located in Piper’s Creek is monitored for bacteria, temperature, and nutrients. The Piper’s Creek stream monitoring station provides background information for the beach station at Carkeek Park, which is located at the mouth of the creek as it enters Puget Sound.

Scientist taking beach water samples Beach water samples are collected at approximately knee depth by inverting sample containers just above the water surface, then sinking the bottle down to approximately 12-inches below the water surface. The bottles are not filled completely in order to allow room for mixing.

Marine beach water quality, and other discrete water data, can be found here. Please contact with any questions about the program.

Information for Marine Swimming Beaches