Routine Beach Monitoring Program

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 28 beach/nearshore stations and one associated stream station, located in Puget Sound, Elliott Bay, Quartermaster Harbor, and the Duwamish River. Twenty-two of the beach/nearshore monitoring stations are located along the western shoreline of King County, one station is located in the Duwamish River, and five are located on Vashon and Maury Islands. Nine beach monitoring 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 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 28 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.

Beach water samples are collected at approximately hip 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. Samples are collected in this manner from 25 of the 28 beach stations. Three stations, located in Elliott Bay (LTEH02 and LSGY01) and Shilshole Bay (KSQU01) are collected by lowering a bucket from a pier and then transferring the water samples into the containers.

Data for the routine beach monitoring program are not currently available for download through the web site. Please contact Scott Mickelson with any data requests.