Water column samples are collected monthly from 18 stations. Nine outfall monitoring stations are located at outfalls for the West Point, South, and Vashon treatment plants, the Alki and Carkeek combined sewer overflow (CSO) treatment plants, the Elliott West and Henderson/MLK/Norfolk CSO treatment facilities, and the Hanford/Lander and Barton CSOs. Seven ambient monitoring stations are located throughout the Central Basin. Water samples are collected from between one and seven depths at each offshore station, depending on the total station depth. View a table of parameters analyzed at each depth Two additional ambient stations, collected as part of the marine offshore program, are located in the Duwamish River, just upstream of Harbor Island and at the 16th Avenue South bridge, with samples collected from two depths at each station.

Laboratory analytes include fecal coliform and enterococcus bacteria, chlorophyll-a and pheophytin pigments, solids, and nutrients (ammonia, nitrite/nitrate nitrogen, total Kjeldahl nitrogen, total phosphorus, and silica). Bacteria samples are collected from all sampling depths at each of the outfall monitoring stations but only from the surface at ambient monitoring stations, with the exception of the Quartermaster Harbor and Duwamish River samples. Bacteria samples will be collected from both depths at each Quartermaster Harbor and Duwamish River ambient station.

Currently, only in situ CTD water column profile data are available for download through the web site. These data are available by visiting the Offshore CTD Monitoring page and selecting a station from the map. Data from discrete sampling depths (nutrients, bacteria, phytopigments, solids) can be found here. Please contact MarineWQ@kingcounty.gov with any questions about the program.