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Puget Sound Marine Monitoring

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

Routine Subtidal Sediment Monitoring Program

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

scientist colleccting sediment samplesThe primary goal of King County’s marine ambient sediment monitoring program is to collect data of known quality in order to effectively characterize marine sediments within the County’s borders. King County has collected sediment quality data from subtidal, ambient monitoring stations for many years. These subtidal monitoring stations have been located within Elliott Bay and in the Central Basin of Puget Sound, proximal to the City of Seattle. Sampling locations have traditionally been located to monitor sediment quality in areas within the general vicinity but away from the direct impact of potential point-source pollution such as wastewater and storm water outfalls and general non-point sources such as the Duwamish River. King County’s previous ambient subtidal sediment monitoring program evaluated sediment quality at four stations in Elliott Bay, two stations in the Puget Sound Central Basin, and one station in Shilshole Bay. Samples were collected from these stations biennially between 1996 and 2004 and annually at several of the stations, as well as others, prior to 1996.

The former subtidal sediment monitoring program was temporarily discontinued after 2004 to allow King County staff scientists to evaluate data generated from the program as well as other data collection efforts within the region. Following this review period, King County expanded its marine ambient subtidal sediment monitoring program to focus on sediment quality in Elliott Bay, while still monitoring truly ambient sediment quality in the Central Basin of Puget Sound as well as three smaller embayments of interest.

The Elliott Bay sediment monitoring program includes eight stations with sampling occurring every two years. The other six stations are sampled every five years. The 14 stations were sampled initially in 2007.

The six stations located in the Central Basin and associated smaller embayments are sampled every five years. The frequency of sampling for these six stations should be sufficient to monitor long-term trends in sediment quality. The three stations in the Central Basin, which represent ambient sediment conditions in the deep, depositional areas of Puget Sound, include:

  • Station KSBP01 – located off of Point Jefferson. This station will represent conditions in the northern portion of the Central Basin and is one of King County’s long-term water column monitoring stations.
  • Station LSML01 – located off of West Seattle. This station will represent conditions in the center portion of the Central Basin and is one of King County’s long-term sediment monitoring stations.
  • Station NSEX01 – located in East Passage. This station will represent conditions in the southern portion of the Central Basin and is another of King County’s long-term water column monitoring stations.

The three stations located in the small embayments, which represent specific areas of interest due to potential anthropogenic impacts, include:

  • Station KSRU03 – located in outer Salmon Bay, just downstream from the Hiram Chittenden locks. This area receives a high level of small and large vessel traffic entering and exiting the locks.
  • Station LSVV01 – located in Fauntleroy Cove. This area has a history of water quality issues, receives a large amount of freshwater input, and is impacted by ferry traffic at the Fauntleroy ferry dock.
  • Station MSVK01 – located in inner Quartermaster Harbor. This area is of importance as habitat for both shellfish and Pacific herring. This shallow, quiescent embayment receives a moderate amount of seasonal small vessel traffic.

sedimentThe eight stations located in Elliott Bay are sampled every two years. This more-frequent sampling will allow King County and other decision-makers to better evaluate temporal changes in sediment quality and help assess the potential positive impacts to the marine environment from various sediment cleanup projects and other riparian improvements in Elliott Bay. Four of the Elliott Bay stations have long-term sediment quality data sets that will continue with King County’s new sediment sampling program. These stations are:

  • LSCW02 – located at the hypothetical boundary-line between Elliott Bay and the Central Basin of Puget Sound;
  • LTCA02 – located in the center of Elliott Bay;
  • LTED04 – located in the center of Elliott Bay, inshore of LTCA02; and
  • LTDF01 – located along the central Seattle waterfront, near Pier 66.

These four stations form a rough east-west transect away from locations of potential point-source impacts to the sediment. Four new Elliott Bay stations were added to the monitoring program in 2007 to assess specific areas of the bay. These stations are:

  • KSZY01 – located just offshore of Piers 90/91. This area has historically received high heavy-vessel traffic and will continue to receive large ships when cruise liners begin using these docking facilities.
  • LTAA02 – located just offshore of the grain terminal. This area has also historically received high heavy-vessel traffic and docking.
  • LTGF01 – located just offshore of the northern end of Harbor Island. This location is in an area of heavy industry, including fuel storage and transfer, shipbuilding and repair, and the transportation industry.
  • LSHZ08 – located just offshore of Cove 2 at Seacrest Park. This area has high usage by recreational SCUBA divers, including diving classes, which includes a high incidence of primary contact with bottom sediments, especially by student divers.

View a copy of the most recent King County routine ambient sediment monitoring program sampling and analysis plan .

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