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Department of Natural Resources and Parks (DNRP)


2011 Rating Red

Marine Water Quality

Marine Environment

Pie chart showing Marine Water Quality components
Indicator Key

About this indicator: King County's Marine Water Quality includes information about the conditions of marine waters.

Status: While, in general, the quality of open waters in Puget Sound is fair, marine water quality conditions in certain areas of King County show evidence of degradation. Waters that are in protected areas without much current are of concern.

Influencing factors: Stormwater carrying nutrients from septic systems, chemicals from motor vehicles and nitrogen from fertilizers degrade marine water quality and reduce oxygen levels for the animals that live and depend on Puget Sound habitats.

What you can do:

  • Properly dispose of harmful chemicals, including unused pharmaceuticals and latex paints.
  • Maintain, repair, or replace failing private septic systems.
  • Minimize the use of fertilizers and pesticides by practicing natural yard care.
  • Wash your car on the grass or gravel instead of on the street or driveway, or take it to a car wash.
  • Properly dispose of pet waste

More information about King County's marine waters is available by continuing below for these measures:

Marine Water Quality Index

  Graph showing Percent marine offshore monitoring sites at moderate or high water quality concern levels Map showing Marine Eutrophication
Marine water quality index
2011 Findings

About this indicator: King County conducts monthly water quality monitoring at 14 offshore locations in Puget Sound, which includes 7 stations located at wastewater treatment plant and CSO outfall pipes. Offshore marine waters in King County are monitored for temperature, salinity, density, dissolved oxygen, light transmittance, nutrients, and chlorophyll. These variables can be used to assess eutrophication, (the process by which dissolved oxygen concentrations are depressed due to algae growth primarily caused by nutrients), sewage waste (ammonia), food availability to secondary producers (chlorophyll), and marine water habitat quality (dissolved oxygen, temperature, salinity).

Status: 2011 findings indicate that the water quality at 12 stations is at a low level of concern. These same 12 stations were also at a low level of concern in 2010. The two stations in Quartermaster Harbor were at a high level of concern in both 2009 and 2010. For 2011, the station in the inner harbor received a moderate level of concern ranking due to low dissolved oxygen values and three consecutive months of low dissolved inorganic nitrogen (DIN). The station in the middle harbor in 2011 again received a high level of concern ranking due to low dissolved oxygen values and six consecutive months of low DIN. These two Quartermaster Harbor sites are currently monitored with in situ water quality monitoring equipment due to the high level of concern for these waters.

The percentage of stations of Moderate or High Concern is 14.3%, which is the same as 2010 and a decrease from 2009 (28.6%).

Influencing factors: Vertical water density patterns can be indicators of an area's potential sensitivity to developing low dissolved oxygen conditions. Low oxygen conditions are harmful to fish and other aquatic life and may occur as a result of the natural flow of low oxygenated Pacific Ocean water into the deep main basin of Puget Sound, in addition to processes such as eutrophication. Persistently low nitrate concentrations in surface water can indicate a potential sensitivity to nutrient-rich input such as stormwater runoff, industrial waste discharges, septic systems, and flow from rivers. Ammonia can be found at elevated concentrations as a byproduct of sewage, agricultural practices, and fertilizer use in urban areas.

Existing DNRP response: DNRP will continue to operate its wastewater treatment plants and conveyance system effectively to maintain low levels of nutrients discharged into marine waters. The new Brightwater Treatment System will use state of the art technology to reduce nutrients and other pollutants. King County, along with other monitoring partners, is currently involved in a four-year study to assess the role of nitrogen, if any, on dissolved oxygen levels in Quartermaster Harbor. Nutrient levels are also addressed by the agency through stormwater control management practices. Additionally, DNRP will continue to play an active role in the Puget Sound Partnership toward improving water quality throughout the entire Puget Sound.

Priority new actions: Stratification intensity and its persistence is beyond King County's influence, but should be monitored as it is an important indicator of areas sensitive to possible water quality problems.

Technical notes for Marine Water Quality Index

For definitions and more detail.

Fecal Bacteria in Offshore Marine Waters (ambient and outfall)

About this indicator: The presence of fecal bacteria in water bodies indicates contamination with the fecal material of humans, birds, or other warm-blooded animals. Although these bacteria are usually not harmful themselves, they often occur in conjunction with other disease-causing pathogens, and their presence at high levels indicates an increased possibility that people might get sick if they come into contact with the water.

Washington State has a marine surface water quality bacteria standard based upon fecal coliforms. This standard was derived for the protection of human health and addresses water quality requirements for both primary contact recreational uses (e.g. swimming and SCUBA diving) as well as the consumption of shellfish. This fecal coliform standard is a geometric mean of 14 colony forming units /100ml, calculated over a 12-month sampling period.

King County conducted monthly water quality monitoring in 2011 at 14 offshore locations in Puget Sound. Offshore monitoring locations are divided into two categories, ambient and outfall stations. Ambient stations are chosen to reflect general, or ambient, environmental conditions, while outfall stations are located at King County wastewater treatment plant outfalls and county-operated combined sewer overflow outfalls. Monitoring occurred at seven outfall stations and seven ambient stations in 2011. Ambient stations were located in the Central Basin of Puget Sound as well as Elliott Bay and Quartermaster Harbor.

The status of this indicator is based upon the geometric mean of the fecal coliform bacteria counts over the 12-month period of calendar year 2011 in samples collected from 14 monitoring stations at a depth of one meter below the surface.

Status: All ambient and outfall stations met the fecal coliform bacteria geometric mean standard in 2011. Fecal coliform bacteria counts do not appear to be an ongoing concern in offshore surface marine waters within King County.

Influencing factors: Fecal coliform bacteria can enter Puget Sound from domestic animals, wildlife, storm water runoff, wastewater discharges, and failing septic systems. Non-point source pollution (e.g. storm water runoff and agriculture) is the major cause of marine water bacterial contamination.

Existing DNRP response: DNRP will continue to manage its wastewater treatment plants and conveyance system effectively. The county is working with the Puget Sound Partnership effort toward protecting and restoring the health of marine waters.

Priority new actions: No major changes to the offshore marine water quality monitoring program are planned for 2012.

Map showing fecal bacteria at ambient monitoring sites
Fecal bacteria at ambient monitoring sites
2011 Findings
Click to download the PDF version.
Map showing fecal bacteria at wastewater outfall sites
Fecal bacteria at wastewater outfall sites
2011 Findings
Click to download the PDF version.

Technical notes for Fecal Bacteria in offshore Marine Waters

For definitions and more detail.

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We welcome your feedback and suggestions to improve this site, such as:

  • Other reliable environmental data sources for King County
  • Adjustments to the weightings for indicators and performance measures
  • Mistakes to fix

Share your thoughts by sending an e-mail to Richard Gelb, DNRP Performance Measurement Lead, at so your input can be considered for subsequent updates.