Sediment Quality

Sediments in Puget Sound

About this indicator: King County monitors sediments in lakes, streams, and at marine sites as part of it's ambient monitoring programs. Sediment quality is an important indicator of environmental health, and along with indicators of water quality, habitat, and the aquatic food web (i.e. plankton, invertebrates, and fish), it can present a clearer picture of environmental quality. Once contaminants are washed into surface waters and attach to bottom sediments they can persist where people can be exposed to them directly or indirectly by eating fish that have been caught in our local lakes, streams, and along shores where some of these contaminants can bioaccumulate up the food chain.

Our weighting system applies 60 percent of the freshwater index and 40 percent of the marine environment index to the overall sediment quality index. The freshwater index is applied equally at 50 percent to lakes and streams. The marine environment index is applied equally at 50 percent to ambient sites and 50 percent to point source sites.

Status: Overall most of the lake stations found to have chemical concentrations high enough to probably be causing adverse effects in aquatic organisms were located in Lake Union. Contaminants were found in streams in concentrations high enough to probably be causing adverse effects in aquatic organisms. Of the ambient sampling, most stations passed all of the chemical criteria.

What you can do:

• Properly dispose of pharmaceuticals, harmful chemicals and paints, instead of pouring them down the drain or allowing them to run off the ground.
• Minimize 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 or manage met and livestock wastes.

More information about King County's Sediment Quality Index is available by continuing below for these measures:

• Large Lakes Sediment Quality
• Stream Sediment Quality
• Marine Point Source Sediment Quality
• Marine Ambient Sediment Quality

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Large Lakes Sediment Quality

About this indicator: To understand what effect chemicals in sediments may be having on aquatic life, chemical concentrations are compared to sediment quality guidelines. The Washington State Department of Ecology has not promulgated numeric freshwater sediment chemical standards, but has evaluated existing numeric sediment quality guidelines and proposed a new set of numeric guidelines, known as the floating percentile method, for use in Washington State freshwater sediments.

In addition to using the floating percentile-derived guidelines, a more widely used set of guidelines that were developed by Smith et al (1996) in the Great Lakes region in 1996 were also used. These Smith guidelines represent a good balance between sensitivity and efficiency and also include guidelines for organochlorine pesticides (DDT, dieldrin, etc.), which are not included among the floating point guidelines.

The Major Lakes Sediment Monitoring Program was begun in 1999 in Lakes Sammamish, Washington, and Union. An updated 10-year program was launched in 2007 to collect sediment quality information near storm drains, swimming beaches, and wildlife habitat areas. Additionally, a two-tiered sampling design allows for the assessment of long term trends in the deep main basins of the three major lakes.

This indicator is divided into three ratings: 1) adverse effects to aquatic organisms from chemical concentrations are unlikely; 2) adverse effects to aquatic organisms from chemical concentrations are uncertain; and 3) adverse effects to aquatic organisms from chemical concentration are probable. The three large lakes, Lake Washington, Union and Sammamish are weighted equally at 30 percent each for this indicator.

Status: A total of 60 stations have been sampled in Lakes Sammamish, Washington, and Union. Overall, most of the stations found to have chemical concentrations high enough to probably be causing adverse effects in aquatic organisms were located in Lake Union. Lake Sammamish sediment quality was the best of the three lakes, while Lake Washington sediment quality was mostly good except for a few localized areas.

Influencing factors: Point sources, stormwater, and other discharges such as irrigation runoff, can wash contaminants into surface waters. Additionally, historical contamination from the industrial and commercial areas surrounding Lake Union is still evident.

Existing DNRP response: King County is committed to monitoring large lake sediment quality to ensure their continued health, as well as the health of the public who live near or use the lake's many resources.

Priority new actions: The updated 10-year Major Lakes Sediment Monitoring Program will continue to collect sediment quality information near storm drains, swimming beaches, and wildlife habitat areas. King County will continue to conduct hazardous waste management and outreach to reduce contaminant discharges, and coordinate trouble calls to investigate illegal and accidental spills reported by citizens.

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Streams Sediment Quality

About this indicator: To understand what effect chemicals in sediments may be having on aquatic life, chemical concentrations are compared to sediment quality guidelines. The Washington State Department of Ecology has not promulgated numeric freshwater sediment chemical standards, but has evaluated existing numeric sediment quality guidelines and proposed a new set of numeric guidelines, known as the floating percentile method, for use in Washington State freshwater sediments.

In addition to using the floating percentile-derived guidelines, a more widely used set of guidelines that were developed by Smith et al. in the Great Lakes region in 1996 were also used. These Smith guidelines represent a good balance between sensitivity and efficiency and also include guidelines for organochlorine pesticides (DDT, dieldrin, etc.), which are not included among the floating point guidelines.

The Stream Sediment Monitoring Program was begun in 1987 in WRIAs 8 and 9 as part of the overall Lakes and Streams Ambient Monitoring Program. An updated 10-year program began in 2004 to monitor the effects of all sources (point sources, stormwater, and other discharges) to the streams. Additional parameters were added to the existing sediment monitoring program to better understand the range of contaminants that affect sediment quality. A two-tiered sampling design allows for the assessment of sediment quality in individual stream basins as well as long-term trend analysis.

This indicator is divided into three ratings: 1) adverse effects to aquatic organisms from chemical concentrations are unlikely; 2) adverse effects to aquatic organisms from chemical concentrations are uncertain; and 3) adverse effects to aquatic organisms from chemical concentration are probable.

Status: A total of 70 stations have been sampled in King County streams between the September 2004 and August 2006. Metals, phthalates, and legacy pesticides, such as DDT have been found in a few locations in concentrations high enough to probably be causing adverse effects in aquatic organisms. Most of Bear and Little Bear Creek sediment quality was rated as having unlikely adverse effects.

Influencing factors: Point sources, stormwater, and other discharges such as irrigation runoff, can wash contaminants into surface waters.

Existing DNRP response: King County is committed to monitoring stream sediment quality to ensure their continued health, as well as the health of the public who live near or use the streams' many resources.

Priority new actions: The updated 10-year Streams Sediment Monitoring Program will continue to collect sediment quality information to monitor the effects of all sources (point sources, stormwater, and other discharges) to the streams. King County will continue to conduct hazardous waste management and outreach to reduce contaminant discharges, and coordinate trouble calls to investigate illegal and accidental spills reported by citizens.

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Marine Point Source Sediment Quality

About this indicator: Washington State's Sediment Management Standards seeks to reduce and ultimately eliminate adverse effects on biological resources and any significant human health risk from surface sediments in marine, low salinity or estuarine and freshwater environments. The Sediment Quality Standard, or "no adverse effects level," is the most protective chemical standard for marine sediments. The Cleanup Screening Level, or the "minor adverse effects level," helps identify areas of potential concern that may be designated cleanup sites.

The Sediment Quality Standard has been selected as the indicator because it is the more sensitive of the two criteria for environmental protection. Data from 2001 are used because they represent the most recent comprehensive survey of sediment quality in King County. In 2001, sediment sites were divided into two categories. Ambient sites were chosen to reflect general, or ambient, environmental conditions. Point source stations are located near King County wastewater treatment plant outfalls and combined sewer overflow outfalls. Data from 2001 is still relevant for analysis because sediments (particularly those that are polluted) move slowly and do not change much over five years unless clean up efforts have been taken.

Details related to a 2007 sampling event for ambient stations are presented with the indicator for Marine Environment — Ambient Sediment Quality.

Status: Of the 15 point source-related sites that exceed the Sediment Quality Standard, eight do not require clean up or monitoring. Six of the remaining seven point source sites are associated with combined sewer overflow outfalls, and one is associated with an emergency overflow.

Influencing factors: Many pollutants found in the environment are not detected in water, but are attached to sediment particles. Once in the sediments, these pollutants can directly harm marine organisms or be reintroduced to the food chain through the organisms found in marine sediments.

Existing DNRP response: Strategies to achieve the outcome goal focus on collaborating with other organizations, including the City of Seattle, Port of Seattle, and Boeing, with which King County has joined to form a public-private partnership called the Lower Duwamish Waterway Group. This group will be funding cleanups at "early action sites" as part of the Lower Duwamish Waterway federal Superfund process. A partial cleanup was completed in 2004 at the first of these sites, the Duwamish/Diagonal Way site. A follow-up cleanup was completed in 2005.

Priority new actions: The cleanup of the Lower Duwamish Waterway includes a multi-agency, source-control effort to reduce the potential for future recontamination. Additional sediment site cleanups may be completed later under Superfund, or as part of other activities in the Duwamish waterways. It is expected that three to five additional sites could be addressed by 2010.

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Marine Ambient Sediment Quality

About this indicator: Washington state's Sediment Management Standards seeks to reduce and ultimately eliminate adverse effects on biological resources and any significant human health risk from surface sediments in marine, low salinity or estuarine and freshwater environments. King County developed a new ambient marine sediment sampling program in 2007. Data from subtidal marine sediment samples collected from stations throughout the Puget Sound area within King County were compared to the State of Washington Sediment Management Standards (SMS) chemical criteria (Chapter 173-204 WAC).

As part of the new plan, King County will be collecting subtidal marine sediment samples from eight locations in Elliott Bay, every two years, and from three locations in the Puget Sound main basin and three associated embayments (Salmon Bay, Fauntleroy Cove, and Quartermaster Harbor), every five years. In this year, sediment chemistry data from 14 locations were used for this indicator.

Status: Eleven of 14 stations (79%) passed all SMS chemical criteria. Three of 14 stations (21%) failed one or more SMS chemical criteria. The station in Quartermaster Harbor failed the mercury criterion, the station in East Passage failed the bis(2-ethylhexyl) phthalate criterion, and the station at Harbor Island failed the criteria for mercury and butyl benzyl phthalate.

Influencing factors: Many pollutants found in the environment are not detected in water, but are attached to sediment particles. Once in the sediments, these pollutants can directly harm marine organisms or be reintroduced to the food chain through the organisms found in marine sediments.

Existing DNRP response: King County will continue to monitor ambient sediment quality in its marine waters every two years in Elliott Bay and every five years in the central basin of Puget Sound and associated embayments.

Priority new actions: There are no "priority new actions" planned for the next year.

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