Sample Design and Methods - Regional and Urban Bays

Environmental Management Application

The Marine Sediment Monitoring Program regional and urban bay elements provide environmental managers with annual characterization (status) of sediment condition at different locations and at nested geographic scales throughout Puget Sound. Changes in sediment condition over time (trends) are assessed by comparison of recently collected and baseline data to determine whether sediment quality in each Puget Sound study area is improving, degrading, or remaining the same over time.

Sampling Design

From 1997 to 1999, Ecology conducted sediment monitoring in partnership with the National Oceanic and Atmospheric Administration (NOAA) National Status and Trends (NS&T) Bioeffects Assessment Program. Three hundred sediment samples throughout northern, central, and southern Puget Sound study areas were collected for this program using a stratified random sampling design. These data were used to calculate the spatial extent of sediment quality degradation throughout the Sound.

This sampling design was later modified with assistance from EPA’s Aquatic Resources Monitoring Design and Analysis Team. A spatially-balanced generalized random tessellation stratified (GRTS) multi-density survey design was applied to better balance the distribution of stations through the study area. The original study area was expanded to include the bays and inlets of the San Juan Archipelago, Admiralty Inlet, and eastern Strait of Juan de Fuca (sampled in 2002-2003), and a nested set of sampling frames was developed at different geographic scales, including:

Regions and urban bays are sampled on 10-year and 6-year rotational sampling schedules, respectively. Puget Sound-wide and stratum data are summarized once every 10 years. This nested design allows Marine Sediment Monitoring Team scientists to characterize sediment quality at multiple geographic scales and over different periods of time.

The six urban bays chosen for the embayment-scale sediment monitoring surveys are “nested” within the larger-scale regions. Each year forty newly selected stations are sampled in one region, and 30 stations (both those used for previous sampling and some newly selected stations) are sampled in one bay.

The Sediment Quality Triad includes sediment chemicals, laboratory tests of sediment toxicity, and characterization of sediment-dwelling invertebrates known as benthos, are measured from sediments collected from each station (parameters).


Quality Assurance Project Plan

Dutch, M., V. Partridge, S. Weakland, K. Welch, and E. Long. 2009. Quality Assurance Project Plan: The Puget Sound Assessment and Monitoring Program Sediment Monitoring Component. Washington State Department of Ecology Publication 09-03-121. 98 pp.

Additional Information

Through the Urban Waters Initiative, Ecology’s Toxic Cleanup, Hazardous Waste, and Water Quality Programs have aligned their source control and cleanup activities to reduce toxic chemical pollution from stormwater runoff and other sources discharging to two urban bays:

  • Elliott Bay and the adjoining waterways of the lower Duwamish River
  • Commencement Bay

These actions are meant to reduce toxics entering the bays of Puget Sound and prevent re-contamination of sediments at sites that have been cleaned up or are in the process of being cleaned up.

Ecology is involved in other work conducted in these urban bays as part of Puget Sound Initiative clean up of priority bays and other major cleanup locations. These bays include: