Presentation Abstract
To help protect regional water quality, in 2012 King County initiated a study to review the impacts of combined sewer overflows (CSOs) and other sources of pollution to inform the region of the benefits of CSO control. King County’s Water Quality Assessment and Monitoring Study (Study) explored water quality in Lake Union/Ship Canal, Elliott Bay, and the Duwamish Estuary, where the County is planning projects to reduce the frequency of CSOs to an average of one untreated overflow per site per year over a 20-year moving average. Reducing CSO frequency to this degree is known as CSO “control” and is required by the terms of King County’s CSO consent decree and by Washington State requirements. Uncontrolled CSOs contribute about 85 percent of the annual fecal bacteria load to the waterbodies. Control of CSOs by 2030 is projected to reduce the total load by about 80 percent. The largest annual loads of copper are from leaching from antifouling vessel paint and stormwater discharges. Washington State laws to reduce copper in these products is projected to reduce copper loading by about 50 percent by 2030. The largest annual loads of polycyclic aromatic hydrocarbons (PAHs) are from leaching from creosote-treated pilings. Piling removal is projected to reduce PAH loads by 30 percent by 2030. Direct stormwater discharges and upstream sources are the predominant loading pathways for other contaminants studied. Annual load reductions of less than 10 percent were projected by 2030 for the other contaminants. The Study demonstrates that CSO control will substantial improve bacteria levels in the waterbodies, but that additional water quality improvement projects are needed to meet surface water quality standards for other contaminants.
Session Title
Monitoring Stormwater Impacts on Contaminants in Receiving Waters
Keywords
CSOs, Duwamish, Elliott Bay, Lake Union, pathways, water quality
Conference Track
SSE3: Fate, Transport, and Toxicity of Chemicals
Conference Name
Salish Sea Ecosystem Conference (2018 : Seattle, Wash.)
Document Type
Event
SSEC Identifier
SSE3-642
Start Date
6-4-2018 1:30 PM
End Date
6-4-2018 1:45 PM
Type of Presentation
Oral
Genre/Form
conference proceedings; presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Combined sewer overflows--Washington (State)--Lake Union; Combined sewer overflows--Washington (State)--Elliott Bay; Combined sewer overflows--Washington (State)--Duwamish River Estuary; Runoff--Washington (State)--King County; Water quality management--Washington (State)--King County
Geographic Coverage
Lake Union (Wash.); Elliott Bay (Wash.); Duwanish River Estuary (Wash.)
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Included in
Fresh Water Studies Commons, Marine Biology Commons, Natural Resources and Conservation Commons, Terrestrial and Aquatic Ecology Commons
Past, present, and future water quality in Lake Union/Ship Canal, Elliott Bay, and the Duwamish Estuary and the benefits of combined sewer overflow control and other projects
To help protect regional water quality, in 2012 King County initiated a study to review the impacts of combined sewer overflows (CSOs) and other sources of pollution to inform the region of the benefits of CSO control. King County’s Water Quality Assessment and Monitoring Study (Study) explored water quality in Lake Union/Ship Canal, Elliott Bay, and the Duwamish Estuary, where the County is planning projects to reduce the frequency of CSOs to an average of one untreated overflow per site per year over a 20-year moving average. Reducing CSO frequency to this degree is known as CSO “control” and is required by the terms of King County’s CSO consent decree and by Washington State requirements. Uncontrolled CSOs contribute about 85 percent of the annual fecal bacteria load to the waterbodies. Control of CSOs by 2030 is projected to reduce the total load by about 80 percent. The largest annual loads of copper are from leaching from antifouling vessel paint and stormwater discharges. Washington State laws to reduce copper in these products is projected to reduce copper loading by about 50 percent by 2030. The largest annual loads of polycyclic aromatic hydrocarbons (PAHs) are from leaching from creosote-treated pilings. Piling removal is projected to reduce PAH loads by 30 percent by 2030. Direct stormwater discharges and upstream sources are the predominant loading pathways for other contaminants studied. Annual load reductions of less than 10 percent were projected by 2030 for the other contaminants. The Study demonstrates that CSO control will substantial improve bacteria levels in the waterbodies, but that additional water quality improvement projects are needed to meet surface water quality standards for other contaminants.
