Untreated stormwater has been identified as a major contributor of contaminants and habitat degradation in urban water bodies. As new stormwater controls and treatment facilities are implemented, it is necessary to assess their effectiveness in the field and their potential to improve water quality in receiving water bodies. This study evaluates the effectiveness of stormwater treatment facilities recently added along the Aurora Corridor (part of State Route 99) in Shoreline, Washington, where highway, commercial and residential stormwater is received by Echo Lake. The goals of the Aurora Corridor Project include improving traffic safety, traffic flow, streetscape amenities, and stormwater quality along the three-mile stretch of the Aurora highway within the City of Shoreline. Construction within the Echo Lake drainage basin began in 2011 and is scheduled to be completed at the end of 2015.

This study was designed to address data gaps identified by the Washington State Stormwater Work Group (SWG) in the effectiveness of stormwater treatment technologies used in the Puget Sound Region. The SWG represents local, state and federal government agencies, economic stake holders, and researchers, and was formed under the leadership of the Puget Sound Partnership (PSP) and Washington State Department of Ecology in 2008 to develop a Stormwater Monitoring and Assessment Strategy for the Puget Sound Region. Stormwater Action Monitoring (SAM), formerly Regional Stormwater Monitoring Program (RSMP), was created out of this process and coordinates the funding for this and several other effectiveness studies.

This site was selected because Echo Lake is part of an ongoing long-term monitoring program and the stormwater treatment design allows sampling of stormwater both before and after stormwater treatment. Echo Lake is a small surface water-fed lake that drains to the larger Lake Ballinger, and is part of the McAleer Creek basin and Lake Washington watershed.

Project objectives

This study will evaluate the effectiveness of stormwater treatment facilities newly added along the Aurora Corridor in Shoreline, where highway runoff is received by Echo Lake. The project goals are to evaluate individual treatment features, as well as the system as a whole, for their ability to improve the quality of stormwater runoff and reduce peak flows. The objectives are as follows:

Individual treatment features

• Objective 1 – Evaluate the effectiveness of individual stormwater treatment installations at reducing solids, nutrients, bacteria, metals, select organic contaminants and toxicity in highway runoff in Shoreline.

System-wide

• Objective 2 – Evaluate the flow control benefits of the system-wide stormwater detention tank system, and any additional reduction of solids, nutrients, bacteria, metals and select organic contaminants that occur.
• Objective 3 – Assess changes in stormwater quality in this system by comparing historical stormwater data to current stormwater quality before and after treatment.
• Objective 4 – Identify if nutrient and bacteria levels have changed in Echo Lake over time, and how these changes correspond to changes in stormwater infrastructure in the contributing basin. The purpose of this analysis is to consider potential effects to the receiving water body as a piece of the discussion, not to establish a causal relationship.

Team members

King County team members include scientists from the Science and Technical Services Section and King County Environmental Laboratory. The team also includes personnel from City of Shoreline – Public Works, as well as, an SAM coordinator from Washington State Department of Ecology, and SAM technical liaison from Washington State Department of Transportation. Pacific Rim Laboratories has been contracted to analyze samples for PCB congeners, and Laboratory Data Consultants will provide data validation services.

Partners

Washington State Department of Ecology 

Stormwater Action Monitoring

Stormwater Work Group  (SWG)

SWG Subgroup: Selection of Effectiveness Studies 

Project schedule

Sampling Project Plan: June 2015
Field Investigation: Fall 2015 through 2016
Final Report: End of 2017

Project documents

Stormwater Retrofit Monitoring in the Echo Lake Drainage Basin Project documents are available in Adobe Acrobat format. For help using Acrobat files, please visit our Acrobat help page.

• Echo Lake Historical Data Technical Memorandum
• Quality Assurance Project Plan (QAPP)

Final report

• Monitoring Stormwater Retrofits in the Echo Lake Drainage Basin – SAM Effectiveness Study
• Appendices (all)
  • Appendix A: Additional Site Information
  • Appendix B: Chain of Custody Sheets
  • Appendix C: Field Sampling Methods
  • Appendix D: Analytical Methods
  • Appendix E: Data Analysis Methods
  • Appendix F: Part 1, Raw Validated Data and PCB Congener Sums
  • Appendix F: Part 2, Validated KCEL Data
  • Appendix F: Part 3, Validated PCB Data
  • Appendix G: Data Quality Assessment
  • Appendix H: Detailed Results
  • Appendix I: Summary of Flow Monitoring
  • Appendix J: Annotated Summary of Maintenance Requirements and Actions

For more information about Stormwater Retrofit Monitoring in the Echo Lake Drainage Basin, please contact Carly Greyell, Project Manager, Science and Technical Support Section.