AWRA-WA September Seattle Dinner Meeting

  • 26 Sep 2017
  • 5:30 PM - 8:00 PM
  • Pyramid Brewery 1201 First Avenue South Seattle, WA  98134
  • 34


  • For current WAAWRA members.

Registration is closed
The American Water Resources Association Washington Section

 invites you to

Ten Years of Clean Water:  The Effects of Stormwater Source Controls
on Sediment Quality in Thea Foss Waterway, Tacoma, Washington

 presented by

Dana de Leon, professional engineer at the City of Tacoma,
Environmental Services/ Science & Engineering Division
Mary Henley, senior engineer at the City of Tacoma, Environmental
Services/ Science & Engineering Division


 Tuesday, September 26, 2017


Pyramid Brewery
1201 First Avenue South
Seattle, WA  98134

 Social and Networking - 5:30 PM to 6:30 PM
Dinner - 6:30 PM to 7:00 PM
Presentation - 7:00 PM to 8:00 PM


Under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also referred to as Superfund, contaminated bottom sediments were remediated in the Thea Foss and Wheeler-Osgood Waterways in Tacoma, Washington under the oversight of the Environmental Protection Agency (EPA) at a cost of $105M.  Sources of Contaminants of Concern (COCs) continue to exist in the drainage basins and are conveyed to the waterways via stormwater (municipal and private), aerial deposition, marinas, and groundwater discharges. 

Since stormwater is one of the potential sources, the City of Tacoma is implementing a stormwater source control program (started in 2001) to protect the quality of waterway sediments and the integrity of the cleanup.  The program is supported by post-construction sediment quality monitoring; stormwater, base flow, and storm sediment monitoring; and a validated contaminant transport model of the waterway (EPA WASP model).  Contaminants of concern in waterway sediments include polycyclic aromatic hydrocarbons (PAHs) and bis(2-ethylhexyl)phthalate (DEHP).  These contaminants are associated with various ongoing sources including municipal stormwater, marinas, atmospheric deposition, and groundwater discharges, many of which are common or ubiquitous in modern urban environments.  The WASP model predictions in Thea Foss Waterway show excellent agreement with seven years of observed post-construction sediment quality data, validating the ability of the model to link pollutant loads to sediment concentrations, and predict the effects of source control actions on waterway sediment quality. 

The City’s multi-pronged stormwater source control program consists of best management practices, business inspections, public education, source tracing investigations, and stormwater treatment.  Over the 15 year period (August 2001-September 2016), these efforts have resulted in statistically significant reductions in suspended sediments, lead, zinc, PAHs, and DEHP, in spite of the inherently high variability of stormwater data.  In recent years, the City performed basin-wide street sweeping and system-wide storm sewer cleaning in selected drainages to remove residual contaminated sediments that may continue to degrade stormwater quality. Street Sweeping and system-wide sewer cleaning resulted in statistically significant reductions in PAHs and metals.  Finally, the City developed a GIS-based pollutant loading model of its urban drainages (HSPF model) to evaluate the cost-effectiveness of various treatment technologies and management practices for reducing pollutant loads in stormwater; including in-line treatment vaults, street sweeping, and low-impact development (LID).  The model results identify areas and land uses that contribute disproportionately to stormwater pollution, where source control efforts are best focused, and recommendations for cost-effective source control investments.

About the speaker

Dana de Leon is a professional engineer at the City of Tacoma, Environmental Services/ Science & Engineering Division.  She is a chemical engineer with 28 years of experience in stormwater studies related to quality/quantity, source evaluations, NPDES regulatory issues, stormwater treatment technologies and Superfund evaluation and cleanup. Recent experience includes: 

o Developing regional stormwater treatment program and capital improvement projects with a focus on selecting sites for and tracking publically-owned stormwater treatment facilities.

o Project engineer of the Thea Foss Waterway Source Control Strategy Program.


Mary Henley is a senior engineer at the City of Tacoma, Environmental Services/ Science & Engineering Division.  She is a civil engineer with 31 years of experience, primarily working on environmental cleanup projects and regulatory compliance.  She is the project manager of the Thea Foss Waterway Superfund cleanup project and works closely with the associated stormwater source control program.


$30 for current members

$35 for guests

Free for students (Reserved for student members enrolled full-time, as outlined on the  AWRA-WA website,

If you are planning to pay in person at the event, please note that we can only accept payment then in the form of cash or a check.  If you want to pay using PayPal or a credit card, please do so online before the event.

Registration as a guest is available if you are not a member of AWRA-WA.

Cancellation Policy: AWRA-WA will fully refund the registration fee if cancellation notice is received at least 5 days before the event.


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