S8. Monitoring and Assessment

Summary of Program Components

The stormwater monitoring program consists of Regional Status and Trends Monitoring and Stormwater Management Program Effectiveness and Source Identification Studies.  The Permit allows Permittees to either pay into these collective funds or to conduct studies relevant to these topics.  The City has elected to pay into the Regional Status and Trends Monitoring fund and conduct a Stormwater Management Program Effectiveness and Source Identification Study.  This is a continuation of the City’s elections from the 2013 permit cycle.

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. The waterway is currently in the process of being deleted from the National Priorities List as part of the Commencement Bay Superfund site.

The City notified Ecology of the choice to pay into the collective fund for the regional stream status and trends monitoring prior to the December 1, 2019 deadline.  Payments into this collective fund are due on August 15th of each year.

The City notified Ecology of the choice to pay into the collective fund for the regional stream status and trends monitoring prior to the December 1, 2019 deadline.  Payments into this collective fund are due on August 15th of each year.  This program is implemented by Ecology through the Stormwater Action Monitoring Group (SAM).  The City of Tacoma has been implementing a comprehensive monitoring and source control strategy in the Foss Waterway Watershed since 2001. Stormwater monitoring is required to be conducted under a Stormwater Work Plan Addendum to the Thea Foss Waterway Consent Decree (CD) with EPA and currently by Section S8.C of the National Pollutant Discharge Elimination System (NPDES) and State Waste Discharge General Permit for Discharges from Large and Medium Municipal Separate Storm Sewer Systems (Permit), which supersedes previous NPDES requirements.

The City has elected to meet this requirement by continuing to monitor stormwater discharges at seven outfalls to the Thea Foss Waterway.  The City notified Ecology of the choice to monitor the Thea Foss Waterway outfalls prior to the December 1, 2019, deadline.  The Quality Assurance Program Plan for the outfall monitoring was provided for Ecology review prior to the February 1, 2020, deadline, and stormwater sampling began on October 1, 2020, for the 2019 to 2024 permit cycle.  Monitoring results will be reported annually with the NPDES Annual Report due on March 31st of each year. 

As part of the 2022 evaluation, the monitoring report reviews results from over 20 years of outfall monitoring conducted under the Foss Monitoring Program and source control actions completed in the Thea Foss drainage basins. The City completed additional sediment monitoring in the portion of the waterway north of the SR509 Bridge in 2018, and an analysis of this data relative to stormwater concentrations was included in the 2018 report to evaluate the impact of known ongoing urban and marine sources to the waterway.  At this time the waterway appears to have equilibrated with known sources generally at concentrations below levels of concern. The City and others will be monitoring waterway sediments next in 2024 and the 2024 report will include a qualitative analysis of this data. Based on results of the 2018 monitoring and subsequent reporting, EPA determined that requirements have been met, and the remedial action in the waterway is complete. Based on this determination, they are currently in the process of deletion of the Thea Foss Waterway from the National Priorities List as part of the Commencement Bay/Nearshore Tideflats Superfund site.

Click the link to view the entire 2021 monitoring report Thea Foss and Wheeler-Osgood Waterways 2022 Source Control and Water Year 2022 Stormwater Monitoring Report.  A link to the 2023 Thea Foss and Wheeler-Osgood Monitoring Report will be posted in the final SWMP Plan available on March 31, 2024.