VELMA model green infrastructure applications for reducing 6PPD-quinone concentrations in Puget Sound urban streams
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This research builds upon successful StRAP 3 (Appendix B) and RARE project tests of ORD's VELMA ecohydrology model to identify urban GI solutions for reducing stormwater contaminant loads impacting ESA-listed salmonids in the Puget Sound National Estuary. For example, recent results (McKane et al. 2021, Halama et al. 2022) demonstrate VELMA's capabilities for accurately modeling urban stormwater peak and low flow events and associated fate and transport of a ubiquitous tire-rubber derived contaminant (6PPD-quinone) recently proven to be responsible for killing coho salmon before they can spawn in urban streams draining to Puget Sound (Tian et al. 2021).
VELMA's high-resolution (5-meter) linkage of hydrological and biogeochemical processes within urban watersheds supports fate and transport analyses and spatiotemporal animations designed to clearly communicate the effectiveness of alternative GI treatments for limiting transport of contaminants such as 6PPD-quinone to streams and estuaries. Key outputs include mapped contaminant transport hotspots within watersheds that community stormwater managers can use to optimally locate GI treatments – raingardens, bioswales, pervious pavements, etc. – for limiting transport along primary flow paths to stormwater drains and pipes that expedite chemical transfers to water bodies.
This StRAP 4 research will leverage abundant (gigabytes) urban infrastructure and water quality data being provided by community, state, tribal, EPA Region 10 and other partners to scale up VELMA GI assessments for high-priority Puget Sound near-shore urban watersheds (Peter, Lundin et al. 2022) for a portfolio of contaminants of concern threatening ESA-listed salmonids and orca (6PPD-quinone, PCBs, PBDE, PAHs, fire retardant, agricultural pesticides, etc.).
An overall aim of this sub-product is to use VELMA results to develop simple rules of thumb for when, where, what kinds, and how much GI is required to reduce stormwater pollutant loads under different conditions. Those rules-of-thumb will be most useful/convincing for stormwater managers and policy makers if modelers and empiricists work together on verification and regional extrapolation aspects. For example, our Washington Department of Ecology Stormwater Workgroup partners include a coalition of >300 regional stormwater scientists and managers well engaged in such efforts. Our shared goal is to provide stormwater managers and policy makers with verifiable, model-based decision support that addresses stormwater quality and quantity responses to GI in the face of changing climate and land use conditions.