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https://www.nationalacademies.org/trb/events

Leveraging Existing Vegetated Roadside Areas for Efficient Stormwater Management

Stormwater runoff from transportation infrastructure presents a persistent challenge for Oregon’s transportation system due to the requirement to treat highway stormwater runoff and protect downstream water quality. Current regulatory requirements compel project teams to demonstrate adequate stormwater treatment and infiltration performance during planning and design. However, limited understanding of how hydrologic data and roadside soil properties influence geochemical treatment capacity often prevents reliable evaluation of whether the natural roadside environment itself can meet objectives, providing an unrealized opportunity for potential savings on unnecessary facility installation and maintenance costs. OBJECTIVES: The overall objective of this project is to develop and validate an integrated hydrologic-geochemical decision-support tool that enables early-stage screening of existing roadside stormwater infiltration potential and treatment performance. The tool will provide Oregon Department of Transportation (ODOT) with simulation capabilities to predict and quantify surface runoff routing, infiltration capacity, and subsurface geochemical dynamics. The coupled hydrologic-geochemical framework will support quantitative evaluation of whether already existing roadside environments can meet stormwater performance metrics and identify locations where built treatment facilities are actually necessary. The project will provide ODOT with quantitative decision-support framework for early-stage screening of roadside stormwater infiltration and treatment feasibility. The framework directly addresses the current uncertainty in determining when existing roadside soils and vegetative cover can meet stormwater performance requirements and when engineered treatment facilities are necessary. By enabling systematic identification of locations where existing soils provide sufficient infiltration and contaminant attenuation, this project may assist with (1) reducing unnecessary engineered stormwater treatment facilities that require construction costs, operational costs and long-term maintenance commitments, and (2) reducing the need to acquire additional ROW to install engineered facilities, minimizing both project delivery and O&M costs. Even if additional ROW may be needed to fit the natural areas for treatment, long-term operation and maintenance costs will likely be reduced.