Abstract

In order to minimize impacts of urban nonpoint source pollution and associated costs of control (storage and treatment) associated with wet-weather flows (WWFs), stormwater runoff volumes and pollutant loads must be reduced. A number of control strategies and so-called "best management practices" (BMPs) are being used to mitigate runoff volumes and associated nonpoint source (diffuse) pollution due to WWFs and include ponds, bioretention facilities, infiltration trenches, grass swales, filter strips, dry wells, and cisterns. Another control option is popularly termed "low impact development" (LID) - or hydrologic source control - and strives to retain a site's pre-development hydrologic regime, reducing WWF and the associated nonpoint source pollution and treatment needs.

Methodologies are needed to evaluate these BMPs, their effectiveness in attenuating flow and pollutants, and for optimizing their cost/performance since most models only partially simulate BMP processes. Enhanced simulation capabilities will help planners derive the least-cost combination for effectively treating WWFs. There is currently a confusing array of options for analyzing hydrologic regimes and planning for LID. Integrating available BMP and LID processes into one model is highly desirable.

This work analyzes several current modeling methods to evaluate BMP performance with the intention of facilitating the integration of improved BMP modeling methods into the U.S. Environmental Protection Agency (EPA) Storm Water Management Model (SWMM). Several other models are examined as part of this study. Options for enhancement of SWMM's LID simulation capabilities are also presented. Two extensive case studies in Portland, Oregon help to clarify current SWMM capabilities and needs for enhancement. The effort documented in this report is linked to a parallel effort at the University of Colorado related to optimization strategies for WWF control.

Contact

Dennis Lai

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