Battelle's ETC2 Facilitates Modernization of EPA's
Storm Water Management Model

In 1971, the U.S. Environmental Protection Agency (EPA), which had recently been established by the Nixon administration, introduced the Storm Water Management Model (SWMM, pronounced "swim") computer software. After 30 years of dramatic changes in the computer and software industry, SWMM remains the industry standard for storm water modeling and has thousands of users.

SWMM is used to model the movement of precipitation through four "layers": atmosphere, land area, groundwater, and transport. The modeling process begins with the atmosphere from which precipitation falls onto the land. The land area module receives rainfall data and models the flow into groundwater, transport and storage, and outflow. The model provides information that managers need to address important environmental issues, including stormwater runoff, combined sewer overflow, and other drainage systems flow issues. Although the original SWMM model has been improved substantially over the years as a result of partnerships between EPA and the private sector, EPA recently decided to collaborate with industry to modernize the model by rewriting the 50,000 lines of patchwork FORTRAN code into C++, using an object-oriented programming approach. New features, including an interface to run under Windows® and industry standard formats to allow interface with geographical information systems and computer-aided design software will be added.

Battelle's Environmental Technology Commercialization Center (ETC2) has facilitated two Cooperative Research and Development Agreements (CRADAs) between EPA and Camp, Dresser and McKee (CDM) to improve the model and software. CDM, a global consulting, engineering, construction, and operations firm, was part of the development team that helped create SWMM three decades ago. The cooperative work includes development of a reliable C++ coded version of the SWMM computational engine that can be run alone or as a dynamic link library of functions, and a GUI (graphical user interface) shell to allow it to run under Windows. A user's manual will also be developed. Under the second CRADA, CDM and EPA are developing a generalized tool for computing inflow hydrographs at a sewer junction; writing code to link inflow hydrographs to the EXTRAN model; developing a Windows-based control system; and preparing a technical guide. A panel of technical experts will ensure that the tools developed have national application and documentation that is technically sound and clear. When the revision is completed in about two years, the improved SWMM software will benefit stormwater modelers nationwide.

For more information, contact Harry Stone at (513) 362-2602, stoneh@battelle.org.