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November 2007
Stormwater research to influence state, national standards
Findings from University research into the effectiveness of stormwater management devices are influencing state and national standards. The research is led by Omid Mohseni, associate director of applied research at the St. Anthony Falls Laboratory (SAFL) on the Minneapolis campus. Mohseni described his recent work at an October 2 CTS Research Seminar.
Various levels of government spend millions of dollars on stormwater treatment, Mohseni said, but guidelines to evaluate the effectiveness of the devices have been lacking. Third-party lab testing has been limited, and the results of monitoring in previous studies varied widely— up to 500 percent for some devices.
In 2005, SAFL received funding from the Minnesota Local Road Research Board and the Twin Cities Metropolitan Council to conduct field tests on four underground stormwater treatment devices in the metro area. In these tests, the researchers fed several sediment gradations (sizes) into the system at predefined concentrations and flow rates over a specified period of time. The sediment collected in the systems was then filtered, dried, and weighed to determine the true removal efficiency of each structure.
Mohseni and co-investigator John Gulliver, professor and former civil engineering department head, developed a new assessment procedure during their research. A city, for example, could set a target of removing 75 percent of specific particles, then use the procedure to choose the appropriate device, model, and size. The new procedure was incorporated into the Minnesota Stormwater Best Management Practices (BMP) Performance Assessment Protocol through funding from the Minnesota Pollution Control Agency (see www.pca.state.mn.us).
“Manufacturers are happy with the research…and are promoting it across the country and to Canada to encourage adoption,” Mohseni added.
In a follow-up project funded by the LRRB and Mn/DOT, Mohseni and Gulliver are assessing how underground stormwater treatment devices perform under high flow conditions such as severe storms. The results will also be integrated into the Stormwater BMP Assessment Protocol.
The research has received national recognition. Mohseni was invited to become a member of an American Society for Testing and Materials (ASTM) subcommittee that is developing a standard method for evaluating proprietary devices. He was assigned to a four-member task group that is preparing a first draft, due in December 2007, which will be submitted to the full subcommittee. “It is very likely that the method developed through this project becomes the standard method nationwide,” he said.
Earlier this year, Mohseni and Gulliver were assigned to chair the lab testing and scaling subcommittees, respectively, of the American Society of Civil Engineers (ASCE) Environmental and Water Resources Institute Task Committee on Guidelines for Certification of Manufactured Stormwater BMPs. The task committee is developing guidelines for evaluating proprietary underground devices.
In related news, a new stream restoration/ bioengineering facility is under construction at the St. Anthony Falls Laboratory called the Outdoor StreamLab (OSL). The facility evolved from an earlier Mn/DOT-funded project, Scoping Study for the Development of Design Guidelines for Bioengineering in the Upper Midwest (report # 2004-47). Funded by SAFL and the National Center for Earth-surface Dynamics (NCED), OSL will be used to investigate some of the fundamental processes and mechanisms involved in soil bioengineering techniques—which are widely used to protect slopes and river banks against erosion—as well as stream restoration and river morphology.
To read more about Mohseni’s and Gulliver’s research, please visit www.cts.umn.edu/research.