Iron-Enhanced Swale Ditch Checks for Phosphorus Removal

Status:  Active
Project Start Date:  06/16/2016


Swales and/or drainage ditches for linear road projects have excellent potential for stormwater treatment. They can infiltrate water into the soil, filter sediments and associated pollutants out of the water, and settle solids to the bottom of the swale. Currently, however, there is little information that can be used to gain pollution prevention credits with the Minnesota Pollution Control Agency (MPCA), and meet permit requirements. The proposed research will measure the performance of iron-enhanced check dams in roadside swales as a novel stormwater treatment system developed specifically for capturing phosphate and toxic metals from roadway runoff in both urban and agricultural environments. Permeable check dams enhanced with iron filings have been developed and tested in the laboratory through a project funded by the Local Road Research Board (LRRB), and check dams have been designed and built through a project funded by the MPCA. The long-term effectiveness of these new enhancements is, however, yet to be investigated. This research will 1) document the field performance of iron-enhanced swale check dams for three years, 2) determine the pollutant retention in the filter insert and in the entire check dam, 3) evaluate the long-term Last Revised 8/5/2015 Page 2 of 12 performance of the check dams, and 4) identify maintenance needs for continued successful performance of the check dams. Results from this study can be used to design systems for use along roadways throughout Minnesota and the United States. Results can also be used to estimate load reductions in Total Maximum Daily Load studies for future installations of iron-enhanced swales.

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