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Characterization of Runoff Quality from Paved Low-Volume Roads and Optimization of Treatment Methods

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Status:  Complete
Report Date:  10/07/2020


Whenever MnDOT or local agencies add a linear acre of new or improved roadway (impervious surface), they are required by the Minnesota Pollution Control Agency to capture and retain stormwater runoff through an approved treatment. Local agencies have known that the treatments are based upon the contaminants found in runoff from high-volume urban highways—roads with tens of thousands of vehicles passing per day. Most rural roads have low traffic volume—some as low as 200 vehicles per day. This project sampled road runoff from 10 rural sites over two years and tested the runoff for contaminants. Results showed that rural roads contain less pollution than high-volume urban roads. The ditches with swales that are often already used along the roads are very effective in treating the runoff. County engineers will be able to use the study’s data for their future stormwater permits.

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