How much coarse organic matter is in urban stormwater? Does it matter? Do we even know how to capture it? Large coarse organic solids or gross solids include fine and coarse sand, gravel, trash, coarse organic matter (e.g. leaves, twigs, seeds), and other solids greater than 75 μm (ASCE, 2009.). Gross solids in stormwater present many challenges including how to sample and characterize these components to accurately reflect what is in urban stormwater runoff. Gross solids could be an important source of P to these receiving waters, but their contribution to total P (TP) loads in stormwater runoff is not well understood. To better understand the contribution of gross solids to TP loads, a study was initiated in 2020 that captured and examined gross solids from 13 different urban watersheds in the Twin Cities Metro Area over a two-year period. This study explored new sampling techniques and examined modifications of existing stormwater models to determine how they could be used to estimate coarse organic loadings. Efforts also determined the nutrient content of the course organic material to help better understand the total phosphorous balance in the watershed and provide a better accounting of the phosphorus that could be reaching receiving waters from course organics. The results showed that organic material is present in urban stormwater runoff in surprisingly large amounts and contains a significant amount of phosphorus that needs to be accounted for and managed. This seminar will discuss the results of the study and feature a panel of practitioners to discuss the application of science. This project was financially supported by the Minnesota Stormwater Research Council.
Dr. John A. Chapman is an Associate Research Professor for the University of Minnesota Department of Bioproducts and Biosystems Engineering and also serves as the Director of the Erosion and Stormwater Management Certification Program. John holds a Ph.D. in Civil Engineering from the University of Minnesota, a M.S. Degree in Civil Engineering and a B.S. Degree in Geological Engineering from the University of Wisconsin – Madison. He is a registered engineer in Minnesota and Colorado. When not researching erosion control and stormwater, he conducts workshops for engineers, contractors and other professionals on stormwater management technology and regulations.