Gross Solids in Stormwater and the Associated Nutrient Loading

Abstract Submission: Trees and other vegetation in cities have many environmental benefits yet coarse organic material derived from vegetation has been found to contribute to nutrient pollution to water resources. Additionally, the coarse organic material and gross solids do not appear to be well characterized by traditional stormwater sampling. We collected data from 13 urban watersheds in the Minneapolis/St. Paul metro area over two years and characterized the material collected through mechanical sieving, loss on ignition testing, nutrient analysis, as well as measurement of settling characteristics of the organic material in an attempt to better understand how the coarse organics material and gross solids are contributing to water resource impairments. Our results show that nutrient inputs to water resources are not entirely understood or accounted for unless they include a measure of the coarse solids and coarse organic matter being deposited from the contributing watershed. This appears to require different sampling techniques or modeling to fully account for vegetation derived material in many areas.

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