In addition to doing illicit discharge inspections during dry weather, monitoring storm sewer outfalls during snow melt and rain events can reveal pollutants that accumulate and mobilize only when storm water flows through the system.

 Construction site runoff.

Construction site runoff.

Construction site runoff and oil/fuel can be detected at storm sewer outfalls through visual observation. Construction site runoff will often have the same color as the soils being moved on site – it can be reddish to dark gray to chocolate milk-colored or something in between.  Oil and fuel will often float at the surface of the creek, lake, or wetland in a rainbow-colored plume or trail.  These discharges can be traced upstream by comparing the storm sewer system map with the list of permitted construction sites or a land use map showing where fueling or maintenance areas would likely be located. 

Other discharges can be harder to trace and resolve.  Coolant or other additives that leak into the ground at industrial sites may remain in place, undetected until high groundwater from heavy rains mobilizes the material into the nearest underground storm pipe or trench. The storm sewer system map will come in handy to investigate the source of this discharge, as manholes will be opened up and camera work or smoke/dye testing may be needed to pinpoint the source of the problem. 

 Storm sewer discharge after rain event.

Storm sewer discharge after rain event.

Accumulated sediment and solids that turn snow piles black might reach the nearest river or creek when temperatures warm up to melt the snow.  Photographs of these discharges can help document the problem, direct the investigation into the appropriate drainage area and land uses, and also illustrate the problems of storm water runoff to decision makers and the public.

For other ideas on how to incorporate storm sewer system mapping, permit data bases, land use maps, and other tools to enhance the storm water management program, contact an expert today.


About the Authors

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Maureen A. McBroom
Environmental Coordinator

Maureen is dedicated to the protection and improvement of Wisconsin’s resources through close collaboration with municipalities and their citizens.  Efficient & effective implementation, driven by strong relationships and communication, are drivers behind her project implementation strategies.  She has experience in the WDNR’s Runoff Program, specifically issuing WPDES Permit coverage for construction site erosion control & long-term storm water plans, industrial storm water sites and municipal separate storm sewer system (MS4) permittees. Maureen has been with R/M since 2015.

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