Ten Years with the Minnesota Stormwater Manual, MIDS, and TMDLs – Some Observations

Despite the best intentions of stormwater practitioners, sometimes things don’t work as hoped or expected. The Minnesota Stormwater Manual, Minimal Impact Design Standards (MIDS), and Total Maximum Daily Loads (TMDLs) are widely used tools and strategies for managing stormwater runoff. This presentation explores how these tools and strategies have missed the mark for the following troublesome issues, and more importantly, how they can be improved.
• Dissolved phosphorus: Historically, we have focused on reducing total phosphorus loads from stormwater runoff to receiving waters. But the main culprit may be dissolved phosphorus, which we have largely ignored in our guidance and regulatory mechanisms.
• Chloride: While the only solution to reducing chloride loads to receiving waters in urban areas is to reduce application of road salt, we can reduce negative impacts by better understanding how chloride moves in the environment, particularly in the context of stormwater infiltration.
• Stormwater treatment systems: Stormwater management has largely focused on design of individual stormwater best management practices (bmps), such as rain gardens and ponds. To maximize the effectiveness of stormwater management, we need a systems approach that encompasses pollution prevention and pretreatment, allows us to choose and build the right bmps, and achieves multiple benefits through integration with green infrastructure.
• TMDLs and modeling: Using models to meet regulatory requirements of TMDLs for stormwater is often misguided, since the focus is often on numeric targets rather than practical approaches.
• Communication and outreach: Good information and tools are of no value if we can’t deliver them to practitioners. This presentation includes some lessons learned for communicating to different audiences.