Stormwater practitioners spend significant dollars to reduce phosphorus loading to lakes, rivers and wetlands. Though we’ve seen some improvement in water quality, progress has been slow.

Historically we have used total phosphorus (TP) to guide stormwater management. TMDLs, Minimal Impact Design Standards (MIDS) performance goals, and water quality standards, to name a few, all use TP as the metric. But not all phosphorus was created equal. Dissolved forms are about 5 times more bioavailable to algae than particulate forms and can account for up to half of TP in stormwater. Despite this, most of our efforts at reducing phosphorus have focused on particulate forms. Wet ponds, sand filters, rain gardens, swales and other BMPs were initially designed to capture sediment. It shouldn’t be surprising then, that many of our BMPs are underperforming in terms of phosphorus removal.

Efforts are underway to change this. Some examples include the following, along with recommended links.

• Research shows that organic debris, such as leaf litter, is an important source of dissolved phosphorus. Using data collected and analyzed by University of Minnesota researchers (link), credits for street sweeping are being developed and will be available this spring, along with guidance on best practices for street sweeping, available this summer (link).
• U of M researchers are focusing on identifying engineered media, used in biofiltration practices for example, that retain phosphorus (link). The Stormwater Manual contains supporting information on engineered media (link).
• Work continues on identifying phosphorus dynamics in wet ponds with the goal of developing guidance to better design ponds for retaining phosphorus (Manual link; U of M link).
• Data continues to be gathered on iron enhanced systems in an effort to improve existing guidance for design and maintenance of these practices. Look for more on this in the coming months.

Stormwater infiltration, and low impact development (LID) and Green Infrastructure (GI), in general, offer excellent solutions to managing phosphorus. The Manual contains good information on infiltration (link). We are building information on GI into the Manual and have constructed a page that will be populated in the coming months (link). If interested in reading more about phosphorus, a good place to start is this page in the Minnesota Stormwater Manual.

Where feasible, we strongly advocate incorporation of vegetation into stormwater best management practices (BMPs). Vegetation improves hydrologic and pollutant removal performance, intercepts rainfall, reduces erosion and soil media clogging, and promotes evapotranspiration (Muerdter et al., 2018, DOI:10.1039/C7EW00511C). Additional benefits may include, but are not limited to, increased or improved pollinator habitat, climate resiliency, heat reduction, aesthetics, and even goose suppression for constructed ponds.

There are situations where BMPs, also called stormwater control measures, cannot or should not include vegetation. For example, it is often difficult to incorporate vegetation into BMPs in ultra-urban environments. In many of these environments, however, vegetation can be utilized. Examples include the use of tree trenches, subsurface biofilters, and green roofs.

In the coming months, we will be working to improve vegetation information in the Minnesota Stormwater Manual. If you are interested in participating or tracking this work, please contact Mike Trojan at mike.trojan@state.mn.us.

The results of seven local, collaborative, multi-year field-based stormwater research project partnerships are currently being compiled to develop performance reports for three groups of practices: large underground and surficial infiltration systems (water quality), iron-enhanced filtration systems (water quality), and roadside swales (hydrology). Results of these projects may be used to update MPCA guidance for these stormwater control measures. Look for release of these reports throughout 2021.

Also, check out this recent stormwater research article in Science on the cause of Coho salmon die-offs in the Pacific Northwest. This article is the most recent in a series by this research group, who previously identified little-known organic chemicals related to tire wear in highway runoff as the main cause of the fish kills. Previously, however, the runoff’s chemical complexity had inhibited specific chemical identifications. Now, using some admirable sleuthing and refined laboratory methods, the researchers have identified a previously unknown chemical (6PPD-quinone) as the primary cause of the salmon kills. 6PPD-quinone is a transformation product of 6PPD, which is present globally as an antioxidant used to promote tire longevity. These results may indicate the need for regulatory, treatment, source control, and/or green chemistry alternatives for 6PPD. They also suggest a broader need for more careful human and ecological health assessments of transformation products of high production volume commercial chemicals that may be discharged to our environment. If you are unable to access the full article online, please feel free to request it from MPCA’s stormwater research scientist David Fairbairn.

Tons of salt are used every year in Minnesota for managing snow and ice. Salt damages infrastructure and vegetation, and pollutes our valuable lakes, streams, wetlands and groundwater.

Public and private property managers, those who manage or hire snow removal, public and private winter maintenance professionals, and environmental professionals have learned how to apply less salt safely while improving operations by taking one of four MPCA’s Smart Salting Certification Trainings online. Hear from past participants about the benefits of attending training: Get Smart Salting certified.

MPCA Smart Salting Certifications offered:

• Parking Lots & Sidewalks - For private winter maintenance companies, city parks, hospitals and colleges.
• Property Management – For public and private property managers and owners, those who hire winter maintenance contractors, MS4 permit staff, environmental professionals, business owners, and local decision-makers.
• Roads - For city, county, or state plow drivers.
• Level 2 Smart Salting Assessment tool – For public works managers, supervisors, business owners, superintendents, and other lead staff with knowledge of organizational salt application product use and practices. The online Smart Salting Assessment tool – filled with 180 best management practices, offers a calculator for monitoring and projecting potential salt reduction and cost savings.

Why attend?  

• Learn about the new permit requirements in the recently reissued MS4 General Permit that requires specific chloride reduction activities for permittees. Visit the MPCA water permit holders and chloride website for details.
• More efficient operations – Improve your winter maintenance practices.
• Save money and time – Reduce salt use and annual infrastructure damage costs.
• Salt and snow storage improvements – Rethink usual habits and reduce salt runoff.Protect our water resources – Learn the environmental effects of chloride in our valuable water resources.

The MPCA plans to have many opportunities for attendees to register this year. Discover trainings, get certified and listed, as well as identify other smart salting certified professionals near you here.

You may want to register for an online training hosted by a local organization near you, offering the chance to connect to local chloride reduction advocates or host your own private class.