MN Stormwater News -- January 2019

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January 2019

Grand Rapids: Salting smart to protect Minnesota waters

Truck spreading road salt

De-icing salt can travel with snowmelt and rain to surface waters where it only takes one teaspoon of salt to permanently pollute five gallons of water. Salty water harms freshwater fish and other aquatic wildlife.

Communities can reduce their salt use with smart salting strategies such as slowing salt application from salt trucks, calibrating their salt application equipment annually, properly storing salt, and training staff on proper salt application.

The City of Grand Rapids has already taken steps to effectively reduce their winter salt use while maintaining safe driving conditions. We interviewed their Public Works Director Jeff Davies and Stormwater Specialist/snowplow driver Steve Anderson to learn more about their program.

MPCA: Grand Rapids has been implementing some efficient and innovative practices in their winter maintenance program. Could you tell us about them?

Jeff Davies: It starts out with having a snow plowing and ice removal policy, which we have had since 1991. It used to be that when the roads were slippery, we would put salt down and if they were still slippery, we would put even more salt down but times have changed. About 10 years ago, we introduced a sentence in our de-icing portion that it shall be the policy of the city to consider cost and environmental impact from chemical usage as well as the safety of the public when establishing applications rates and locations for application.

We make sure to plow and scrape the roads first so that the amount of chemical used can be reduced which in turn reduces the amount of moisture on the roads to deal with. We don’t wait until we’ve had two inches of snowfall to take action either. We try and get out to apply a pre-treatment product on the roads to help keep them clear. Using brooms on sidewalks and paths has also been an effective method to minimize product use. It’s important to realize that certain de-icing agents will not be effective below certain temperatures. To account for this, we use about five different de-icing products, which will be effective in different situations. We use the Minnesota Snow and Ice Control Field Handbook. The calibration charts based on pavement temperature and weather conditions are useful guidelines. It basically boils down to your labor force, the education of your workers, and their buy-in that they want to reduce salt use. We also have a dedicated Stormwater Specialist, Steve Anderson, who acts as our “watchdog” and is always looking to try out new ideas to improve the program.

MPCA: What are the benefits that you’ve seen from these practices?

Steve Anderson: We’ve always [hauled] out plowed snow from our central business district, which is just adjacent to the Mississippi River. Some might think this is for aesthetic reasons, but when we haul out that snow, we remove a lot of the anti-icing product that we had applied in the area preventing it from discharging into the river once it eventually melts, which has had a positive effect on the river. By conducting an inventory of the city and identifying the most sensitive areas with a high potential to discharge to the public waters, we have been able to prioritize our plowing practices to have a greater impact on our environment. Economically, when we train our staff and update and recalibrate our equipment to deal with the different conditions, we can put a minimal amount of product down and be as effective or more effective than going out there and blasting everything.

Jeff: We have four snowplow trucks, one for each quadrant of town, which are all computer calibrated to take the guesswork out of how much product is being applied.

Steve: Minimal product use is also economically beneficial as over-application can take its toll on infrastructure. A residual salt left for long periods of time on the roads and sidewalk will increase its rate of deterioration.

Jeff: And that’s a good benchmark! If you notice that there’s residual product leftover after a storm, it’s a sign of over-applying. After calibration of our salt use, we have actually been sand-free for years as salt has been a much more effective tool resulting in less clean-up such as sweeping sand off of streets and cleaning it out of catch basins from storm sewers.

MPCA: What are some of the challenges you’ve faced?

Jeff: I’d say number one is when it’s 20 degrees or colder with rain. We seem to get about three or four of those a year but it’s this sleet that leads to really icy condition, where we work longs hours and days to get the ice off. That’s really the benefit of anti-icing. When we get the prediction of cold weather and high moisture, you had better be anti-icing because it really pays off. Ice storms are another of the biggest challenges, and it’s our modernized fleet that really provides help when we need it. They can be expensive, but to have reliable snowplow trucks with minimal failure has been important to our city of 10,000 people.

Steve: I wouldn’t say it’s so much of a challenge, but it’s important to keep the public informed. Public expectations of driving in the winter time are that they want to drive like its summer and 80 degrees out so they want the streets to be bare. That level of expectations is not feasible most of the time. We try to keep the public aware that we’re keeping the streets as good as we can during the winter, and people have to adjust their ways of thinking and driving.

Jeff: Guaranteeing bare pavement is impractical and not a reality unless you’re going to over-salt and use too much product.

MPCA: What are the plans for the future concerning your winter maintenance program?

Jeff: Stay on tops of things. We go to the Road Salt Symposium every year – where there’s 200 to 300 people from MNDOT, all the way down to the townships attending – where we listen and learn! If you’re de-icing and plowing like you were 10 years ago, you’re a dinosaur. You’ve got to continue to learn and try new things.

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Check out more Smart Salting success stories to see the great work being done by Minnesota municipalities. The online Winter Maintenance Assessment tool has 180 best management practices to help winter maintenance professionals minimize their salt use.

Learn about the latest innovations, trends, and best practices for reducing salt use while maintaining safe roads at the 18th Annual Road Salt Symposium, February 7, 2019, at Plymouth Creek Center.


Permit termination requests to be available via e-services

Permit notice of termination (NOT) requests will soon be available via MPCA’s e-Services. Construction stormwater permit holders will be able to log into their accounts to apply for a permit termination. Additional instructions will be provided online when the service is available. During the transition period, the agency will accept either paper termination forms or the e-services application. However, in the future, the online service will be mandatory for permit terminations. A confirmation email will be sent to the applicant once the termination application is received.


New work on reducing phosphorus in stormwater

Algae on the water near a lake shore

More than 200 bodies of water statewide have excess levels of phosphorus. Bioretention, tree-based stormwater control measures, and constructed stormwater ponds effectively remove many stormwater pollutants, but in some cases actually contribute phosphorus to lakes and streams. We are excited about three new projects to address these concerns:

"Developing a street sweeping credit for stormwater phosphorus source reduction" is a recently funded research proposal by the University of Minnesota. Dr. Sarah Hobbie from the U’s Department of Ecology, Evolution, and Behavior is the lead investigator. The project focuses on developing empirical relationships necessary to quantify phosphorus load reductions due to street sweeping. The research objective is to establish relationships between sweeper volume, wet and dry mass of solids, and phosphorus loads across a range of tree canopy covers and species composition. The work supports the work of the MPCA and a team of stakeholders to develop a street-sweeping credit for phosphorus removal. Part of the project is an extensive outreach and communication effort to develop guidance for the Minnesota Stormwater Manual and training materials, webinars, and workshops as appropriate.

“Bioretention media optimization, phosphorus source reduction” is another recently funded research proposal by the University of Minnesota. Dr. Andy Erickson from the U's St. Anthony Falls Laboratory is the lead investigator. Objectives of the study include identifying local, sustainable bioretention media that do not release phosphorus, and documenting local sources, simple tests or metrics, and design specifications for practitioners. This study also includes extensive outreach and communication to develop guidance for the Minnesota Stormwater Manual and webinars, videos, and other materials as appropriate.

An MPCA-sponsored literature review will examine factors that contribute to phosphorus export from constructed stormwater ponds. The review objective is to determine the extent to which various ponds may export phosphorus, identify likely contributing factors, and develop recommendations for pond design, construction, and maintenance to enhance phosphorus removal and retention.

The two research projects extend through June 2020. The two-phase MPCA literature review extends through 2019. For more information, visit the Future updates page in the Minnesota Stormwater Manual. For more information on phosphorus, check out these manual pages:


Using low-impact development to build climate change resilience

Bioinfiltration

Climate change has famously increased the number of intense and high-volume rain and snow events in recent years, and that trend is predicted to continue. Using low-impact development (LID) principles to plan stormwater management and infrastructure can help alleviate the effects of climate change. What does this planning look like, especially when you can't predict the weather changes to come?

The article “Assessment of low impact development for managing stormwater with changing precipitation due to climate change” (Pyke et al. (2011), Landscape and Urban Planning) demonstrated one way to estimate the effects of changing climates for a large area (1,400 ac). The authors used a simple method to estimate proportional changes to runoff and pollutant loads (TSS, TN, TP) to receiving waters under various redevelopment scenarios at a former air force base, applying a model called the Smart Growth Water Assessment Tool for Estimating Runoff (SG WATER). The only variables were changes to impervious surfaces and precipitation volume and intensity.

Sensitivity analysis indicated that impervious cover was the most important modeled variable. This research showed that an LID redevelopment scenario (16% imperviousness, space for ~6000 residents) performed much better than a conventional redevelopment scenario (23% imperviousness, space for ~1500 residents) under all modeled precipitation scenarios. The authors noted that even greater differences would be likely between LID vs. conventional design outcomes, because conventional development would require additional developed areas to support an equal population. The research quantitatively demonstrates that LID outperforms conventional designs based solely on relative imperviousness. It also provides a simple but clear method to estimate the advantages of LID under different climate change-related precipitation scenarios.

Tree trenches in the parking lot at Maplewood Mall

Tree trenches in the parking lot at Maplewood Mall