MnDOT and local agencies control stormwater runoff from roadways through a range of settlement, filtration and infiltration facilities, such as wet ponds, infiltration basins, trenches and swales. Infiltration facilities have been used for more than 30 years, but a high rate of failure has been tied to inaccurate determination of soil infiltration rates. Researchers developed new tools and protocols to provide designers and engineers with the accurate infiltration measures they need, from initial site selection through construction. These tools and methods will support the development of successful stormwater infiltration facilities along Minnesota roadways.Continue reading Stormwater Bioslope Site Monitoring Continues Using Local Filter Media
This article was originally published in Catalyst, May 2021.
Strategies for managing stormwater runoff have been steadily undergoing a shift in recent decades toward “green” infrastructure. This is a potentially beneficial change, but transportation professionals are beginning to recognize a need for better information on how to properly design, implement, and maintain these facilities.Continue reading A Long-Term Approach to Green Stormwater Infrastructure
A recent study determined the effectiveness of a two-cell iron-enhanced stormwater filtration basin to remove phosphorus from highway stormwater runoff collected from 2012 to 2018. Researchers recommended design changes that would allow for more accurate monitoring of these filter basins.Continue reading Monitoring Performance of an Iron-Enhanced Stormwater Filtration System
This article was originally published in Catalyst, August 2020.
Using “green” infrastructure is a useful strategy for handling city stormwater, which may contain deicers and other contaminants from streets and sidewalks. Choosing the right method and ensuring it doesn’t cause unforeseen damage, however, is another matter.Continue reading Green Stormwater Infrastructure: Tradeoffs and Maintenance
Climate change scenarios have been fairly well-tested and vetted. Moore et al. (2015) found that one of the noteworthy impacts on upper Midwest cities is an increase of storm magnitude of 39% (moderate scenario) to 163% (pessimistic scenario). However, the impact of these scenarios on stormwater infrastructure are not well understood and documented. There are some important financial decisions that need to be made for stormwater infrastructure in the present and near-future, requiring demonstration and discussion of the impacts of climate change on stormwater infrastructure.Continue reading New Project: Climate Change Adaptation of Urban Stormwater Infrastructure
This article was originally published in Catalyst, April 2020.
The Minnesota Department of Transportation (MnDOT) is exploring innovative ways to filter pollutants from stormwater runoff and meet permit requirements for construction projects. In a recent study, U of M researchers documented the performance of an iron-enhanced ditch check filter to remove phosphates from stormwater. They found that the filter was effective, though its performance decreased over time.Continue reading Redesigned iron-enhanced ditch checks could help filter pollutants from stormwater runoff
Researchers determined that natural soil amended with locally sourced materials performed well in bioslopes and bioswales. This practice will allow MnDOT to avoid hauling in costly commercial materials for stormwater management installations.Continue reading Using Regional Materials to Manage Stormwater Runoff
Researchers documented performance of an iron-enhanced ditch check filter to remove phosphorus from stormwater over three years. The filter was effective, but its performance decreased over time, and it will require relatively frequent maintenance. Several design changes may be considered.Continue reading Evaluating Iron-Enhanced Swale Ditch Checks for Phosphorus Removal
Soil carried away in stormwater runoff from road construction sites can pollute lakes and rivers.
Stormwater settling ponds provide a place for this sediment to settle before the water is discharged into local bodies of water. However, since stormwater ponds have limited space, a mechanism is needed to remove clean water from the pond to prevent the overflow of sediment-laden water.
MnDOT-funded researchers have designed temporary stormwater ponds with floating head skimmers that can remove clean water from the surface of the settling pond, using gravity to discharge water into a ditch or receiving body.
This is a new approach for MnDOT and Minnesota cities and counties, so research was needed to provide practical guidance for how to use these devices on construction sites.
“This was a small-scope implementation project for professionals to use as they design temporary stormwater ponds that meet state parameters,” said Dwayne Stenlund, MnDOT Erosion Control Engineering Specialist.
A new MnDOT study identifies five methods for “skimming” stormwater ponds that can improve a pond’s effectiveness by 10 percent. MnDOT researchers also created designs for temporary stormwater ponds on construction sites with the capacity to remove approximately 80 percent of suspended solids.
These designs will help contractors meet federal requirements for stormwater pond dewatering. Researchers also determined how often a pond’s deadpool must be cleaned, based on watershed size and pool dimensions.
“When sediment settles, it’s hard to determine when to clean out a pond. Based on the density of the sediments in the Minnesota River and the loading rates we computed, we were able to calculate how often we need to clean out a pond so sediment doesn’t reach the height of the skimmer,” said Joel Toso, principal of Wenck Associates and a consultant for the project.
Earlier this week, the Minnesota Local Road Research Board released this new video showcasing best practices for local stormwater management. Although it’s primarily a training video for engineers and other public works professionals, non-transportation geeks might also enjoy learning about some of the interesting, innovative techniques being employed in cities and counties across the state.
Those who’d prefer not to watch the whole 14-minute video can skip ahead by clicking on these highlights:
- Woodbury’s stormwater ponds (1:52)
- Washington County’s bioretention gardens (2:56)
- “Green roof” bioretention method (4:02)
- Maplewood’s underground detention system (4:39)
- Greenway stormwater project in Minneapolis (6:03)
- Minnetonka’s hydrodynamic separator treatment system (7:47)
- Arden Hills’ infiltration (swales) system (8:26)
- Shoreview’s permeable pavements (9:52)
- Ramsey-Washington permeable pavement project (11:11)
- Tree boxes/trenches in Ramsey-Washington (12:06)
Overall, the video gives you an appreciation for the incredible amount of planning and work that goes into managing stormwater runoff — a task that’s critical to protecting the state’s waterways from pollution (but which many people no doubt take for granted). For those who want to learn more, the best management practices showcased here are examined in greater detail in a recent LRRB report, “Decision Tree for Stormwater BMPs,” which is available for free on the LRRB and MnDOT Research Sevices websites: