Research & Innovation

Need statements

NS738: Incorporation of Soil Health Engineered Measures on MnDOT Construction Projects and Resilient Stormwater Management

Problem

Soil health is an emerging topic for Departments of Transportation. CalTrans and Iowa DOT have shown mitigation of soil health along the inslopes will reduce storm water transport, increase pollutant capture, support robust native and non-native vegetative cover for shoulder preservation, and improve resiliency to climatic events. Construction activity often results in severely degraded soil health compounded by normal damaging event such as stockpiling, rupture of root structure, diversity of vegetative covers, compaction, change in porosity and infiltration. Construction has the potential to permanently change biological (loss of soil life), chemical (loss of nitrogen, carbon), and physical (porosity) soil properties. One common observable result of soil health degradation is increased rates of erosion and downstream impacts to surface water even after perennial covers are re-established. Recent research has shown that soil amendments or incorporation of organic waste materials has the potential to restore soil health and improve post-construction vegetative growth by increasing soil structure, microorganism recovery, water holding capacity, heavy metal transformation (retention) and nutrient retention. The long-term effects on soil health by adding organic matter (organic wastes, salvaged peaty soils, peat or compost) and planting deeper rooted native vegetation warrant further study to determine whether biological, chemical, and physical mechanisms can be implemented to create permanent soil health outcomes. Promoting soil health in transportation infrastructure projects has the potential to result in numerous benefits and is applicable statewide in both urban and rural settings. Soil health also contributes to “Green Infrastructure” (design that incorporates hard and soft infrastructure multiple society function) stormwater functions and has also been shown to sequester carbon, mitigate pollutants and potentially offset climate change impacts.

The goal of this research is to define preconstruction baselines of soil health from reference locations, determine optimized design and field implementation options to rapidly return soils to original baseline health indices using the construction process, and how these can benefit transportation requirements and stormwater treatment.

Objective

The research would (1) examine the long-term restoration effects on soil health by adding organic matter and soil/root interactions (planting deeper rooted native vegetation) and to determine how soil health improvement relate to long -term sustainability and resilience to weather. The research will also assess changes in soil health to outcomes in stormwater management (water flow, reduction in pollutant transfer). The goal of this research is to determine if first flush off pavements can be mitigated near the source rather than transport to ditches or permanent stormwater facilities. The added benefit is long lasting permanent stormwater treatment facilities by promoting near source capture rather than transport to more difficult areas to maintain. This research seeks to (2) determine if healthy soils can translate into multifunctional slopes and ditches that serve as stormwater treatment zones with structural integrity. (3) Develop a standard way to test for soil health parameters (sometimes called the soil food web).

Previous research

Previous research by MnDOT and LRRB has looked at the benefit of amending soils with compost and other organic materials to improve vegetation establishment and stormwater treatment. Research also looked at potential runoff concerns of using compost and other organic wastes as a soil amendment. The proposed research project will take the next step to evaluate how strategically adding organic matter to soils can not only improve the benefits provided by healthy soils and quick vegetation establishment but also improve integrity of pavement and shoulder transitions, stormwater quality, and Minnesota’s waste stream economy.

• Ongoing research project: Comparison of Compost and Proprietary Soil Amendments for Vegetation Establishment (state.mn.us).
• Re-use of Minnesota waste material in sustainably design soils. Part 2

Expected outcomes

• New or improved technical standard, plan, or specification
• New or improved manual, handbook, guidelines, or training

Expected benefits

The numbers 1 and 2 indicate whether the source of the benefit measurement is from: 

1. A specific research task in your project that supports measuring this particular benefit, or
2. Implementation of the research findings (anticipating positive results)

• Construction Saving: (2)
  • Soil health practices will require some investment on the front end such as compost or other soil amendments to initiate a return to soil health. This investment could benefit future projects due to healthier soils in MnDOT ROW’s making vegetation establishment easier, reduce water transport, and improved vegetation quality as a result of this investment in soil health. The research project will look at the costs of re-setting the biological, chemical and physical requirements for soil health and what the potential returns long-term could be.
• Decrease Lifecycle Costs: (2)
  • There is the potential for soil health practices to decrease the lifecycle costs of stormwater management infrastructure such as treatment/storage ponds by increasing natural capacity for infiltration of water within the road right of ways and conveyance ditches which would take some of the demand off of stormwater treatment facilities. This could be very valuable with the increased storm event frequency and intensity from climate change. This has the potential to improve climate resiliency of the overall roadway stormwater management system.
• Environmental Aspect: (2)
  • Soil health practices have the potential to improve vegetation quality, stormwater treatment and climate resiliency of roadsides. As the total area of greater infiltration increases, there is also the potential for these practices to improve shallow groundwater recharge and water storage for plant use during times of drought. This benefit can be assessed by monitoring vegetative growth rates as well as measuring runoff quantities from areas where soil health practices are implemented. Infiltration rates could be assessed either by monitoring runoff rates from soil health plots and comparing these to control sites as well as the potential for measuring infiltration rates using subsurface collection devices.
• Increase Lifecycle: (2)
  • The research has the potential to demonstrate how soil health practices can contribute to healthier vegetation that is more resilient to climate extremes. This research could also demonstrate how a healthy soil vegetation system can be more sustainable and require less inputs for management and an improved right of way that requires less work to establish vegetation on future projects.
• Operation and Maintenance Saving: (2)
  • Soil health systems have been proven in agricultural applications to require less inputs such as fertilizer and watering and the use of native vegetation would require less mowing in portions of the road right of way that do not require mowing for safety.
• User Benefits: (2)
  • MnDOT has considered soil health practices to be a benefit for vegetation establishment/quality and the literature review and past research results has shown the benefits go beyond this and provide benefits for stormwater management, climate resiliency and carbon sequestration.
• Risk Management: (2)
  • Soil health practices can contribute to stormwater management and take some of the demand off ponds and other stormwater infiltration features and decrease the potential for large storm events to result in damage to stormwater management infrastructure.

Technical advisory panel

• David Bauer – Alliant Engineering
• Chris Langlie – MnDOT District 6 Hydraulics or Nick Olson MnDOT Bridge Office Hydraulics
• Mark Guttierrez – Executive Director Minnesota Soil Health Coalition
• Wayne Cords MPCA South Section Watershed Manager (Mankato) and Farmer
• Involved in soil health and stormwater benefits from an agricultural perspective
• Tom Gile – BWSR Resource Conservation Section Manager for Soil Health or Jared House – BWSR Soils Programming Coordinator
• Matthew Summers – Moore Engineering (Soil Health Advocate)