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Communities of Concern

Research Project:
A Sustainable Snow-Free Pavement to Mitigate the Negative Effect of Road Salts on Soil and Water Environment

University: University of Lousiville

Principal Investigator(s): Omid Ghasemi-Fare, Zhihui Sun

Project Description:

Extreme weather in winter, characterized by prolonged and severe conditions, is anticipated soon due to climate change. Consequently, the utilization of deicing chemicals such as salts (including Chloride-based, Formate-based, and Acetate solutions) is inevitable. These chemicals are employed to ensure driving safety and minimize fatal accidents, particularly on critical infrastructure like bridges, highway ramps, and transportation corridors. However, the introduction of chemical solutions into surface runoff, with subsequent infiltration into groundwater, poses significant environmental challenges. This phenomenon can have adverse effects on both soil and water ecosystems, potentially accelerating water eutrophication. Long-term road salt application leads to elevated chloride concentration in groundwater, rivers, lakes, and freshwater bodies, which disrupts aquatic ecosystems. Additionally, sodium chloride (NaCl) impacts abiotic processes in soil and water. A recent study conducted in New York highlighted the impacts of road salts on private wells in the Town of Orleans, New York State. Moreover, road salts can alter soil structures and influence biotic communities. Therefore, it is imperative to explore alternative pavement de-icing methods to mitigate soil and water contamination.

This project aims to reduce chloride pollution in soil and water ecosystem with the use of active (circulating heat carrier fluid) or passive (use of higher thermal conductive elements) geothermal system. Shallow geothermal energy presents a viable solution for pavement de-icing, promoting safety while eliminating the environmental concerns associated with chemical deicers. In the case of active geothermal systems, heat exchanger tubes can be embedded within the concrete pavement to effectively de-ice the surface. Additionally, the project will investigate an innovative passive system that leverages geothermal energy to prevent ice accumulation on the pavement surface. The passive approach involves the installation of solid heat exchangers composed of materials with high thermal conductivity, deep within the soil (20 to 30 feet) to transfer geothermal heat to the surface (please see Figure 1). Both active and passive geothermal systems offer alternatives to chemical usage, particularly road salts, thus preventing soil and water contamination. By embracing these geothermal solutions, the project aims to revolutionize pavement de-icing practices while safeguarding the environment.

US DOT Priorities:

By exploring alternative pavement de-icing methods using active or passive geothermal systems, this project offers a breakthrough in eliminating the environmental concerns associated with chemical deicers. Active geothermal systems embedded within concrete pavement and passive systems using high thermal conductive elements deep within the soil aim to revolutionize pavement de-icing practices, preventing soil and water contamination and promoting environmental sustainability. This research also advances infrastructure durability and resilience by providing innovative solutions in the face of changing weather patterns due to climate change while preserving the environment.

Figure 1: The schematic and example of the Sustainable Snow-Free Pavement using a geothermal system

Outputs:

It is widely accepted that using road salts (such as NaCl, MgCl2, CaCl2, CaxMgy(CH3COO)2(x+y), CH3CO2K, etc.) can contaminate soil and water thus negatively affecting the ecosystem. This proposed sustainable pavement system eliminates the use of road de-icing salts. It can significantly reduce freeze-thaw cycles to extend the service life of concrete pavement. In addition, the geothermal system can control pavement temperature on hot summer days to prevent expansion and thermal cracking. This research introduces a sustainable pavement that utilizes renewable energy to heat and cool pavement surfaces to prevent soil and groundwater pollution caused by chemicals. This system can be installed in many underserved areas and remote sites that are difficult for DOT crews to reach for snow removal. The research findings will be disseminated through peer-reviewed journal and conference publications, and teaching modules for undergraduate students.

Outcomes/Impacts:

The proposed research can significantly help to prevent soil and groundwater contamination, reduce the negative effect on private wells and fresh water, and mitigate the biogenic meromixis that could happen as a result of road salts. Furthermore, reducing the use of road salts helps to keep the soil structure intact and would not change the biodiversity of aquatic animals and plants. The proposed system will also enhance the safety of drivers and motorists during winter, significantly reducing accidents caused by slippery roads and bridges. Figure 2 presents the outcomes and impacts of the proposed project.

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