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Green Remediation Strategies: Environmental Caps

Engineered geo-synthetic environmental cap being installed over impacted soils. Picture courtesy of York Housing Authority.

Brownfield redevelopment by its very nature is sustainable. It’s built on the same principle of recycling and reusing consumer goods, such as aluminum cans or reusable water bottles. Instead of consuming valuable open space and prime farmland, brownfield redevelopment recycles and reuses idle land. Brownfields are typically located in an urban core where the structures are able to tap into existing infrastructure such as public transportation, eliminating the need to build new roads or amenities. Once a brownfield is redeveloped it encourages sustainable patterns of development in the surrounding area. It radiates outward, revitalizing an under served community. At the end of the day, redeveloping a brownfield site can contribute to lessening a building’s carbon footprint, but what about the environmental impact from the cleanup activities employed onsite? The tools and resources sometimes used to cleanup up a site use resources and emit greenhouse gasses. They may seem miniscule when taking into account a building’s overall impact, but they contribute to a structure’s carbon footprint nonetheless. One remediation strategy that is effective and has an enormous impact on reducing a site’s environmental impact is managing contamination onsite through pathway elimination and environmental capping.

Environmental Caps, More than Just a Band Aid

At first glance, it may appear that an environmental cap acts as a band aid, merely covering up the contamination until the site’s next use, but it’s more than just a cover up. The sole purpose of an environmental cap is to safely encapsulate the contaminants on site. An environmental cap effectively prevents the vertical and horizontal migration of contaminants by isolating and keeping the pollutants in place. When necessary, caps prevents water from infiltrating downward and carrying the contaminants to the groundwater. They eliminate surface exposures and prevent stormwater and wind from carrying the contaminants offsite. Caps can be comprised of asphalt, concrete, a geosynthetic membrane, vegetated soils, or compacted clay. If a parking area is already existing or planned on a project using it as an environmental cap can be a great remedial solution. Likewise, dedicated open space is a perfect location for an environmental cap.

Managing contaminated soils onsite alleviates a site’s environmental impact by eliminating the need to excavate and transport the soil to an offsite disposal facility or landfill. This traditional method of disposing and treating contaminated soil offsite consumes large quantities of fossil fuel, generates greenhouse gases and costs a lot of money. The size of the dump truck and the volume of soil there is to haul offsite will determine how many trips it will take to dispose of the contaminated soil. Add the distance to the disposal facility and the carbon emissions can increase significantly, not to mention affecting the cost. Furthermore, safely capping the contaminants in place can help to alleviate pressure off of already overflowing landfills. Contaminants are allowed to degrade naturally without human intervention.

Just like not all recyclables are accepted at every recycling center, managing contaminated soils on site will not work on every site. It will depend on the extent of impact, the types of contaminants, the future use of the site and the type of soils in place. Environmental caps are a very useful remediation method that helps to reduce and control a site’s environmental impact and will often save money up front. When the design, construction and operation of a structure are all taken into account, the consumption of energy and resources used can be staggering. A footprint assessment will help calculate the impact from the environmental remediation and keep your sustainability goals on track. Every step, no matter how small, taken to alleviate the negative environmental impact from development is well worth the effort.

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