Each decision to build a place to live, work or play has an impact on our natural environment as well as our future well-being. Design professionals who value sustainability must consider reducing solid waste, conserving natural resources, enhancing and protecting ecosystems and biodiversity, and improving air and water quality. Smart decisions that allow us to meet our present needs, without affecting the ability of future generations to meet theirs, are the goals of sustainable development.
So what’s a developer to do? Brownfield site rehabilitation is sustainable development – the ultimate in recycling. First and foremost, redeveloping an existing site avoids the development of natural, untouched sites or greenfields, uses existing infrastructure and revitalizes a neighborhood or community. Existing site conditions that include contamination, excess soil and rock, land clearing and building demolition debris, can be managed with sustainability in mind. Considering how these materials, often considered wastes, are managed, reused and recycled rather than just disposed of, is sustainable thinking.
Because owners and designers often aim to get their buildings LEED (Leadership in Energy and Environmental Design) certified, the materials and resources, including the choice of building materials and how site waste is managed, are integral to the certification process. Reusing a Brownfields site generates a LEED Sustainable Sites credit, making this an attractive option with a built-in incentive.
Managing Soil
The development of new projects often requires the excavation and off-site disposal of excess soil or rock, sometimes requiring that new clean fill be brought in. Now, we must think of managing these site conditions with sustainability in mind.
Consider leaving contamination in place and encapsulating it beneath a building when faced with at a contaminated site, rather than excavating soils and transporting them off-site for disposal. This may require placing a deed restriction on the property and including a vapor barrier beneath the building. However, there are significant sustainable benefits to this approach. One benefit is that clean fill won’t need to be brought in to replace the excavated contaminated soils, which in turn conserves that raw resource. The environmental costs associated with transport such as fuel consumption is avoided for both hauling the dirty dirt away and trucking in the new clean fill. If a basement or underground parking structure prevents contaminated soils from being left in place, the soils can often be recycled at an asphalt batch plant rather than being disposed of in a landfill. Again this strategy has sustainable benefits because it not only serves as the raw material for creating a new product, but also avoids filling precious landfill capacity to dispose of the contaminated soils.
Site development often requires excavation of historic fill, which may be contaminated with low concentrations of metals, polyaromatic hydrocarbons and petroleum. Excavating for basements and underground parking garages, installing stormwater management structures, or utilities often generates this excess material. Rather than disposing of this material off-site, strategies may be employed to reuse it on-site by rethinking site grading plans. Although this type of excess soil is typically reused as landfill cover, rather than disposed of in the landfill, sustainable thinking requires that we consider other alternatives. Perhaps the soil can be used as fill at a nearby construction site – again avoiding the use of virgin raw materials as fill or filling up landfill cover capacity. Also, fuel costs for transportation can be minimized by taking the soil to a nearby site, thereby avoiding disposal tipping fees.
Even at brownfields sites, often clean excess soil is excavated, requiring off-site disposal. The construction of underground parking, which avoids using land area solely for surface parking and its associated impermeable paving, may generate raw materials that can be re-used. Clean sands or rock may be removed at a site to accommodate building plans. These materials can be used on-site as locally manufactured and processed materials in lieu of imported materials. An example is when bedrock is crushed on-site and then used in roadbeds. This sustainable practice uses local materials, reduces transportation, and supports the local economy. Employing this method may contribute to a LEED Materials and Resources credit for regional materials.
Construction Debris
Materials from the demolition of existing structures on brownfield sites can also be managed with sustainability in mind. The United States Environmental Protection Agency estimates that approximately 136 million tons of construction and demolition debris was generated in 1996. The Massachusetts Department of Environmental Protection regulates asphalt pavement, brick and concrete rubble, such as the rubble generated by the demolition of buildings, bridges or roadways, to encourage its recycle and reuse. The waste ban also conserves disposal capacity, and reduces adverse environmental impacts from waste materials containing toxic substances.
Asphalt, brick and concrete rubble are banned from disposal at solid waste facilities and cannot be disposed of at landfills or incinerators. Materials from buildings, such as brick and concrete, can be crushed and reused in asphalt production, as a substitute for stone or aggregate as structural fill on construction projects. It can often be crushed where it is generated and then reused on-site. Asphalt pavement from parking lots and roads can be reclaimed and reused. The sustainable management of this rubble may contribute to a LEED Materials and Resources credit for construction waste-management.
There are many benefits to managing soils and construction debris for sustainability. Owners can avoid the environmental costs associated with off-site disposal. These costs, both direct and indirect, include landfill disposal (tipping fees), transportation (gasoline), landfill capacity and the risk of the soil mismanagement once it leaves the site.
Using materials that are readily available on-site reduces the amount of new materials that need to be purchased, which further reduces costs. Additionally, these practices may result in LEED points that can make the difference between a building that is certified and one that is not.
Managing the materials that we often think of as waste, from both the underground excavation as well as from building demolition, through recycling, reusing, and reducing the amount of new materials required results in sustainable practices – start thinking of these practices as a way to contribute to a sustainable environment.
