The Remediation Roster
The primary players in brownfield redevelopment include the property owner and a real estate or specialized environmental attorney who ensures that the project complies with all applicable laws, including the Brownfield Revitalization Act. Then comes the usual coterie of design talent: architect, landscape architect, civil and geotechnical engineers, consultants for above and below grade—such as a foundation engineer—and the environmental engineer, who will do the heavy lifting of designing the remediation.
Determining whether the site is contaminated is the first step in remediation. Owners seeking EPA assessment and cleanup grants must undergo a process called All Appropriate Inquiries (AAI) that an environmental professional—usually an environmental engineer or scientist—must complete. “They go in, look at a site’s history, and basically ascertain … what the contamination may be,” Bargmann says. “The operative word there is ‘may.’ ”
The process includes interviewing current owners and occupants regarding present and past uses, reviewing historical sources and government records, searching for environmental cleanup liens, and visually inspecting the site and adjoining properties. Following these activities, the redevelopment team should know whether site contamination is a possible concern. The next step involves testing the soil itself, another job of the environmental professional.
Characterizing and monitoring the nature of a site’s contaminants requires technologies running from the straightforward—such as sending soil, soil gas, and groundwater samples to the lab for analysis—to the complex, such as employing gas-chromatograph mass spectrometers to determine what contaminants are present in which media. The litany of possible contaminants includes arsenic, chromium, dense nonaqueous phase liquids (DNAPLs), dioxins, mercury, methyl tertiary butyl ether, persistent organic pollutants, polychlorinated biphenyls, and trichloroethylene. McLaughlin says that the list includes “heavy metals, which people have to contact directly—for example, eaten or breathed as dust—to be harmed” and “volatile contaminants, many of which are present as vapors or gas and can leave the dirt and come into a building on site, much like radon.”
Once a site’s contaminants have been characterized, the environmental professional designs a remediation solution that complies with state and federal environmental regulations. For some types of remediation, prescribed methodologies based on established practice can guide the process. “Brownfields are hardly new,” McLaughlin says. “A lot of states have pretty mature programs to get developers to remediate their sites the smart way—without a massive amount of liability and wasted cost. Just about everybody has redeveloped a gas station or dry cleaner’s, and there are proven ways of dealing with them.”
The most cost-effective solution for contaminants such as heavy metals often is to bury them in situ and cap the site with a building, parking lot, or at least one or two feet of clean soil and plantings. For non-heavy metal contaminants, such as volatile organic compounds (VOCs), an oft-employed solution is to extract and cart away the toxic material to an EPA-approved disposal site.
Bargmann calls these old-standby remediation methods “cap and cover” and “hog and haul.” “You’re only leaving the contamination for the next generation to deal with,” she says. “That could be a good thing because they might be better equipped than we are, but … I’ve been an advocate of bioremediation,” which uses microorganisms and their enzymes to absorb and break down pollutants naturally.
Bioremediation works only on certain contaminants such as VOCs and oils; heavy metals generally cannot be bioremediated. The emerging technology often happens naturally, without any human intervention, but people can nudge the process forward. “We can help nature get rid of compounds through science,” McLaughlin says. “For example, particular biological microbes thrive in anaerobic conditions. If you can turn aerobic subsoil anaerobic, you can make a lot of toxins disappear very quickly. We’re feeding bugs, adding bugs, and doing what we can to help process along.”
Bioremediation technologies include: air sparging, in which air or oxygen injected into contaminated aquifers removes volatile and semivolatile organic contaminants by essentially evaporating them; and bioventing or biosparging, in which air is injected into the soil through wells.
Phytoremediation, a close cousin to bioremediation, uses plants to absorb and sequester pollutants—including heavy metals, fertilizers, pesticides, solvents, explosives, and petroleum products—from the soil and groundwater. The plants are then harvested and either used or disposed of in an approved site. Phytoremediation only works in the top layers of the soil and shallow groundwater within reach of the plants’ roots.
Outside of bioremediation, soil-vapor extraction, in which the earth is literally vacuumed to remove volatile and semivolatile compounds, attempts to treat contaminants on site, as does thermal treatment, which exposes the contaminated material, either in situ or ex situ, to high temperatures, thus separating, destroying, or immobilizing the waste.
Other techniques for remediation range from the mundane, such as soil washing, to the cutting edge, such as the use of nanotechnology: scientists can engineer specific nanoscale materials, which have large surface areas compared to their volumes, to react to—and rapidly reduce the concentration of—contaminants.