Environmental Engineering Reference
In-Depth Information
Brownfi elds
A
brownfi eld
is defi ned in the United States as land that has been previ-
ously used for industrial or commercial purposes and is contaminated
by low concentrations of hazardous waste, but has the potential to be
reused once it has been cleaned up. The land is not compromised severely
enough to be a Superfund site. For example, a site classed as a brownfi eld
may have been occupied by a dry cleaning establishment, an agricultural
supply business, a paint store, or a gas station. Contaminants in the soil
or subsurface at such locations may be solvents, pesticides, heavy metals,
hydrocarbons, or asbestos. If the levels of subsurface contaminants are
too high, brownfi eld land might sit unused for decades before someone
believes it is possible to clean the property economically for a proposed
use. The dividing line between a brownfi eld site and a Superfund site
may not always be clear.
Remediation of a brownfi eld site may use bioremediation, using
naturally occurring microbes in soils and groundwater to expedite the
cleanup. Alternatively, phytoremediation may be useful. Plants that natu-
rally accumulate heavy metals are artifi cially rooted in contaminated
soil. The plants are later removed and disposed of as hazardous waste.
Another method is in situ oxidation, that is, using oxidant chemicals to
enhance the cleanup. Such methods typically require years to be effec-
tive. The technique used depends, of course, on the nature of the
contaminant.
In 2009, 425,000 brownfi eld sites awaited redevelopment.
22
More
than 150 cities had successfully redeveloped 922 brownfi eld sites, return-
ing more than 10,000 acres to economic productivity. Impediments to
brownfi eld redevelopment include shortages of cleanup funds, liability
issues, and the need for environmental assessments. As cities expand and
pristine land for development becomes scarce, remediation of brownfi eld
land is becoming more popular.
Incineration
Incinerators cost several hundred million dollars to build and last for
twenty-fi ve to thirty years. They are safe and effective, but because of
public opposition and their high cost, none have been built since 1997.
There are 113 trash-burning power plants in the United States, and
almost all were built at least fi fteen years ago. Eighty-seven of them are
used to generate electricity. Twenty-two are permitted to incinerate haz-
ardous waste. The older ones in operation are known to create health
