Environmental Engineering Reference
In-Depth Information
This chapter provides a brief overview of permeable reactive barrier (PRB)
technologies for groundwater remediation. We hope that it will encourage
further reading by providing a selection of references covering the now exten-
sive literature in the field of PRB groundwater remediation technologies.
1.2 Groundwater Contamination
The risks that are posed to human health and to the environment by expo-
sure to groundwater contamination are well recognized by regulatory bod-
ies, owners of potentially contaminated sites, the local community, and the
public at large. As a consequence, regulatory guidelines have been devel-
oped to both protect the environment and, where necessary, to clean a
contaminated environment to the required level based upon these guide-
line values. The remediation endpoints required by regulators, the scope
of monitoring programs, and the assignment of legal/financial liability
for remediation efforts all vary greatly from country to country (Rao et al.,
1996). Environmental literacy and public perception of the relative risks of
soil and groundwater contamination (in comparison to other hazards) can
influence regulatory policy, and the acceptable levels of contamination, as
well as the expectations of any required cleanup of contaminated sites. Such
issues play a dominant role in identifying soil and groundwater contami-
nated sites (Rao et al., 1996).
Millions of potentially contaminated sites have been identified
globally—and these require cleanup (Singh and Naidu, 2012). According
to the NRC (1994) and Rao et al. (1996), there are between 300,000 and
400,000 contaminated sites in the United States with a wide variety of toxic
chemicals identified. Total cleanup costs were estimated to be in the range
of $500 billion to $1 trillion. More recent estimates, however, show that
the number of contaminated sites could be as many as 500,000 (Table 1.1)
with many of these experiencing groundwater contamination with com-
plex mixtures of chlorinated solvents, fuels, metals, and/or radioactive
materials. Inclusion of sites contaminated in other industrialized coun-
tries with those in United States, Europe, and Australia suggests that there
are in excess of 1 million potentially contaminated sites (Table 1.1). While
there are no data available for potentially contaminated sites in develop-
ing countries from Asia, one estimate suggests the existence of millions
of such sites (Naidu, 2013) in both rural regions as well as in urban areas.
Whereas contaminated sites in the urban environment constrain urban
renewal, those present in the rural environments pose risks to the “clean
and green” image of a country in addition to posing risks to human health.
In 2005, the Canadian Environment Industry (CEI) identified more than
30,000 contaminated sites in Canada (CEI, 2005) concluding that such sites
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