Environmental Engineering Reference
In-Depth Information
Some consider MNA as a panacea, a magic solution to contamination prob-
lems. Detractors, however, will argue that this is only the case over significant
timescales. Nevertheless, Natural Attenuation processes reduce the impact of past,
present and future soil and groundwater contamination. Contrary to perceived
wisdom, in some instances Natural Attenuation can be fast, for example in the
case of a limited impact of readily biodegradable contaminants. In a specific
recorded instance of a new spill, management of the contamination through MNA
occurred faster than the administrative timeframe for the management of the
contamination.
Obviously, when MNA eliminates the contamination to such extent that the risk
to humans and the environment are acceptable there is no reason for further action.
For instance, if contamination is limited to an operating industrial site and the risk
of exposure of the workers is acceptable, it is not more efficient to invest in pre-
vention measures then in remediation. Remediation would not improve the safety
of workers, in fact it could even supply a (temporary) exposure pathway. On the
other hand, investment in prevention measures will reduce the risk of occurrence
of new incidents and their impact on the subsoil, improving the workers' safety
and increasing the level of environmental protection, while MNA will address any
historical contamination.
24.7 Managing Megasites; An Integrated Approach
In broad terms, megasites can be described as large conurbations of sites where
contamination has arisen independently, but in which contamination is so wide-
spread that the problem extends across the whole area rather than individual sites.
Such sites can cover large areas, but they could also be smaller areas where several
sites with different operators and owners are linked by overlapping and/or shared
land and water contamination problems. As contamination develops and spreads, the
environmental problems caused by these individual sites become inter-linked. The
management of such megasites may therefore be facilitated by taking an overarching
approach, rather than trying to deal with each site on an individual basis. This is
especially true for groundwater, as contaminants are not limited to individual site
boundaries. But even where contamination problems in the subsoil remain relatively
discrete there may be economic, social or environmental advantages in taking an
integrated approach.
The management of megasites poses major challenges to the current paradigm
of contaminated land management, for example by advocating a multi-site owner
response. . Such an approach should be supported by soil and (ground)water pol-
icy and legislation, with a recognition of risk-based decision making specific to
megasites. The case study of the
Port of Rotterdam industrial area
provides a good
example of an integrated megasite approach, where a large number of interests carry
out operations on a number of sites. The area around the Port of Rotterdam covers
approximately 3,000 industrial sites. Thousands of contaminant sources are thought
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