Groundwater-Related Risk Assessment - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 775

17.5 Risk Management

17.5.1 Scope

In the Introduction chapter (Section 1.6.1) Risk Management was defined as the
design and application of strategies for dealing with risks. Risk Management is
appropriate when the conclusion from a Risk Assessment is that a particular risk
is unacceptable. It includes avoiding the risks, mitigating or removing risks and, last
but not least, communication about the risks with the parties involved. It was con-
cluded in this section that the keyword in Risk Management is risk reduction . Other
conclusions from this section, which also apply to contaminated groundwater, are:

• ways to achieve risk reduction are source control treatment, or blocking the

pathway from source to receptor;

• the challenge is to find the optimum balance between the most effective and most

cost-efficient way of doing this by weighing the short-term advantages and the
costs of aftercare.

It also was stated in the Introduction chapter that remediation, that is, in its most
strict definition elimination of the source and the resultant groundwater contami-
nation, is the most direct way of risk reduction. However, remediation often is too
drastic an activity, whose results are not in alliance with the social and technical
impact at the site and the costs.
Risk Management approaches for contaminated groundwater are still evolv-
ing. In the late 1970s, Risk Management was often the same thing as complete
removal of the contaminants and, hence, of the risks involved. Pump-and-Treat
was the most popular mechanism to achieve this goal for groundwater contami-
nation. Since groundwater is difficult to assess, however, groundwater remediation
is relatively expensive. Moreover, given the complex exchange of contaminants in
the groundwater and the solid phase of the aquifer, the course and time lapse of
Pump-and-Treat remediations are difficult to predict.
Today, many creative solutions for the Risk Management of groundwater are
applied. Nevertheless, the prevention of groundwater contamination (aka: prevent
and limit approach ) is by far the most cost-efficient approach with regard to the
maintenance of a sustainable groundwater quality.

17.5.2 Natural Attenuation

Modern groundwater Risk Management is nearly inconceivable without the clean-
ing qualities of the organisms. Since the mid 1990s Natural Attenuation , that
is, degradation and dilution of contaminants in the groundwater, evolved into
an extremely important instrument in groundwater Risk Management. Natural
Attenuation procedures are often combined with Pump-and-Treat technologies,
nowadays for a detailed exposition on Natural Attenuation, see Chapter 22 by Peter
et al., this topic.