In Situ Remediation Technologies - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 969

21.3.3 Risk Management at Contaminated Megasites

In the EU project WELCOME (http// www.EUwelcome.nl /) the management of con-
taminated soil, groundwater and surface water on large (former) industrial sites
has been addressed (Malina et al. 2002 ; Ter Meer et al. 2008). The extent of con-
tamination at these so-called Megasites is so large and complex that an integrated
cost-effective approach is required to reduce and mitigate the risks. An Integrated
Management Strategy (IMS) was developed in line with the EU water frame-
work and groundwater directives ( http//www.EUwelcome.nl/kims ). Especially, the
prevent-and-limit paragraphs of the EU groundwater directive are addressed (Ter
Meer et al. 2008). The IMS has been demonstrated by applications at four Megasite
cases, namely Bitterfeld, Germany; Rotterdam Harbour Region, the Netherlands;
Antwerp Harbour Region, Belgium; and Tarnowskie Gory, Poland. The IMS is
aimed at guiding the user through the whole process of establishing a Megasite
management plan; from the initial screening to the final definition of the remediation
scenarios and long-term site management plan. It includes:

• basic strategies of the IMS;

• a manual for technical experts and environmental managers;

• examples of the implementation of the IMS at the Welcome Megasite cases;

• an overview of the technical support tools.

The IMS-manual helps the user to distinguish the areas of the Megasite with the
highest risk and set up priorities for the level of risk reduction, degree of remedia-
tion and consequently, related investments on the basis of Risk Assessment for the
area. This process can often minimize the costs of the management and remediation
measures and maximize its effectiveness by channelling investments into the areas
of the site with the highest risk. Four basic phases are distinguished in the IMS, i.e.,
Starting the IMS, Management scenarios, Risk Assessment, Implementation.

21.3.3.1 Starting the IMS

The overall objective of this section is the provision of all criteria needed to define
a site as a Megasite, to derive the specific management tasks and objectives, and to
establish a group of stakeholders and experts. An important activity is to establish a
site conceptual model (see Fig. 21.7 for the Rotterdam harbour as an example) with
possible migration pathways defining planes of compliance to be used in further
Risk Assessment and Management.

21.3.3.2 Risk Assessment

The guideline consists of the following steps: Carry out a Megasite characterization;
Define potential risk clusters; Carry out fate and transport modelling; Determine
risks and derive local standards; Finalize risk clusters. In the Rotterdam case risks
were especially relevant for the groundwater system directly below the harbour
region, and not for the surrounding surface waters and polders. In Fig. 21.8 the area