Reality is always changing: Developing and implementing the megasite monitoring program
Introduction
The monitoring of megasites is legally required by the Water Framework Directive (WFD) for controlling and analysing of the chemical conditions and the trends in diffusion of contamination, thereby providing for the protection of the water receptors. The performance of remediation measures is assessed in the remediation attendant monitoring, which is planned separately in the scope of the implemented measures.
Due to the environmental risks at megasites, monitoring cannot be seen as a management strategy itself. Monitoring is meant to measure the performance of the selected risk based management scenario (and all associated measures) over long timeframes. In many cases Monitored Natural Attenuation is part of the scenario (i.e. applied at low contamination areas in the RMZ and at a later stage in the remediation process for the reduction of residual contamination). In addition to MNA, many measures need to be taken and each technique or technology used has its own monitoring requirements to measure its performance. The special challenge for megasite management is how to cost-effectively monitor all measures included in the secenario.
Cost-effective monitoring needs to be integrated into the management of megasites at an early stage. The use of control planes (planes of compliance), as earlier established in the megasite conceptual model building, can be helpful in setting up the monitoring plan. Cost-efficiency is achieved by a continuous adjustment of the monitoring concept on the basis of an assessment of each sampling campaign by means of a numeric model. After the performance of risk reduction measures or introduction of restrictions of use, the monitoring provides for the control of the long-term compliance with defined quantitative and qualitative local threshold values. The complete decontamination of a megasite is technically and/or financially not feasible, thus for the protection of receptors a megasite monitoring is initially unlimited with respect to timeframe.
The procedure for developing and implementing a monitoring program at a megasite is structured in the following manner:
- Basics for developing a monitoring program for megasites
- Conceptual model and implementation
- Interpretation and assessment of data and adjustment of the monitoring program
- Quality assurance and control
In addition to the monitoring of megasites, a procedure for Monitored Natural Attenuation (MNA) needs to be developed.
Output
The output of this step is the comprehensive monitoring program for megasites aiming at the surveillance of the groundwater conditions, and corresponding with the planes of compliance in accordance with the EU-WFD, as well as the control of the sustainable performance and success of implemented risk reduction measures.
