Authors:
Sandra Roost | Orbicon A/S | Denmark
MSc. Jens Aabling | Danish Environmental Protection Agency | Denmark
PhD Nina Tuxen | Capital Region of Denmark | Denmark
Head of section Trine Korsgaard | Region of Southern Denmark | Denmark
Helle Overgaard | The Capital Region of Denmark | Denmark
This is a proposal for a session on how the EU Water Framework Directive is handled in Europe with focus on contaminated sites threatening surface waters. In addition to the following abstract, we suggest two proposals more for oral presentation at the session.
• Experience with the Water Framework Directive and contaminated sites in the Netherlands by Eric Verbruggen (RIVM, Netherlands)
• Challenges and experience for the Danish authorities in screening and identifying contaminated sites threatening surface waters in Denmark by a representative from the Danish regions.
If this proposal for a session has your interests, we will submit abstracts on the two proposals. If you do not find space in the program for this session, we hope that the following abstract may be admitted as a lecture.
Abstract: Identification of contaminated sites threatening surface waters
Background
The implementation of the EU Water Framework Directive requires an integrating and holistic approach to legislation for water bodies with a goal of obtaining good environmental status for all receiving waters. While the risk from contaminated sites to groundwater has received a great deal of attention in the past, the risk from contaminated sites to surface waters (streams, lakes and coastal waters) has not yet been well examined. In Denmark alone there are more than 30,000 contaminated sites are registered – many of them located close to surface waters. However, the hypothesis is that only a minor part of these actually pose a real risk towards surface waters. Thus a robust method is needed to identify the few relevant sites which still comply with the precautionary principle.
Activities
Together with leading experts from universities, consulting companies and regional authorities (who are responsible for handling contaminated sites in Denmark) the Danish EPA developed a screening tool to identify contaminated sites that threaten surface waters. The screening system integrates national data of the contaminated sites: location, distance to surface waters, contamination activity, contaminant area and mass flux and calculates the mixing in surface waters. The environmental effect in surface waters was done by comparing the calculated concentrations with maximum allowed concentrations within designated mixing zones. Since the data availability and quality differs for the contaminated sites and surface waters, the screening is based on conservative default values that can be obtained from existing databases followed by a site specific assessment in order to improve the screening evaluation.
A sensitivity analysis on the input parameters for the screening tool is currently being done, aiming at focusing the effort used in obtaining the most important input parameters. Also, a description of site specific assessment activities has been done, including archive search, site inspection and simple field investigations.
Results
Assessment of the more than 1500 different possible contaminants revealed that 150 were relevant with respect to risk to surface waters. The 150 contaminants were divided in 16 classes each represented by a “worst case” model compound. Of the 30,000 registered contaminated sites, 15,000 are registered due to known activities that may involve handling of critical contaminants, but no field investigations have been carried out to confirm the presence of contaminants. Thus all activities were allocated model compounds. The maximum travel length of a contaminant plume for the model compounds were determined based on literature review and expert interviews so compound specific distance criteria could be determined. Also, conservative estimates of contaminant mass fluxes for activities and model compounds were made. Mixing in streams were calculated using analytical models that were developed (a simple and a more advanced) and mixing in lakes, fjords and along the coastline was calculated by specific numerical modeling using MIKE models. All input data are controlled by databases and GIS and implemented in a webtool.
The screening process has resulted in approximately 2500 sites that are divided between the 5 Danish regions for individual assessment which is expected to result in a list of 200-500 sites where further investigations/remedial actions are required. The most frequently found contaminants are chlorinated solvents and the most frequently affected surface water type is streams.
The sensitivity analysis has revealed that good knowledge of the geographical, geological and hydrogeological conditions are important – for instance the flow direction and the likelihood of hydraulic contact between groundwater and surface water. In addition, the type of contaminants and type of point source is crucial information to ensure a reliable risk assessment. Finally, simple inspection of the surface water contribute to the subsequent risk assessment.