Contaminated Site Management - Follow up
Contaminated site investigations, monitoring and remediation can make up a substantial part of site development costs. Many factors can significantly increase these costs. One factor is technological advancements in environmental analytics, which has led to significantly lower detection limits of contaminants in environmental samples. Along with toxicological evaluations of chemicals, corresponding risk assessment procedures classify more and more pollutants at very low threshold levels as being harmful to human health and the environment. Thus, measurements can now be carried out on contaminated sites, which consider the extremely low threshold values of contaminants and in turn lead to widespread, very low-level contamination throughout many sites or even throughout whole areas and landscapes (ubiquitous background pollution).
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In the last 10 years a class of pollutants called perfluoroalkyl-substances or PFAS emerged in contaminated site management. These chemicals are per- or polyfluorinated and are therefore very (heat) stable, possess good water solubility and surfactant properties depending on the compound’s chain-length. Their environmental degradation rates are low, while transforming into shorter-chain degradation products being even more persistent in the environment. This class of pollutants is comprised of many different compounds - some estimates point towards more than 4500 substances being used for different purposes like in textiles, surface coatings, firefighting foams, and much more.
PFAS presently receive a lot of attention as contaminants having extremely low threshold levels in environmental media such as surface water, soils and groundwater. These thresholds are so low due to the specific physical-chemical properties of these chemicals, for instance having a strong tendency for bioaccumulating in the food chain (bioconcentration factors). For hazard classification their persistence, bioaccumulation and toxicity (PBT) have been assessed by EFSA (the European Food Safety Authority).
The Swiss Federal Office of Environment (FOEN) is presently reviewing the current evaluation criteria for the classification of PFAS contaminated sites (https://www.bafu.admin.ch/dam/bafu/de/dokumente/altlasten/externe-studien-berichte/expertenbericht-pfas.pdf.download.pdf/entscheidungsgrundlagen-vollzug-PFAS-belastete-standorte.pdf). The handling of exceedances of preliminarily recommended threshold values relating to EFSA recommendations is difficult to evaluate taking practical aspects into consideration. Moreover, the ubiquitous occurrence of PFAS in the form of an anthropogenic background contamination complicates the classification of contaminated sites, since according to regulation a contaminated site must be clearly defined and delimitable. It is not surprising that the present Swiss contaminated site ordnance does not define general PFAS threshold values, hence threshold values must be derived together with the authority for each individual site, where PFAS contamination has been found.
The widespread occurrence of PFAS also challenges the usual waste classification procedures, for instance during a construction project, because extremely low threshold values would lead to hazardous classifications for the excavated materials. This, in turn, would lead to special treatment requirements with exorbitant cost impacts. Looking at our industrial sites, where firefighting exercises are regularly being undertaken as required by operational permits, PFAS contamination have been or will be found over extended areas due to occurred drifts of firefighting foams during exercises in the past. The extended PFAS contamination will jeopardize development projects on such sites unless economical treatment solutions for excavated waste materials are available. Dealing with PFAS contaminated waste materials is presently a very challenging and urgent matter, where reasonable solutions must be found to balance overall benefits in a proportional manner and based on sustainability principles.
It is important to recognize that PFAS occurs widespread throughout Switzerland, as a study by the Zurich University of Applied Sciences (ZHAW) founded by FOEN and published in June 2022 has shown, "Per and Polyfluorinated Alkyl substances (PFAS) in Swiss soils" (https://www.agroscope.admin.ch/agroscope/de/home/aktuell/newsroom/2023/01-04-schweizer-boeden.html). Not surprising since extremely low detection limits achievable with today’s environmental analytics hand in hand with extremely low threshold values, PFAS contamination is expected to be widely spread also throughout very large areas. PFAS contamination should be evaluated in the context of proportionality and the risk of possible impacts on protected resources judged with common sense.