Characterisation and monitoring of in-situ remediation of chlorinated hydrocarbon contamination using an interdisciplinary approach

To meet future challenges in urban development, more housing via densification of cities take place for sustainable urban planning. This is done by expanding housing into often contaminated industrial sites. Growing concerns are the 2000 sites in Sweden contaminated with carcinogenic chlorinated hydrocarbons (dry-cleaners and industrial solvents). The main remediation technique in Sweden is the costly and micro-ecologically damaging excavation and landfilling, i.e. moving the pollutants from one site to another. This strategy leads to large transports and the exposure of dangerous compounds. SEPA recommends the use of in-situ methods. Increased use of in-situ remediation will lead to large savings for clean-up, and contribute to EU Water Directive requirements and to reaching our national environmental objectives. In this project, we propose an integrated monitoring with geophysical and biogeochemical, methodologies to better understand and follow in-situ remediation processes. Continuous geophysical observations during the remediation will together with biogeochemical sampling and analyses help follow the development underground. Today, the monitoring of the remediation action and confirmation on a “good enough” is very uncertain, due to the current investigation techniques with point source monitoring. With our combined approach, we can retrieve a comprehensive coverage of changes underground, reduce uncertainties and costs for monitoring the in-situ remediation.

To meet future challenges in urban development in general, and in particular the need of more housing, densification of cities are a major issue in future sustainable urban planning. Densification of cities through are often met by expanding housing into old industrial sites and changing them into attractive residential areas.

Sweden has 82 000 contaminated areas. Increasing funds are allocated for remediation but at the current pace the national environmental quality objective “A Non-Toxic Environment” will not be reached as envisioned by 2020.
A growing concern is sites contaminated with chlorinated hydrocarbons, in Sweden approximately 2000 sites have been registered. Most of these sites are previous or current dry-cleaning facilities or industries using chlorinated hydrocarbons as solvents. In this project we will focus on sites where soil, bedrock and groundwater are contaminated with chlorinated hydrocarbons such as tetrachloroethene (PCE) and trichloroethene (TCE). These compounds are highly carcinogenic.

The main remediation technique today in Sweden is excavation and landfilling of contaminated soil at designated landfills, i.e. moving the pollutants from one site to another. This strategy has been criticised since it leads to new environmental concerns, such as large need for transports and the exposure of dangerous compounds to humans and the environment. Moreover, the excavation and/or physical treatments are costly and micro-ecologically damaging to the local environment. Therefore the recommendation issued by the Swedish Environmental Protection Agency is to increase the use of alternative methods by 2020, versus the current “dig and treat”. Increased use of in-situ remediation would lead to large savings considering the billions of SEK being spent for clean-up, and contribute to Sweden meeting the EU Water Directive requirements and our national environmental objectives “A Non-Toxic Environment” and “Good Quality Groundwater”.

The proposed project aim at improve the understanding of the conditions for in-situ remediation of chlorinated hydrocarbon contaminated sites, e.g. where dry cleaning facilities and mechanical industries have been/are active. Contamination by chlorinated hydrocarbons is associated with severe risks to human health and the environment and is therefore a major problem around the world. There is therefore an urgent need for efficient methods for monitoring of remediation actions at these sites. The proposed project address the challenges associated with the monitoring and follow up of in-situ remediation of chlorinated hydrocarbons and our team represents the academia, private industry, and responsible authorities and we form an effective base for implementation of new research into different sections of the society.

The development of in-situ remediation methods have been delayed due to doubts concerning the effects on the remediation techniques. However, over the last years increasing evidences in the recent scientific literature prove the effectiveness of several in-situ remediation approaches. Furthermore, many sites are only possible to remediate in-situ, due to the characteristic of the contaminants, the local geology and hydrogeology and the urban character of the site. Therefore, there is a strong need for an exhaustive interdisciplinary procedure for monitoring and verifying the remediation processes due to the in-situ character.

In this project, we propose an integrated monitoring with geophysical, geochemical, biological, and isotopic methodologies to better understand and follow the man-induced processes taking place when remediating at the site. Continuous geophysical observations during the remediation action will together with biogeochemical sampling sampling and analyses help follow the development underground, i.e. the degradation, contaminant movements within the soil and groundwater or by gas diffusion.

Today, the monitoring of the remediation action and a confirmation on a “good enough” clean-up is costly and very uncertain, due to the current investigation techniques with point source monitoring (i.e. groundwater sampling in wells) in larger or smaller time intervals. With our new combined approach, we can retrieve a comprehensive coverage of the changes underground and at the same time reduce uncertainties and costs for monitoring and follow-up of the remediation actions in-situ.