Photo: SGI

In-Place Capping of Contaminated Sediments: A Technology Overview

22 December 2016, 15:58

Polluted lake or marine sediments have been identified in at least 19 of Sweden's 21 counties. In many cases, the pollution levels are so high that clean-up measures are needed to reduce the risks posed by the pollutants. One clean-up measure (or technology) is to cover, or cap, the contaminated sediments in place with clean materials. This particular sediment clean-up technology is the subject of a new technology overview recently published by the Swedish Geotechnical Institute, SGI.

The costs for sediment clean-up in Sweden are likely to be very large and it is important that the clean-up technologies used are technically sound, cost-effective, and sustainable. Selecting the most appropriate clean-up technology, or combination of technologies, for each site requires knowledge of what types of technologies are proven-effective and available.

One technology for sediment clean-up
In-place capping of contaminated sediments is one clean-up technology that can be used. There are others, including removal (dredging) and natural recovery.

In general terms, capping involves the creation of a new sediment bottom to prevent contaminants from being exposed to and harming benthic organisms. The Swedish Geotechnical Institute, together with SAO Environmental Consulting AB, have developed a technology overview which describes the different types of capping-based remedies available, including when and where each capping technique can be used as well as the advantages and limitations of each technique.

Capping techniques and materials
Two basic capping techniques are available and internationally recognized: Isolation capping and thin-layer capping. Isolation capping generally involves physically and chemically isolating sediment contaminants from long-term exposure to organisms. In contrast, thin-layer capping generally involves significantly reducing (but not necessarily eliminating) contaminant exposure to and bioaccumulation by organisms. Different types of materials can be used in both capping techniques, including non-reactive, conventional materials (like sand) and reactive materials, like activated carbon.

Looking forward
The technology overview also includes (as separate support documents) a preliminary summary of capping projects, worldwide, as well as a general overview of internationally accepted sediment clean-up technologies in general.

It is hoped that the technology overview, plus supporting documentation, will assist consultants, decision-makers, and other stakeholders in evaluating and selecting appropriate measures for sediment clean-up at contaminated sites. It is also hoped that the publications will lead to in-place capping being seriously considered as one such appropriate technology for sediment clean-up at contaminated sites in Sweden.

Publication in several parts:

Page was updated 2016-12-22
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