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"Introduction"
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Introduction

Fractured low permeable sediments / soils cover a major part of the surface, especially in Northern and Central Europe. These rock types possess a special problem in relation to spreading of contaminants into groundwater aquifers, since the fractures form hydraulic avenues through the otherwise low permeable clayey sediments/soils. Traditional remediation technologies used in high permeable soils (extraction, ventilation, etc.) are primarily based on vertical wells that are installed on the subsurface. Regarding the fractured low permeable sediments, the problem is that the transport takes place predominantly in the vertical fractures, and in the normal vertical wells, NAPL seem to bypass most of these fractures. Therefore, any remediation method based on such wells is expected to be inefficient.

In order to perform effective in situ remediation of fractured sediments, a large number of fractures have to be connected to a well or to a highly permeable sediment layer. The bulk hydraulic conductivity in the fractured sediments may be stimulated either by increasing the fracture aperture and/or the connectivity between fractures and/or the density of the fractures. During hydraulic fracturing, new fractures are introduced into the system, and aperture of the existing fractures is increased due to the uplift of the soil above the fracture.

The STRESOIL project (IN SITU STIMULATION AND REMEDIATION OF CONTAMINATED FRACTURED SOILS), Contract Number 004017, is carried out within the Sixth Framework Programme of the European Community. The “fractured soil” stipulated in the project title is glacial till - one of the most common geological sediments in the EU countries. The low permeable, fractured till - while contaminated - represents a great challenge for environmental cleanup procedures. Particularly, if the contamination is present in the unsaturated zone removal of the pollutant becomes very difficult.

A combination of field experiments involving various approaches, laboratory investigations of rock and water samples as well as computer simulations will be employed to solve the problem. A combined effort of a team consisting of experts from Greece, France, Poland, Denmark and USA should within a three year period result in selection of a suitable method for cleanup of the Kluczewo location in NW Poland – the site selected by STRESOIL for field experiments. It is expected, that the findings of the project will have significant practical applicability in several Community countries.