Summary and conclusions, Miljøstyrelsen

Measures to remedy indoor climate nuisances

Summary and conclusions

The project is directed towards localities where a risk of unacceptable indoor climate due to contamination with volatile substances (typically tri- or tetrachloroethylene) has been identified early in the course of an investigation either near or underneath a residence or buildings of sensitive application.

The project describes, and in some cases tests a series of simple and cheap remediation measures for elimination or reduction of indoor climate nuisance due to soil and groundwater contamination. The measures described can be initiated very early in the course of an investigation so that the indoor climate nuisance can be reduced very quickly, even before a final remediation program has been prepared.

From the beginning of the project, the overall goal has been that the action taken on each site should not result in a serious increase in the cost of the total remediation project, and that the options for more extensive measures, which might be necessary after the conclusion of the contamination mapping, should not be limited.

Furthermore, it should be possible to establish the measures on the basis of limited investigations and tests. The establishment phase should be short and without significant technical difficulties. The operation phase should be characterised by a minimum of maintenance and a minimum of operational expenditure.

All goals, except one, have been realised for all the techniques described.

After a close investigation of the possible remediation solutions, it can be concluded that the financial goal of preliminary expenses less than approx. DKK 30,000 per building cannot be realised for all the remediation solutions described. The described measures cost between DKK 10,000 – 170,000. However, attention should be drawn to the fact that the range of possible solutions is so wide that it will be possible to realise goals with preliminary expenses less than DKK 30,000 when necessary.

The cheapest solutions include room ventilation in basements and measures where concrete floors are established in small basement areas (e.g. a larder or similar). The most expensive solution includes ground ventilation in vertical extraction borings or in drains under floors.

However, the remediation technique using ground extraction is very expensive, as the costs of this technique include establishment of an extraction system. Establishment of extraction system alone costs about DKK 100-150,000. However, since the extraction system can be used later at other localities, the depreciation charge will be spread over several remediations. In this way the costs per building will be significantly lower.

Three techniques are the price range DKK 50-60,000 (ventilation of the capillary breaking layer), and the remaining techniques cost approx. DKK 20-30,000.

Large reductions in indoor climate nuisance (up to 99%) can be achieved with most of the techniques described. However, some of the techniques are subject to some uncertainty. This uncertainty is due to, for example, risks in connection with establishment (e.g. bad joints in membranes) or risks in connection with basic evaluations regarding spreading. For example, if a basement floor is sealed and it later turns out that the contamination spreading through the basement walls or the other floors is more significant than expected, the effect of sealing the floor will be smaller than expected.

All the measures described can be established within a period of 1-2 weeks, and certain techniques within a few days.

The need for monitoring is fairly homogeneous for the techniques described and typically involves two measuring rounds with indoor climate measurements or measurements below floor level. Common for all the techniques described is that the extent of monitoring should be carefully considered, as this item can otherwise become financially disproportionate compared to the total cost of the measure.

All the remediation techniques are considered to be environmentally expedient, when quantity and quality as well as negative and positive environmental effects are compared. It has been evaluated that goals and criteria can be realised with limited means, without involving environmental burdens.