Miljøprojekt, 1117; Teknologiudviklingsprogrammet for jord- og grundvandsforurening – Metoder og økonomi til fjernelse af restforurening af benzin - Nykøbingvej 295, Radsted

Metoder og økonomi til fjernelse af restforurening af benzin

Summary and conclusions

At an abandoned fuel station at Nykøbingvej 295, Sakskøbing, a significant soil and groundwater contamination with gasoline was found in 1996. Upon removal of two underground storage tanks and part of the contaminated soil the remaining contamination was left in the ground, adding up to some 600 kg of gasoline.

This report aims at evaluating which type of remedial action is suitable for the mentioned type of contamination, including which is suitable on the actual site given the specific geological setting. 10 years of natural attenuation has not been sufficient to remove the risk of contamination for the groundwater downstream the site. Therefore it has been relevant to assess which remediation methods would be applicable in 2006 in order to remove the remaining contamination, and to compare the costs of such an action in 2006 with costs of remedial action in 1996.

The assessment is made on basis of 4 possible strategies for remediation:

a) an immediate and full clean-up, typically by excavation, B) initiation of a long-duration remedial action C) partial clean-up followed by monitoring, and finally D) a delayed remedial action, when option C is deemed insufficient after some years.

It is concluded that remediation by big-diameter drilling or excavation implying use of sheet piling would be the most appropriate method in 1996, and that it would have been cost-beneficial either to carry out a complete remediation immediately or to initiate a two-year remedial action by multi phase extraction as a supplement to a partial excavation. The best option in 2006 seems to be removal of contamination by big-diameter drilling in the unsaturated zone and in the upper part of the saturated zone, combined with airsparging in the contaminant plume.