When the contamination of the ground and groundwater with petroleum was discovered, the ground engineering contractor NEKAB decided to use bentonite as a protective membrane.
The discovery of the petroleum contamination happened during the ground preparation works for the construction of commercial property in Luleå, Sweden.
Old storm sewers
“We uncovered old storm sewers full of petroleum contaminations which had leached into the ground and groundwater. Of course, we decontaminated the ground. But because the groundwater was also contaminated it would still affect the water pipes we were due to place for the incoming water” says Daniel Johansson work manager at NEKAB.
Even though the contamination levels after sanitation were below allowed health and safety limits, it was still considered likely that the petroleum would penetrate the plastic pipes and flavour the drinking water if they did not take protective measures.
Finely ground bentonite
Daniel had previously used bentonite mats but knew from experience these would become difficult to manage when soaked in the deep trenches. It was therefore suggested to use finely ground bentonite in the 60 metres long and 2.5-metre deep trench. In total, NEKAB placed 30 tonnes of bentonite around the pipes. LKAB Minerals delivered this bentonite from the production facility at the nearby plant of Sandön in Luleå.
“The bentonite forms a barrier which, on contact with water, forms a clay and therefore effectively prevents the water from passing through to the water pipes; a solution that worked well for us and that we were therefore allowed to use” Daniel explains.
Bo Öhman, Sales Manager at LKAB Minerals in Luleå adds ”Thanks to our service-minded production facility close to the project we could expedite the order the day after we received it and deliver directly to the site for placement. LKAB produce and use large quantities of bentonite for our production of iron ore pellets, but we also sell it on the industrial minerals market in several countries.”