David Plumb keeps pollution out

When decontaminating the land at a service station, you would expect any contamination to be petrol, diesel or oil that had originated from the site’s own tanks. In that case cleaning the land is a relatively straightforward procedure of removing all the contaminated material to an approved landfill site and filling the hole with clean material – but what do you do when the contamination is leaching in from outside the site?

That was the challenge that faced fuel site specialist David Plumb & Co, when it discovered the presence of Pentachlorophenol (PCP) on a former Esso site in Kettering that the company was decommissioning. The land is to be redeveloped for housing.

During the process of demolishing the site’s superstructure and excavating its tanks, the company’s environmental consultants take a number of core samples to test for contamination. In this case, the consultants did not find the fuel residue that might have been expected, but PCP – an unpleasant chemical that is normally used for preserving wood.

The likely source was on the other side of an adjacent road, on a patch of wasteland that had formerly been used as a wood yard.

Says David Plumb director, Nigel Plumb: “The old wood yard had closed years before the Esso station had even been built and the contamination was still leaching under the road and into our site, so the contamination must have been considerable.

“With our experience and specialist equipment, removing and dealing with the contamination from the site itself is straightforward enough, but it became obvious that any clean material we used as backfill would also have become contaminated fairly quickly.”

The solution was to build what amounts to an underground barrier.

The four-week process began with a partial excavation to identify the exact extent of the contamination and to insert a row of 80 x 4m deep KDX trench plates at the edge of the site, to hold back the earth under the road. Once these were safely in place, the 1,800 tonnes of earth from, and immediately around, the contaminated area could be removed by covered vehicle and taken to an approved landfill site.

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