Lincoln's St Marks Shopping Centre is marking 15 years since it was opened. In the second in a series of features, Ed Grover finds out how the discovery of an underground oil spill required an ingenious solution to keep the project alive...

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The St Marks development was thrown into doubt when thousands of gallons of diesel were found under the current Debenhams site.

Investment from landowners Barclays Bank Staff Pension Fund would only be assured if a way to remove the fluid was found.

Development director Giles Walter, who oversaw the St Marks project for construction firm Simons, explained the desperate measures required to deal with the slick.

"After completing the first phase of the development we had to decide what to do with the other part of the site, because it was a big chunk of land with a redundant railway station sitting on it," said Mr Walter.

"At that time, what wasn't part of the scheme or ownership of Barclays was the offices of Lincolnshire Road Car, a countywide bus and coach company, on St Mark's Street.

"We concluded that we had to buy that building to give us enough space for a Debenhams department store, which is obviously what we see now.

"Lincolnshire Road Car were quite happy to move because it really had got too big for them.

"So we started the negotiations and we decided, quite rightly, as part of the due diligence to test for any contamination.

"We used a sister company called Delta-Simons, and one day I got a call saying 'Giles, you had better come down and take a look'.

"I remember arriving on site and they had dug this huge great hole.

"And at the bottom you could see this ground water, because it was not far from the river.

"It was very scientific but for the purposes of what they wanted to show me, they dunked a jam jar into the water and pulled it up, and inside was water with neat diesel on top.

"We then started to investigate, because obviously we didn't want something like that there.

"It transpired there had been some tanks underneath the Road Car building, one of them had ruptured and there had been a serious leak.

"I think it had actually spilt in the 1970s and it was still sitting there on top of the ground water.

"I think they reckoned there might have been up to around 50,000 gallons of diesel.

"I don't know if that was right or wrong, but that was what was going round.

"Obviously it had to be dealt with, because you couldn't start putting buildings up with neat diesel underneath, especially as it was quite close to the river.

"So to deal with it what we ended up doing was, underneath Debenhams, to dig an enormous trench.

"We then put a whole series of wells at the bottom of this trench, which we filled with gravel.

"The idea was that we sucked out ground water and diesel into a pump room behind where the ATMs are now.

"And of course nobody will know this, but for about two or three years after Debenhams was built we were still sucking out diesel.

"And every so often a tanker used to come to collect the diesel that we had collected.

"It was quite challenging engineering actually.

"I think the diesel was reused, but I'm not sure what for.

"And that's the sort of thing people would not have a clue about.

"From a financial point of view, Barclay's Bank Staff Pension Fund didn't want to be owning a site that was full of diesel.

"And so we had to resolve that and come up with a solution that would ultimately create a clean site, because if it wasn't taken away it would still be there now.

"The worry was that if there had been a breach in the river wall, the diesel could have got into the Brayford and who knows where.

"The danger with contamination like that is that it could end up in water courses."

The first phase of the development, including Toys R Us, was completed in 1993.

As reported in last week's Echo, after other subterranean finds were unearthed, including the remains of 20 monks, Debenhams opened in time for Christmas trading in 1996.