A TOXIC lagoon that has troubled nearby residents for years will cost a staggering £40 million to clean up.

And if the clean-up operation for the lagoon in Rhos is given the go-ahead, it could take about four years to complete.

It has been estimated the former brick clay quarry at Llwyneinion contains 94,000 tonnes of liquid tar, a by-product of oil refining, dumped there before 1972.

The poisonous depths of the lagoon had never been fully explored until last year when a scientific investigation was carried out by environmental engineering specialists from Germany.

As part of a joint project with Environment Agency Wales, grant aided by the Welsh Assembly Government, the four scientists from Baufeld Engineering took to the water aboard a special raft in a bid to uncover what lies below the surface.

They took 73 samples of acid tar and lagoon water, which revealed a high concentration of pollution hydrocarbons, poly-aromatic hydrocarbons and sulphur.

A council spokesman described the materials found as ‘unpleasant’ but added: “It remains contained and is secure and safe from the public.”

In a report to be considered by the council’s environment and regeneration scrutiny committee on Wednesday, strategic and performance director Philip Walton says Baufeld estimates the clear-up costs for the site at about £40 million.

He adds that the company also reckons it would take about four years to clean up the site, based on removing 120-150 tonnes of material a day.

However, Mr Walton points out that in some European countries – although not in the UK – acid tar such as that found at Llwyneinion has been used as a secondary fuel.

He says the £40 million estimate is based on exporting the acid tar to Germany to be used as fuel but that if a UK outlet could be found the costs could be “reduced significantly”.

The council is now holding further talks with Baufeld, Environment Agency Wales and the Assembly Government to discuss ideas for taking the clean-up forward, including a review of funding options.

The council spokesman said: “Funding for the work has not yet been identified.

However, if it was agreed in the future that clear-up of the site was to go ahead the council would look to outside partners and agencies for funding.”

Ponciau councillor Paul Pemberton, in whose ward the lagoon lies, has been campaigning for a proper clean-up of the lagoon for the past 10 years.

He has pledged to call a meeting for local residents to fully update them on the findings of the investigation.