Guernsey States have spent £8m on a court battle with a company that produces a fire-fighting foam used at Guernsey and Alderney airports.
The long-running claim against 3M ended in the High Court in the UK this week, with an early settlement.
Under the terms they have to pay £1.4m for the legal costs of 3M and £6.6m for their own.
The hearing took place after traces of the chemical PFOS, normally found in fire-fighting foam supplied by the company, was found in water in the islands.
The judge found in favour of company 3M.
The States were seeking £27m, to cover expenditure the island has already spent, totaling £10m, and costs for the next 20 years.
Both sides have now dismissed any claim against each other.