Firefighters prevented a pollution disaster after working around the clock for seven days to pump more than 60 million litres of contaminated water from a disused Cornish mine.
Had the filthy water escaped it could have damaged the Carnon River and the Fal Estuary.
Teams of four firefighters took turns operating two high volume pumps at the former Wheal Jane mine near Baldhu and Chacewater in west Cornwall.
Crews sunk the pumps 58 metres (190ft) down two separate mine shafts.
Cornwall is the first fire and rescue service in the country to successfully use a high volume pump at this depth.
Lance Kennedy, Cornwall Council's portfolio holder for community safety, public protection and waste management, said: "Our fire service has again demonstrated its ability to lead in new ways of protecting the environment and community.
"The high volume pump has proved to be an excellent addition to our equipment during floods, fires and now environmental protection."
The mine closed in 1991 when mining activity stopped.
Following an incident in 1992 when contaminated water from the flooded mine spilled into the Carnon and the Fal a specialist plant was set up by the Environment Agency to treat the mine water before discharging it into the estuary.
The plant is now operated by Veolia Water Solutions and Technologies on behalf of the Coal Authority.
Defra funds the Wheal Jane operations.
Cornwall's chief fire officer Des Tidbury said the exercise had proved how well Cornish firefighters work.
He said: "The Wheal Jane incident has proved to be a very demanding exercise over a prolonged period of time.
"As usual our firefighters have proved, yet again, that they can deal with anything that is thrown at them."