Why are there giant yellow screws on the runway at Edinburgh Airport?

Edinburgh is one of the only airports in the UK with a stream running through it, which means water could build up on the runway during heavy rainfall.

To mitigate that and to protect the environment, the airport uses giant screws – called Archimedes screws – that have just been refurbished for the first time in 50 years, all while the airfield remained in operation.

The screws collect excess water from the runway before filtering it and pumping it back out towards the River Almond – preventing the airfield from flooding as well as protecting the environment.

For the first time in 50 years – since the main terminal was originally built – the ten-tonne screws have been refurbished.

But on an active runway with planes departing and landing every few minutes – it wasn’t an easy task.

Duncan Logan, a project manager at the airport, said: “They’ve been fully refurbished and all the electricals have been replaced with new equipment. The concrete structure itself has also had repairs made and this will all lead to cleaner water being recycled back into the burn.

“This is the first refurbishment the screws have ever had. They’ve been here for around 50 years since the terminal was first built. There were a lot of unknowns as a result, but this work should safeguard it for the next 30 or 40 years.

“The project has taken around a year to develop. Because the site is slap bang in the middle of the airfield, and we’ve got the airspace above us, there is a height restriction on the crane.

“We’ve also got two taxiways nearby, and we’ve got aircraft coming into the nearby stands. These things all make it a wee bit more complicated for us.”

As for why the screws are coloured yellow, that remains a mystery – but now they’ve been restored, they’ll be hard for passengers to miss.