Locals have been left concerned after a grout leak on a rugby pitch near where HS2 is being built.
The area on the pitch in Ruislip, in a west London borough, has been temporarily fenced-off after bubbling foam emerged last week above the ground where tunnelling is being carried out.
It is the third time the liquid has emerged from the ground after similar incidents in March and February.
HS2 says a mixture of water cement and sand - grout - was wrongly pumped to the surface through a hole that had been drilled by workers to check ground conditions.
Jatin Radia, the chair of Ruislip Rugby Club, expressed concern over the spillage.
He told the BBC: “The reality is it does cause further concerns because you’ve got local residents, local rugby club members. They’re naturally concerned about what’s going on and asking ‘is it safe’?”
It comes after a “bubbling” puddle opened up on the grounds on March 20.
Locals have expressed concern about the liquid and have even called for HS2 work to be suspended in the area.
Environmental campaigner Paul Jennings said: “Ten years go when we started on the consultation with HS2 and the Environment Agency, we were very concerned that the aquifer would be damaged by what goes on within the tunnel.
“The tunnel has a lot of fluid running around it and it’s under pressure and that’s going to find its way into cracks and holes.”
“And what has happened here is a fantastic demonstration of what our concerns were at the time. We are still worried as there is still a lot of more tunnelling to be done and we’re not sure what damage has already been done.”
Due to the problems, HS2 has switched to tunnelling fluid which it hopes is better suited to the mixed ground.
A spokesperson for HS2 Ltd said: "Our expert tunnelling team are adapting their methods to account for the variable ground conditions in this specific area. Safety is at the forefront of everything we do and they will restart continuous mining once the new approach has been assured.”
On the issue with the grout, they added: “A grout leak has taken place during our tunnelling operations. We apologise for the error. After liaison with the Rugby Club, the grout was cleaned up. The area has been temporarily fenced-off and remains safe.”
