Thick slurry and foam from a metro rail tunnel overflowed on to a service lane at Anna Salai on Monday evening triggering alarm and confusion among road-users.
As tunnelling work was in progress, the foam came out of a hole near a petrol bunk opposite to Spencers Plaza in Anna Salai.
According to officials of Chennai Metro Rail Limited (CMRL), the tunnel boring machine (TBM) was drilling the earth in this area and the foam came out as the soil was loose.
“The TBM has been drilling from LIC station towards AG-DMS. The foam came out of a hole near the petrol bunk. We didn’t know a hole existed there. We have already taken measures to set it right,” an official said.
Metro engineers said the slurry could have been pushed out of a borwell due to the pressure generated by the tunnelling machine 12 to 14m below the surface.
Metro rail began building tunnels to complete a four-km stretch between May Day Park and AG-DMS a week ago, more than a year after a Russian contractor abandoned work in May 2015 citing financial crunch. In June 2016, metro rail signed a contract with Afcons to complete the tunneling work on the stretch.