Wessex Water has said that work on the £15M Frome Valley relief sewer scheme has reached the final phase with completion of a tunnel below the M4 motorway.
The tunnel at Three Brooks Local Nature Reserve in Bradley Stoke is a key part of the 5km long diversion sewer that will take flows from South Gloucestershire to Bristol sewage treatment works in Avonmouth.
The tunnel boring machine used to drive the 1.8m diameter tunnel below the motorway was launched in August last year.
“The tunnelling under the M4 has been successful and we are in the process of completing manhole and sewer connections in the area,” said Wessex Water project manager Mike Bryant.
“Work in the local nature reserve will be complete and the site will be reinstated by the end of March 2018.
“We’ve excavated up to 3.1km and crossed numerous features such as the River Frome, although the sewer is predominantly being constructed across fields and has had minimal impact on the public.”