Construction of a new 6.5km pipeline began in summer 2019 and is planned to finish by spring 2023. It will connect Bristol’s existing trunk sewer in Lawrence Weston to the Frome Valley relief sewer near Cribbs Causeway and will direct waste more efficiently around North Bristol to our water recycling centre in Avonmouth.
The majority of the sewer has been constructed by tunnelling underground using a tunnel boring machine (TBM), reducing the need to dig trenches. Tunnelling will take place underneath key landmarks, including the M5 motorway and Network Rail’s Henbury Loop freight railway.
The Vertform manhole shuttering system is being successfully used on the North Bristol Relief Sewer Project in 2020. There were 6 large diameter manholes to be constructed on a DN1800 and DN1200 sewer. In addition there are a further 6 small diameter manholes to be constructed on a DN450 and DN600 sewer. The Vertform system offers a big advantage over traditional methods in the construction of manhole chambers. The system consists of a range of fibre glass panels which can be arranged to form a channel without the need to bench the manhole afterwards. The manhole base is constructed in one continuous concrete pour. The system caters for a range of pipe diameters from 300mm up to 1800mm. In addition various panels are provided which can accommodate a range of inlet and outlet pipe angles.
The Wessex Water region is a stronghold for ‘great crested newts’ and therefore of particular concern during the sewer’s construction. An amazing and innovative solution has been introduced into locating these protected creatures - ‘Freya’ the ‘Newt Detection Dog’. Wessex Water are the first utility company in the UK to have an in-house great crested newt detection dog, owned and trained by ecologist Nikki Glover.
If construction works are within 250 metres of breeding ponds and we are likely to cause an offence under the legislation, we must apply for a licence from Natural England. We would then be required to fence off the construction area and carry out pitfall trapping (buckets sunk into the ground), which could take around 30 days to complete.
Nikki and Freya will be working alongside the team from Murphy during the construction of the new sewer as an additional tool alongside current mitigation measures.