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Innovative gravity sewer transformation

Our team in Preston recently transformed a damaged pipe bridge into a new gravity sewer!

An existing pipe bridge had suffered damage at Fishwick Bottoms in Preston due to the support pillar being washed away. Our team ensured the site was safely set-up with barriers before conducting a survey, removing existing rail systems, fences, and shrubbery.

The twin wall pipe work was laid in the watercourse allowing the backfilling and laying of the gravity sewer. Further trial holes were excavated by SUS staff as advised by a United Utilities engineer as well as installing rock bags to prevent erosion. Our engineer then constructed 2100mm diameter manholes, 2 metres deep and a Veter stopper was set up to facilitate diverting flows, which were later transferred via overland pipework.

Finally, our team installed 15m of ductile pipework fittings and diverted from and to the existing sewer forming the new gravity sewer. The new pipework was connected upstream and downstream and patch liner was installed, and we removed the existing pipework, disposing of it safely.

The new gravity sewer is much safer than the old pipe bridge with less risk of becoming a liability if pollution occurs in the area. It also requires much less maintenance and does not have to be inspected as frequently as the old solution, making the gravity sewer a long-term saving for our client United Utilities.

After the new system was installed, tested and more shrubs were removed, our team replaced the pedestrian rail system as well as fitting a new motorbike restriction barrier in partnership with Preston County Council to make the area safer for pedestrians. We also installed a new litter bin and reinstated the road, overall making the area cleaner and safer for the community.

Alf Gregory, Civils Compliance Manager at Sapphire Utility Solutions said “The whole team performed extremely well considering the frequent change in scope of work. The project did exceed the original planned duration by a short amount of time however the job was completed to the highest standard possible. Well done team!”

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