The methods
The methods to carry out the works are dictated by the circumstances. Thames Water and J Murphy & Son look to keep water supplies going during the duration of the works but the configuration of the existing pipe network in each site dictates which method can be used to replace/upgrade the pipes and therefore whether that is possible.
Please find below a brief description of the methods of replacing/upgrading the existing local water distribution network:
➢ Open Cut Trenching:
This involves a progressive site set up. A trench excavation (D-1.2m, W-0.8m, L 50-80m) is carried out for the installation of the new pipe. Associated trench excavations for customer supply pipes and fire hydrants are also undertaken and incorporated with the site area. Parking and road closures are usually to facilitate the safe and expedient undertaking of these works. This method occurs when the design requirement dictates a significant increase in the diameter of the new pipe and / or where Insertion or Pipe Bursting is deemed unsuitable.
➢ Insertion:
This involves a more static site set up. Excavations are carried out at key locations on the existing water mains for launch and reception pits and for customer service connection points. Associated excavations for customer supply pipes and fire hydrants are also undertaken which may sometimes involve a separate site adjacent to the main site. Preparation works usually takes up to four days but this depends on the amount of excavations and supply pipes. The existing water pipe is then shut down, sections are cut out, and a new smaller diameter pipe is pulled through. All supplies are then transferred on to the newly reconnected pipe. Parking and road closures are usually to facilitate the safe and expedient undertaking of these works.
➢ Pipe Bursting:
This process is similar to that of Insertion except that the existing pipe is expanded to host the new pipe of similar (or slightly larger) diameter.