Mt Albert Sludge Pipeline Repair

Rebuilding the tunnel of sludge

PROJECT: Mt Albert Sludge Pipeline Repair CONTRACTOR: Brian Perry Civil (BPC) CLIENT: Wellington Water VALUE: $8m

When two critical sludge pipes collapsed deep in a Wellington tunnel in January 2020, BPC delivered a world-leading solution during the Covid-19 lockdown.

The collapse meant trucks had to transport sludge 24/7 around the capital’s south coast at a weekly cost to ratepayers of $600,000.

Wellington Water engaged BPC and Stantec to design a solution and carry out repairs as soon as possible. The challenges were huge. Both ruptured pipes were encased in a concrete surround and the tunnel had only one access shaft.

Wellington Water agreed with the project team that a full pipeline liner was the best repair method. Two 1.8-kilometre liners were procured from Amex Samivar in Germany. To prepare for their installation BPC carried out the new pipe diversion works during the tight one-hour pump station shutdowns, working seven days a week in very challenging conditions.

On May 21 the first pipeline was switched back on, putting a halt to the 24/7 trucking operation, with the second pipeline repaired in June. BPC then designed and installed an overpumping system that removed the need for repetitive shutdowns and allowed safe access to the work.