Making the final cut: Redoubt Road night works go off without a hitch

A major feat of planning, cooperation, timing and construction was pulled off at the Redoubt Road reservoir complex on Friday night – while most of Auckland slept.

The work, which was three months in the planning, involved cutting into the Waikato watermain to connect the newest reservoir's pipework.

Project manager Martin Hughes says this was the last of four connections required for the project.

"This one needed the most input from the operations team because we had to shut down the Waikato Water Treatment Plant and Waikato watermain."

The complex's third reservoir went into service in March but was only receiving water from the Ardmore Water Treatment Plant.

This final cut-in means it now gets water from both Ardmore and Waikato.

Lifting out the existing pipe in the rain.

Finding the right window of time for the work was challenging – Auckland's total water demand had to fall below 420 million litres per day before the Waikato plant could be shut down.

Head of service delivery Sharon Danks says there were two previous attempts to put the plan in motion, but demand remained too high to risk taking the Waikato supply out of the network.

"Removing 225MLD of production capacity from the network has a really significant impact. The weather was on our side this time – rain lowers demand because people aren't out washing their cars or watering the garden."

Luckily it was just the right amount of rain – too much would have potentially caused issues.

"We manned all the treatment plants because there was a risk that the rain coming through would be more than expected. For Huia, it doesn't take much rain to increase the turbidity of the water and the plant would need to be manned to facilitate flow changes.

"For Ardmore, there was a risk of 60-80mm of rain which could have meant changing the treatment processes and the dams which the water was drawn from. Luckily, the weather went off to the east and didn't hit Auckland at all."

Sharon says operations engineer Lucas Gan planned and coordinated the operation and worked with the treatment plant staff to make sure everything was in place for the night works.

"The main risk was to the treatment plants and Lucas did a great job of planning and coordinating the shutdown."

Installing the new pipe.

Martin says the work went smoothly with no interruption to supply and was finished ahead of schedule.

"The Waikato plant was turned off at 11am on Friday and the transmission operations team isolated the pipe and drained it down.

"The pipe was handed over to the cut-in team at 6pm. The first cut into the existing pipe started at 8pm and the new pipe was in place around 10pm. The bulk of the welding was finished by 5am on Saturday and the weld testing was finished by 8am.

"The pipe was handed back to the operations team at 2pm, which was ahead of schedule. We were supposed to finish by 4pm on Saturday and the actual construction was finished by 8am. It went extremely well.

"Our delivery partners Fulton Hogan, March Cato and Olsen Welding did a great job."

He was on site until 11pm on Friday and graduate engineer Epoki Vuki took the helm from 10pm until Saturday morning.

Martin says there is some reinstatement work being done that will be finished by the end of the month and will mark the end of the project.

"The team is now busy working on as-built drawings and asset capitalisation for this project."