Wellington sinkhole repair estimated to cost $5m

It’s estimated the cost to repair and replace a 100-year-old pipe in central Wellington will amount to $5m.

In February a sinkhole opened up on Jervois Quay after the stormwater pipe collapsed, risking the safety of drivers and increasing the risk of flooding in the CBD.

Crews initially installed a temporary fix and backfilled the sinkhole, allowing for Jervois Quay to be reopened while a permanent solution was investigated.

Over the following months work was undertaken to try to repair the pipe without the need to dig a trench the full length of the road to replace it.

But a subsequent attempt to replace a temporary section resulted in the pipe collapsing even further.

In the end, the pipe had to be fully replaced in a planned marathon effort.

All six lanes of Jervois Quay were closed for a period over Queen’s Birthday weekend, which allowed Wellington Water crews to embark on a 24/7 operation.

It was so effective commuters were able to drive through two lanes, both northbound and southbound, 36 hours ahead of schedule.

The council’s Quarter 3 report, which covers the first three months of this year, estimated all the work will cost $4.9m. The final invoices are still coming in.

Broken down, $4.3m is expected of capital expenditure and $0.6m of operational.

The figure is listed as a forecast overspend for the following quarter.

The council’s Infrastructure Committee chairman Sean Rush said a cost was always going to be on the books because the pipe would need to be renewed at some stage.

“It probably should have been renewed a year ago before it did. To say we got the maximum use out of it would be generous I suppose.”

Rush said extending the replacement work over the course of six weeks, without completely closing the road, would have cost more.

“You’re much less effective because you’ve got to keep closing the hole and opening it. There is also more interruption to business and traffic management.”

The quarterly report also points to 218 dry weather wastewater overflows, falling well short of a zero target.

“We continue to observe sewerage overflows caused by fat and sanitary product blockages, deteriorating pipes and tree rot intrusions across the region”, the report said.

Active replacement of vulnerable pipes and a prompt response to reported incidents remain Wellington Water’s primary methods to manage these overflows.

But the report also said Wellington Water frontline staff are being “stretched” with the overall workload for reactive repairs further increasing over summer.

Drainage blockages and overflows accounted for almost half of the wastewater network jobs.

Meanwhile, leaking pipes and tobies remain the most prevalent issues across the city, accounting for more than 76 per cent of water supply jobs.

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