Waka Kotahi Wellington Regional manager Mark Owen talks us through the work required to clear the slip zone on State Highway 59 north of Pukerua Bay, which will reopen on Thursday. Video / Mark Mitchell
The former main route in and out of Wellington is expected to reopen this week after a massive slip forced a weeks-long closure.
The slip would have crippled the capital had it happened at the start of this year, before Transmission Gully provided an alternative route for traffic, reducing the traffic movements for the road by nearly 20,000 per day.
The clean-up, repairs, and future-proofing of the site are estimated to have cost $3-4 million.
Contractors have been working day and night at times over the past three weeks to clear 25,000 cubic metres of earth on and above the picturesque coastal road on State Highway 59 last month.
A bench has been created above the road to hopefully catch potential future slips. Photo / Mark Mitchell
Waka Kotahi regional manager Mark Owen said the amount was in excess of 3000 truckloads.
The whole road has been closed since the slip happened on August 19, but Waka Kotahi today announced they were planning to reopen it this Thursday.
Transmission Gully, which opened in March this year, has allowed Waka Kotahi to fully close SH59 for repairs and slip-clearing, instead of trying to keep a lane open for traffic, thereby slowing down the process substantially.
"We've always known this is a vulnerable section of highway from a resilience perspective," Owen said.
It is not uncommon for the road to be hit by slips, be damaged by waves in stormy weather, or be blocked off completely by car crashes, all incidents which plunge commuters into traffic chaos.
Waka Kotahi regional manager Mark Owen said the road is planned to reopen on Thursday. Photo / Mark Mitchell
"I think it just goes to show that the right decision was made [to open Transmission Gully]," Owen said.
The road used to have about 23,000 traffic movements a day, Owen said.
"The opening of Transmission Gully has seen those numbers reduce substantially. After the opening of Transmission Gully, they fell to around 6000 a day."
After the slip, the slope's stability posed a real risk, so it was decided it was best to do a long-term fix to give the highway maximum protection, he said.
A "significant crack" was discovered in the hillside.
Contractors cleared the area and "benched" it, meaning potential future slips will hopefully land on the bench, rather than continue on down to the road.
"The size and scope of this work have meant the closure has lasted weeks, not days. However, the earthworks that have been done, the new slope benching built, and other associated improvements mean this stretch of State Highway 59 is much stronger and better protected for the future."
The major roadworks site at the Pukerua Bay slip zone on State Highway 59. Photo / Mark Mitchell
While the road has been closed, Waka Kotahi has also used the opportunity to do maintenance across the whole stretch between Pukerua Bay and Paekākāriki - clearing trees, repairing road surfaces, and so on.
State Highway 59 will reopen to all traffic at 5.30am on Thursday. There will be a 50km/h temporary speed limit in place, covering the slip site and an adjacent area where footpath repairs are being done. This work will continue in the area over the coming weeks.
• About 60 staff from 20 sub-contracting companies worked at the site over the last three weeks. The work site was operating 24/7 over the final few days.
• 25,000 cubic metres of material removed (this included helicopter work).
• The construction of benched slopes (similar to those in Ngauranga Gorge) to help mitigate any future slips.
The repair and safety works at the site have been going on for weeks. Photo / Supplied
• Installation of streetlights, safety barriers and painting of new road markings.
• Cleaning and maintenance of adjacent culverts, weed spraying, vegetation/tree clearing, and road sweeping.
• An estimated $3-4 million is being spent on the project. Exact costs are being finalised.
