27 June 2024:
Big raps to NZ Transport Agency Waka Kotahi, the Fulton Hogan team and our many subcontractors for completing the 2km rebuild of the Brynderwyns on SH1 in Northland in time for Matariki Weekend.
The Brynderwyns remediation was done under a four-month road closure (with a brief re-opening for Easter). A total of 115,000 hours were worked addressing 18 slips caused by Cyclone Gabrielle, one of which is pictured. Meanwhile, the two temporary alternative routes each added around 25 minutes travel time to and from Northland.
The highway was scheduled to reopen in mid-May, but a further slip in late April required additional geotechnical investigation, removal of a further 60,000m3 of soil and debris, and further batter strengthening work.
Around 10,000 vehicles travel the highway daily. Stakeholder Manager, Mel Norris, says there’s a mixture of relief and quiet jubilation in the team.
“There were so many pieces to this puzzle, and to pull it off in time for Matariki Weekend underlines the power of collaboration among the parties,” Mel says.
Road closure was chosen because of the extent of the slips, the narrow carriageway and for safety. A final layer of asphalt across the full width of the road will be added in late spring.
Enabling work began in October last year, with Fulton Hogan as lead contractor supported by Goodman Contractors (earthworks) and Geovert (stabilisation). Additionally, there were 20 local subcontractors.
The project included eight shotcreted retaining walls, strengthened by 136 steel ‘H’ piles driven to a depth of eight metres, and 400 soil anchors. The shoulders of the road have been extended on either side by a total of between six and seven metres.
More than 240,000m3 of earth was removed and a 24/7 online monitoring system was installed, with several sensors sending data to engineers via mobile phone. Sensors enabled a trigger action response plan (TARP) to assist geotechnical engineers assess the stability of the ground and the new batters.
