Kia ora and welcome to the June 2018 update from the Transmission Gully team.
With winter well and truly here, our winter works programme has commenced, meaning a change in focus from bulk earthworks to detailed earthworks such as bridge abutment walls, drainage, culverts and bridge foundations.
Here’s what’s been happening across the Transmission Gully project in the last month, and what’s coming up.
High strength PET foundation layers being placed south of Mackays Crossing – this is a very thick drainage liner.
Ground improvement work along the section north of Paekākāriki, to Mackays Crossing has been completed and the first pavement layer on the new coast road is nearly complete, ready for road paving work to start in a few weeks. The ground improvement process removes liquefaction prone material and replaces it with material that is much more stable in an earthquake. Work has been completed from just north of Bridge 2 and the construction of headwalls for a large culvert is underway.
At Bridge 2 the fill foundation treatment is ongoing. This is also to replace weak ground with strong material to ensure the ground under the bridge doesn’t liquefy in a large earthquake. Construction of the Mechanically Stabilised Earth (MSE) bridge abutments are nearly half complete and work on these will continue this month.
Temporary traffic management remains in place through this area, to provide safe working areas for our construction teams. Please take care and pay attention to the message boards. There will be further changes to the road layout in July, which we will coordinate with the road maintenance work being undertaken at Mackays Crossing by the NZ Transport Agency. We’ll keep you updated on works and what to expect closer to the time.
Bridge 2 fill foundation treatment.
Bridge 2 abutments – keystone block walls with mechanically stabilised earth backfill.
On Monday 25 June 2018, Capital Journeys (NZ Transport Agency) began upgrading Mackays Crossing on SH1. Scheduled for completion in mid-August, while the works are being carried out, only one lane is open in each direction. Please visit the Journey Planner website(external link) for more details.
Click on the map images to see larger versions.
Over the Wainui Saddle we are continuing with slope stabilising, concrete lined drains and permanent stream diversions.
Construction of the bridge deck and both settlement slabs is now complete for Bridge 6 over the Horokiri Stream, allowing us to start constructing the bridge barriers.
Reinforcing for the walls at Bridge 11 has been completed and the first concrete was poured last week.
Between Battle Hill and SH58 we are sealing many sections of motorway earthworks with a temporary surface to protect it for winter. The bulk earthworks will be more or less shut down for the winter with only the detailed earthworks such as MSE walls, drainage, culverts and bridge foundation work continuing. The temporary surface will protect the sections already at subgrade level from the wet weather and allow us to use them as haul roads if required.
Alongside SH58, the work on the new section of highway and the bridges for the interchange continues. We have relocated power lines and Vodafone services in preparation for the switch over to the new alignment later in the year. Drivers will notice that the speed limit has reduced to 50kph as there is now no shoulder and cyclists need to share the traffic lane. Please take care and follow the signage.
Heading south through Belmont Regional Park down past Cannons Creek Bridge as far as the Ranui Forest we are sealing areas that are already at their final earthworks level so they are protected during winter ready for paving layers to be placed in summer. Much like the Battle Hill area, our winter works programme focusses on detailed earthworks rather than bulk earthworks.
Looking south – Wainui Saddle shotcrete and soil nails to stablise slopes.
Section 4 of new Te Puka stream channel being constructed.
Earthworks underway for the motorway beside Section 4 of the new Horokiri Stream channel.
Bridge 6 over the Horokiri Stream in the Battle Hill area.
Bridge 11 side wall reinforcing steel.
Major culverts being installed south of James Cook Interchange, which we refer to as Bridge 17 due to their size.
The foundation construction of Pier 2 is now complete, and we have started construction of the column. Formwork will be installed around the steel to hold the concrete in place while it sets. We have three more concrete pours for the Pier 1 foundation and then the next stage will be to start work on the column that will rise from the pier foundations to support the beams and bridge deck, nearly 60 metres above.
The foundations at Pier 2 (south side) with the column reinforcing steel ready.
A night concrete pour in progress at Pier 1 (north side of Cannons Creek).
In the launch yard, we have completed the assembly of all the permanent steel girders (or beams) for the first launch from the south abutment to Pier Two in early spring.
24-metre long, 53-tonne steel girders in the launch yard. The crane in the valley floor and the north abutment can be seen in the background.
View the animated video below to see how the launching process works.
At Kenepuru Drive we have completed the impact wall between the rail corridor and the bridge columns. This is a large wall that will protect the bridge columns in the event of a train derailment. There is also an isolation wall beneath the rails beside the Porirua stream to prevent any lateral movement of the rails damaging the bridge in the event of an earthquake.
The Bridge 28 impact wall beside Te Ara Tawa pathway.
In this same area we have completed the fill foundation improvements (removal of liquefiable material). The team that will build the MSE walls to connect the roundabout to the bridge will be mobilised in coming weeks.
Construction of the MSE walls for Bridge 25 (the northbound flyover across State Highway 1 to get onto the Transmission Gully motorway) is ongoing. Abutment A on the west side of SH1 has been completed. The headstock (the big section on top of the column like the horizontal line on the letter T) for Bridge 25 Pier 3 has been erected.
On the southbound side of SH1, works to realign lanes towards the eastern side is underway. Moving the lanes over will provide more space for us to work in the median while erecting the central columns for Bridge 27. This work will be done at night, where a single lane in each direction will be in place at a reduced speed of 70km/h. Please take care if driving through the area.
Over the next few months we will be carrying out a number of night activities throughout this zone. For safety reasons we need to close lanes to carry out this work and this can only be done at night in this area to minimise traffic delays during peak times. We are aware that night work can be disruptive to nearby residents and we apologise for any disturbance. Please call us on 0800 TGINFO or email info@tg.co.nz if you are having problems or would like more information on what we are doing.
Preparing to switch southbound traffic over to the new section of the Collins Ave overbridge (Bridge 26) is a key focus for us. The northern approach embankment has been completed to subgrade level and is ready for paving, and the southern approach is very nearly complete. The work to finalise this section for vehicles will continue through July. Once the traffic is switched over, we will begin on the demolition of the current bridge. This is scheduled to happen in September. We will provide more information on this important milestone in upcoming Construction Updates and the website.
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