11 October 2019
What’s the problem with the bridge?
The bridge was built of reinforced concrete in the 1950s. Condition assessment of the bridge in 2017 found that the concrete was breaking up due to corrosion. Reinforcing steel inside the concrete is deteriorating and weakening the bridge.
What is Council doing about the problem?
We have engaged structural engineers and specialist contractors Freyssinet to repair the bridge while maintaining vehicle and pedestrian access across it. Contractors will first remove damaged concrete using hydro-demolition (high pressure water jets). Next, they will repair the corroded steel and install a corrosion protection system, and finally repair the concrete.
How long will the repairs take?
Repairs are expected to take about six months, until March 2020.
Traffic barriers and temporary support beams have already been installed on the surface of the bridge. Over the next few weeks, contractors will put up scaffolds under the bridge to allow safe access for repair work on the underside of the bridge.
Why will the repairs take so long?
To repair the bridge, contractors need to put a temporary steel structure above the bridge. This structure will support the beams underneath the bridge while they are being repaired so the bridge can remain open to traffic. This approach means the works need to happen in stages. For safety reasons, each stage allows only a limited amount of work space, so contractors can't work on all the beams at the same time. The bridge has four beams, all of which need repairs.
Why can’t contractors work 24/7 to have the bridge completed before summer?
Contractors are dealing with several constraints. They are working over water and space under the bridge is limited, so they can only work on one beam at a time. Tide levels restrict the hours available each day to carry out the repairs, with access to the working platforms under the bridge restricted at high tide.
In addition, contractors are not working at night because the repairs would be too noisy and disruptive for the community.
Will the bridge close during repairs?
The bridge will remain open for most of the time, but there will be three 48-hour closures. The first will take place early to mid-November, the second in mid-December and the third in late January. We need to close the bridge after new concrete is poured to give it time to strengthen. During this time, the bridge will be closed to all vehicles.
Noticeboards will be placed on either side of the bridge one week before closures, and we’ll inform you through the Kaipara District Council website, Facebook page, and our Antenno app.
Will there be a detour route while the bridge is closed?
During the closures, local light traffic will be diverted along Cames Road. Security will be in place to make sure heavy vehicles do not use Cames Road. We are also improving Cames Road’s carriageway and drainage.
Long distance and heavy traffic will be diverted along State Highway 1 and the Kaiwaka-Mangawhai Road.
Why is only one lane open to traffic?
The corroded steel in the concrete beams has weakened the bridge. Having only one lane open to traffic reduces the weight on the bridge.
How do the temporary traffic lights work?
The traffic lights installed on Tomarata Bridge works comply with NZTA’s Code of Practice for Temporary Traffic Management. The lights have vehicle sensors, which activate the green light to allow traffic through one side at a time. The traffic lights have been pre-programmed with a “Stop – Stop” phase where both sides show red lights for safety. The length of this phase is based on the distance between the two lights.
What will be done about the traffic during the holiday period?
We hope to open the bridge to two directions of traffic over the three-week Christmas holiday period. However, for that to happen we will need to have completed repairs to three of the four beams and have checked the fourth beam to make sure the damage is not too bad. We hope to have better knowledge of this in early November and we’ll update you as soon as we know.
The bridge will need to be put back to one lane of traffic at the end of the three-week Christmas period and until the contract has finished.
We are also working hard with NZTA to minimise disruption and traffic hold-ups. The route to Mangawhai via Kaiwaka will be strongly promoted before and during the summer period.
What about the school/students?
We’re liaising with the school to manage the safety of pupils during the closures to assist with easing disruptions. There will be a safe route across the bridge for students and parents.
Will there be pedestrian access across the bridge during the works?
Pedestrians can cross the bridge but may occasionally have to be escorted for safety reasons.
Will the repair work be noisy?
Part of the work involves removing corroded concrete by using high-pressure water jets. This type of work, known as hydro-demolition, can be noisy. Contractors will use a noise blanket around the site to reduce the noise, and no work will be done at night.
Hydro-demolition for two of the four beams will begin on Monday 14 October and last for about three weeks. Further hydro-demolition for the other two beams will take place within six months.