The new bridge
Work on demolishing the existing bridge will begin in February 2013 followed by piling foundations and then construction work on the beams, deck and footpaths for the new bridge. Temporary bridges have been installed and traffic diverted to them in late January 2013.
Completion of the new bridge is likely to be by mid 2015, but timeframes may have to be adapted if unexpected ground conditions for piling are encountered.
The demolition of the existing bridge will begin in early February 2013 and should be completed by early May 2013.
The piling process for the new bridge will take about 15 months and start as soon as the existing bridge is demolished.
The existing Ferrymead bridge was being strengthened and widened when the February 2011 earthquake struck. The quake caused significant damage to the existing structure and liquefaction in the riverbed. Council has subsequently agreed to demolish the existing bridge and build a new bridge which will meet 100 per cent of the new building standard.
History of this project
In 1994, a 'Lifelines' study was undertaken to review a number of bridges on key routes around the city, which included the Ferrymead Bridge.
The 'Lifelines' report identified that in the event of a significant earthquake, the soil beneath the bridge could liquefy, and because the piles aren't currently founded to bedrock – there is a risk of bridge failure (this liquefaction occurred in the 22 February earthquake, and resulted in significant damage to the bridge foundations).
In 2004, Council presented the Ferrymead Bridge Lifelines Project concept plans to the public through online and print communications, as well as a public meeting of approximately 100 people. Council received approximately 200 responses to the plans, and of those, 70 percent were in support of the plans.
The project then underwent an immense design process over five years. This was so that the most cost effective upgrade will be carried out in the least amount of time and with minimum disruption to bridge users.
As a result of changes to the ground conditions in the vicinity of the bridge resulting from the February earthquakes, it became unfeasible to install the planned foundations.
This is because the ground has been disturbed, liquefied, and is very easy to re-liquefy. Council subsequently agreed to demolish the existing bridge and build a new bridge which will meet the new Building Code.
Frequently Asked Questions about the Ferrymead Bridge – 29 January 2013
Why is the Ferrymead Bridge project important?
Ferrymead Bridge is a lifeline providing a vital transport connection to the eastern suburbs and the port of Lyttelton for overweight and over-dimension loads. It also carries vital water, sewer, power, phone and other services. This project will make sure that the connection remains usable in the event of a future significant earthquake and will provide additional capacity that will subsequently enable a Bus Priority lane on the Sumner route. The project improves safety for pedestrians and cyclists through the area.
Ferrymead Bridge carries about 30,000 vehicles per day and serves 11,000 people, 4,450 households, or about 3.5 per cent of Christchurch residents, and carries water, pumped sewage mains, telecom, and power services.
What is the New Zealand transport Agency’s role in this?
New Zealand Transport Agency (NZTA) has provided $22.12m towards the cost of the project. The NZTA is playing a critical role in the recovery of Christchurch through its funding, as part of the Government's partnership with the City Council, the repair of the roading infrastructure damaged by the earthquakes.
This is part of the NZTA's One Network approach to ensuring there is a transport network that enables ease of movement between places by safe, efficient and resilient links, and offers travel choice for residents.
Who has been awarded the tender for carrying out the project?
HEB Construction Limited brings extensive experience to the project and have worked with the Council and Opus International Consultants to develop a new bridge design. They have also undertaken work on temporary infrastructure, diverting wastewater, power and water supply on to the temporary bridges and the approach roads.
What is the cost breakdown of the project?
The total cost of the project is $34.87M of which the New Zealand Transport Agency (NZTA) has provided $22.12 M.
Ferrymead Project Cost Breakdown
Cost to date: (Including original design, consent, partial construction, Earthquake Recovery works, detailed geotechnical investigations, new design, traffic and services diversions to rebuilt temporary bridges) $9.55M
Construction including demolition of the old bridge and new approach roads and new service connections $21.39M
Provisional sums including insurance costs, construction monitoring and contingency. $3.93M
What challenges are there for the bridge foundations?
The ground conditions at Ferrymead are particularly challenging which has added significantly to the cost. Design standards for structures and buildings have increased, resulting in the need to strengthen the foundations of the new bridge to meet these new post-earthquake standards. At Ferrymead the underlying rock slopes from Mt Pleasant towards the city. This means that the loadings from liquefaction on each abutment are uneven, making the design for the bridge and the piles complicated. The following stylised drawing shows the bridge and underlying ground conditions.
What have geotechnical investigations revealed?
Extensive and detailed geotechnical investigations were undertaken in the locations of the new piles for the new bridge so that an accurate understanding of the underlying rock could be known. This has shown that the underlying rock is extremely variable with some layers being very weak, resulting in the piles for the new bridge having to be founded about eight metres into the underlying rock to enable adequate support to be gained for the structure.
How long will it take to build the new bridge?
After the temporary bridges are connected the old bridge will be demolished. This is expected to take about three months. Piles will then be driven into the riverbed to a maximum depth of 20 metres. The piles will go through sand and mud and then be driven a further five to eight metres into bedrock so that the bridge meets new safety requirements. This is a difficult and complicated job. It will take about 15 months. Construction of the rest of the bridge will then take about another year. The whole infrastructure upgrade will take about two-and-a-half to three years.
What disruption will the work cause?
The temporary bridges provide one-lane traffic in both directions, so traffic disruption will be minimal. Motorists are requested to follow road signs. There will be no disruption in telecommunications, water, sewage transfer. These services have already been secured to the temporary bridge’s and will remain in place until construction of the new bridge is complete.
Demolition and piling work is noisy and can cause vibrations. Work will be carried out from 7 am to 6 pm on weekdays, 7 am to 12 noon on Saturdays with shorter hours during winter. This work will cause disruption and is necessary to maintain the lifeline to the city.
How strong will the vibrations be?
The vibrations will be noticeable for people in buildings close to the construction work. In terms of magnitude and intensity it cannot be compared to the earthquakes which had epicentres in the region.
How are we protecting the environment?
The estuary and river environment are important to us. As part of the demolition process slabs of rock are placed under the bridge and will catch concrete and other particles as the bridge is taken down. This is then collected and taken to Kate Valley Landfill. The current state of the estuary will not be affected by the work.
Did you know?
The bridge will be supported by 10 piles. Each pile is about the height of a seven storey building – 25 metres (the height of eight red buses stacked on top of each other).
Each pile weighs about 50 tonnes. The smallest are 1.1 metres in diameter and the large ones are 2.4 metres.The bridge will have about 300 tonnes of reinforcing steel.
There are 26 Super T-Beams which make up the final stage of construction. Each one weighs 45 tonnes.
The machines used to demolish the old Ferrymead Bridge weigh 12 tonnes and are called “nibblers”.
The temporary bridges can carry loads of 150 tonnes – a car weighs less than a tonne, a truck weighs 5-10 tonnes.
How you can find out more
Take a look at these information sheets.
A public drop-in session will be held at the Mt Pleasant Yacht Club on Tuesday 29 January 2013, 4pm to 7pm.
Visit this page for updates.