A dynamite idea2 min readReading Time: 2 minutes
A dynamite idea ?
Not possible says Waka Kotahi NZTA
The coffer dam in place for construction of one of the bridge’s main support piers. On the left is the staging platform for cranes and other equipment to move about on while the bridge is under construction.
At the beginning of August, the Onehunga Community News received an email from one of our readers, who questioned why the new Mãngere Bridge is being constructed alongside the Old Mãngere Bridge, when, “ it might have been cheaper to get the army and navy to just blow it up and crane it away? A lot of us are following the slowness of the construction and the time taken to date, and wonder what the completion date is.”
The Onehunga Community News contacted Waka Kotahi NZTA, and their senior project delivery manager, Andrew Thackwray, responded as follows:
“Demolition of the bridge by blowing it up, as your reader suggests, was not considered a viable option for both environmental and safety reasons. Many of the bridge’s old reinforced concrete beams are in a brittle and crumbling state. As the beams are removed, they will be transferred into skips on a barge to ensure none of it falls into the water, which would be a potential safety hazard for recreational boaties and ships using the harbour.
The main environmental risk is from concrete cutting slurry (a mixture of sand, cement and water), dust and small pieces of debris falling into the water, so a special machine vacuums it all up during demolition.
We know that the old bridge has a long history and is well loved by the community. A salvage plan has been created with Heritage New Zealand for elements of the old bridge to be incorporated into the nearby landscape to ensure the heritage of the old bridge is not lost.
The demolition of the old bridge and construction of its replacement is happening simultaneously so the new bridge can be opened as soon as possible to restore a valued walking, cycling and fishing connection for the Māngere Bridge and Onehunga communities.
Work on the bridge is continuing under COVID-19 Alert Level 3 with strict health and safety protocols to ensure the safety of our workers.
The scheduled construction of the bridge in approximately two and a half years is normal for a structure of this complexity and size over water. The COVID-19 Alert Level 4 lockdown earlier this year caused minor delays in the construction schedule and the team is working hard to make up this time. Barring further COVID-19 disruptions, the expected completion date is 2022.”