Steel Multi-plate™ culvert the first and best choice for 500+ home subdivision

An 84.5ha rural site on the western side of the Grand Drive motorway exit in Orewa’s West is under development and will eventually be known as Ara Hills subdivision. The land is being developed by Hobsonville Point developers, AV Jennings and is expected to eventually provide 575 residential lots as well as space for a commercial centre. The land was originally part of a 253-hectare property known as Hall Farm.

Michael Lee, Aireys Consultants says the aim of the design of the subdivision was to entice would be home-owners with sweeping roads that undulate through the subdivision offering a more desirable location for their new homes.

With the topography of the site variable and with three streams requiring protection, Michael looked at bridges and culvert options to traverse the streams and create an interesting, appealing landscape.

“We looked at concrete bridges and concrete culverts and settled on a Steel Multi-plate™ from CSP®,” says Michael. “There are several reasons for the choice. There’s a considerable cost saving on a concrete bridge versus a Steel Multi-plate™. It’s about half the cost due to the speed of installation and the culvert itself. Another factor is the ecological protection we could offer using a Steel Multi-plate™. As part of the application we needed to protect the streams with the construction of any road crossings.”

Michael says the third consideration was the flexibility of an arch culvert in its positioning. “We were able to lower the culvert down to the stream bed so the road and people come right down in amongst the trees. With the extensive planting that will finish off the culvert it will create an impressive, appealing entrance and sense of occasion for future home owners.”

With three culverts included in the Resource Consent for the development Richard Bresgi, Project Manager from Dempsey Wood (the contractor appointed to the development) talks about the first installation.

“The first Steel Multi-plate™ is 43m long but only 2.6m high,” says Richard. “We have installed Steel Multi-plate™ from CSP® before so are familiar with them. It’s gone together really well. This has been the quickest installation of a Multi-plate™ we have undertaken taking just five days. Auckland’s good weather helped.”

Richard says they diverted the small stream and have had no problem in assembling the culvert. Back filling of the arch is almost complete - layered evenly on either side as they progressed to ensure the Steel Multi-plate™ retained its shape throughout the process.

“Once the planting is in place this option will show it had the least impact on the site and created the most interest and appeal,” says Michael. “Multi-plate™ culverts are a good, flexible, cost effective culvert option for locations such as this.”

Developer:AB Jennings
Designer:Airey Consultants
Contractor:Dempsey Wood
Location:Halls Farm, Orewa
Development:Ara Hills Subdivision
DateJune 2020

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