July 15, 2013

Work begins on new Rangiora stopbank

Environment Canterbury has started work on a new $2.1m stopbank on the Ashley River in the Cones Rd area on the northern outskirts of Rangiora.

The 2km stopbank will be constructed in two stages on land owned by Environment Canterbury, the Waimakariri District Council and A&P Showgrounds. It will run between River Road and the existing Ashley River stopbank, and extend from West Belt to the Railway Bridge.

The contract for the first stage of the work has been awarded to David Morris Earthworks, starting a kilometre upstream of Cones Road to Milton Avenue.

“This stage will be completed by September, and the second stage – extending from Milton Ave to the Railway Bridge embankment – is expected to be put out to tender in 2014, and completed by April 2015,” said Ian Heslop, Principal River Engineer, Environment Canterbury.

He said the stopbank upstream of the Ashley River Bridge at Rangiora was known by locals as “Break-Bank” because it breached on eight occasions between 1868 and 1953.

“That section has been significantly strengthened since 1953, however it is still considered a risk. The new stop bank will capture breach flows, returning them to the Ashley River upstream of the Railway Bridge.”

This would reduce flood risk for Rangiora, Woodend, Waikuku and Kaiapoi, he said.

About 50,000 cubic metres of gravel fill for the new stopbank is being brought 13km from a stockpile on Mount Thomas Road. The gravel could not be extracted from the nearby riverbed because this could further damage the Rangiora Bridge piers.

A new $11m bridge is planned and will take more than a year to build. It will be jointly funded by the Waimakariri District Council and the New Zealand Transport Agency (NZTA).

Mr Heslop said the new Ashley River Rangiora stopbank design has been developed in consultation with Waimakariri District Council and NZTA engineers to ensure it is compatible with the proposed Rangiora Bridge replacement.

ENDS

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