Work ramps up at Waikanae River Bridge site


The NZ Transport Agency is advising Kapiti locals that activity at the Waikanae River Bridge will be ramping up next month, with a big focus on protecting the Kapiti community from flooding.

The M2PP Alliance will be undertaking with river channel works, bridge beam placement and an extensive winter planting programme.

The river channel works will both protect the new bridge and provide significant flood protection benefits to the Kāpiti Coast District and the Greater Wellington Region.

The river channel works include:

  • removing vegetation and widening the river channel near the bridge
  • stabilising the river channel under the bridge
  • armouring the bridge foundations and banks with rock to protect against flood damage.

Mackays to Peka Peka Expressway Project Manager Alan Orange said vegetation clearance will begin after Waitangi Weekend with the removal of large trees and other vegetation in preparation for channel widening. Before excavations begin on each side of the channel, a protective wall of river shingle will be built around each works area. The protective walls will minimise water flow through the work sites.

Mr Orange said it will be unsafe for river users to float or paddle through this area after Waitangi Weekend 2016, until the works are completed in April 2016.

“We’ll have staff monitoring the river upstream while machinery is working. Flags will be strung across the river channel to mark the boundary of the works site. Anyone floating towards the work site will be asked to leave the water, for their own safety.”

Under the bridge, excavators will lay rock ‘armour’ to protect the bridge foundations and the river banks. As well as protecting the bridge from debris erosion, the armour will also help prevent flooding by helping the riverbanks hold firm.

Mr Orange said 7300 cubic metres of river shingle and silt will be removed from the site, and 3000 cubic metres of rock imported to ‘armour’ the bridge and channel.

The northern river path will be diverted for approximately 300m where it travels under the new bridge, to ensure the safety of river path users.

“The work is being carried out when river levels are low to allow us to do some work in the river channel. As a result, the river water will be discoloured at times, but this is nothing to be concerned about. Discoloured water outside the works area remains safe for swimming, because it’s just riverbed sediment that has been stirred up a little.”

Excavators will build protective walls of river shingle around each works area before excavations begin.

Once the river works are complete, large beams will be transported to both banks for lifting and placing on the bridge crossheads. Beam placement could take several months.

From June, 10,000 new plants will be planted in the cleared areas. The majority are native species grown from locally sourced seed. Species include kānuka, mānuka, flax, toetoe, coprosma, karamū, korimiko, ngaio, matipo, kohekohe, māhoe and whauwhaupaku (five finger). Willow will be planted in some areas to protect banks from erosion.

River paths will remain open during the river works, but there may be brief delays of a few minutes during tree felling.