Construction of the Scheme

 

Construction of the scheme involves:

  • Upgrading of the existing track from the road end to the west branch of the Matiri river.
  • Construction of a ford across the west branch of the Matiri river.
  • Upgrading of existing track from the west branch to the power house.
  • Construction of a new track from the power house site to the lake outlet.
  • Installation of the penstock either beneath the track or above ground on bearers alongside the track. Above ground installation of the penstock will be predominantly within the forest.
  • Temporary lowering of lake Matiri and construction of concrete outlet weir structures. A temporary coffer dam will be used to aid construction of the main and largest weir containing the penstock, spillway and fish pass structures. Concrete for the two smaller weirs will be delivered by helicopter to minimise site damage.
  • Installation of a small control hut at the main weir.
    Installation of the 1.6M diameter penstock.
  • Construction of power house and tailrace.
  • Construction of new transmission line from the end of the existing Network Tasman line to the power house.

It is estimated that construction of the scheme will span 12 months. An excavator will be used for the majority of the earthworks and concrete will be produced at a temporary batching plant established on New Zealand Energy land and delivered to the required location by truck or helicopter.

Humus and duff material will be stockpiled during initial vegetation clearance and replaced on exposed areas of soil such as cut batters in order to ensure rapid reinstatement of native plant cover.