This project involved transferring raw drinking water from the existing intake at the South branch of Giles Creek to Pond 3 of the Westport Reservoir network. The existing 2.5 km of reticulation consists of 4 hand dug tunnels linked by timber flumes and bridges, open channels and existing concrete pipework all in native bush land and protected wetlands. The longest of the tunnels which measures 1.2 km long and up to 200m deep, collapsed in the middle leaving the town without a water supply and relying on temporary pumping from a river below the reservoirs.
Using a series of trenchless techniques Hadlee & Brunton are installing approx. 1.5km of 630mm and 710mm PE through the existing reticulation. To reline Tunnel 1 a 40m deep portal excavation had to be undertaken. This was to expose where tunnel 1 and tunnel 2 intersected at the downstream end of Tunnel 1. At the other end (upstream end) a 40m cantilevered bridge had to be installed over a river to access where the tunnel exits a cliff face. A 1.2km long, 813mm dia. 360T steel pipeline is to be installed using a 500T Herrenknecht Thruster and a 200T Herrenknecht Maxi Rig. The existing intake weir is rebuilt and fitted with self-cleaning screens and solar powered Scada controlled automated gates and mag meters.
Article : governmentnews.co.nz
