By Lynda Myer
Following leaving the southern shore of the Manukau in September and excavating the 1500m stretch beneath the harbor in just 11 weeks for the Central Interceptor project, the TBM Hiwa-i-te-Rangi with 5.4m diameter on 6th December reached at the 25m deep Pump Station 23 shaft in Hillsborough (Auckland).
While currently the TBM cutterhead is going to be inspected, repaired and adjusted, the date of commencing tunneling process on the 2 km towards central Auckland to Keith Hay Park site in Mount Roskill by TBM Hiwa-i-te-Rangi will be 2023.
Starting her journey in August previous year, Hiwa-i-te-Rangi has now travelled over than 4 km from the site next to Māngere Wastewater Treatment Plant on Greenwood Rd to Onehunga, crossing through different geological formations. Using concrete rings this 4.5m diameter tunnel is created and it formed by six concrete segments that are fixed together underground, whereas 10-12 completed tunnel rings are laid each day. In order to removing spoil through the cutterhead, along the length of the nearly 200m TBM a series of conveyor belts are being used, before tipping into muck skips which travel to the tunnel entrance via electric locomotives. A gantry crane lifts the muck skips out of the shaft and the spoil is deposited at nearby Puketutu Island.
Also, the third success of the micro-TBM Domenica on the Link Sewer C, the first link sewer (running from May Rd, Mt Roskill to Avondale) was marked. In November it completed an epic 1100m drive and broke through at Miranda Reserve site in Avondale.
Following travel of 300m to the pump station located further west in the Reserve, Domenica will complete the Link Sewer C. It will then be refurbished ahead of work on the second link sewer next year.
Responsibility of delivering the Central Interceptor project is up to Ghella Abergeldie JV and location of advancing tunneling process is at 15-20m below the seabed, with a maximum of 15 crew working 24/7 underground at a time.
According to Auckland Council’s announcement earlier this year, in order to capturing combined wastewater and stormwater flows in Herne Bay, the Central Interceptor tunnel would be extended from Tawariki St, Grey Lynn to Pt Erin. Consent applications for the tunnel extension will take place early next year.
