Rangipo Tunnel Repair

In 2010 MAP Projects was the first contractor to successfully complete the dewatering of the 40m deep, 4.5m diameter and 3km Rangipo Outfall tunnel in over 30 years. The Project for Genesis Energy and was completed in 8 days as part of a 14 day planned shut.

  • Preparation works were critical to the success and MAP worked closely with our preferred Generator and Pump Supplier NES to identify submersible pumps appropriate to task (we located 3 of the 4 pumps of this size available in the country and had them serviced and made ready).
  • MAP made a purpose built lowering frame to mount the pumps for lowering the 120m down the tunnel decline. HDPE was progressively joined as the tunnel was lowered to maintain outflows as the pumps were lower. Small access steps were added to allow for safe access to the base of the decline.
  • The project was run 24 hours a day with a skeleton crew maintain the pumps and generators through the night. Trolleys and a lifting frame were used to manoeuvre one of the pumps a further 60m into the tunnel to a dewatering sump. The water was lowered to ankle deep and allowed the tunnel inspection to be completed 5 days ahead of schedule.