Pump Station 15 (PS15) is the second largest pump station in Christchurch responsible for pumping wastewater from Woolston and the surrounding hill suburbs to the Christchurch treatment plant for 11,250 residential and 3700 commercial household equivalents. PS 15 was damaged during the 2011 Canterbury earthquakes suffering uplift which severed the main incomer delivery pipes and seriously compromised the station’s ability to operate. Emergency repairs were carried out which were sufficient until a permanent fix could be affected. In 2016, a major upgrade and rebuild of the pump station was undertaken under the SCIRT programme.

Martin Civil Construction undertook

• • Constructing a new incoming sewer bifurcation chamber
  • Construct two new 1200 dia PE incomer mains
  • Refurbish and line the existing wet wells
  • Replace the existing pressure mains and valve chambers with new 650 dia PE mains
  • Construction and fit out of a steel portal frame / precast concrete panel pump station building over the existing caisson structure
  • Construction and fit out of a precast concrete building to house a new standby generator
  • Construction of a large biofilter

Key challenges

• • Dewatering and sheetpiling to 8 metres deep
  • Working around deep grout pile ground strengthening
  • Managing and over pumping sewer flows up to 500 l/s
  • Constructing a new building over a working pump station
  • Managing constant design changes