When "Too Hard" Is Not Acceptable – Marine Parade Wastewater

Annual Conference

When QLDC went to market for the 3 Waters O&M contract in 2014, it was with an expectation that the contractor would accept shared risk, be “frank and fearless” as a trusted advisor to council, and display the management courage to respectfully and persuasively challenge QLDC decision making. In this new contractual culture, it was no longer adequate for the contractor to merely notify council of the nature of the risk; it has required the contractor to engage closely with council to ensure that the risk is communicated at the right levels, and collaboratively develop a solution.

One such risk has been associated with Marine Parade Wastewater Pumpstation. This pumpstation is located in central Queenstown in an area of extremely high public amenity, environmental sensitivity and historical significance. All year round the area is full of tourists enjoying the lake and mountain views, taking jet boat rides or pleasure cruises, shopping or visiting the botanic gardens.

The pumpstation takes wastewater from a large percentage of Queenstown – from Sunshine Bay, Fernhill, Arthurs Point and the CBD. With limited options to increase pump station capacity, the average flow of 80 L/s means that the pumps run every three minutes, and the wet well has only seven minutes storage.

Recognising the critical risk of this asset, Queenstown Lakes District Council (QLDC) and Veolia have implemented a number of measures to ensure redundancy in the pumps, control gear, telemetry and power supply over the years. However, the mild steel risers, manifold and asbestos cement rising main have always been single points of failure and solutions have always been put into the “too hard” basket. This has been due to the considerable constraints on site:

  • A pristine local environment
  • High public amenity values and crowded public area
  • Noise sensitive neighbours with the Novotel being directly adjacent
  • International profile, especially if something goes wrong
  • High water table
  • Loose unconsolidated gravels
  • Numerous historically significant trees over the pipe alignment.
  • Operational constraints due to only seven minutes’ storage being available
  • The culture built during the O&M retender process has driven greater focus to develop a robust solution, and made it unacceptable to continually defer action. This paper describes how a solution has been developed and is being delivered. Central to this has been close partnership between Veolia and QLDC technical staff, and early contractor involvement to carefully work through construction methodology and work sequencing. Project risks have also been controlled through innovative technologies such as laser scanning, hydroexcavation and slip-lining. These technologies have enabled precise fabrication of parts, minimizing worker time in hazardous environments, have eliminated all silt mobilization into the nearby Lake Wakatipu and Horne Creek and have limited disruption to the public through avoiding extensive open trenching.

    Regardless of the significant challenges and constraints and increasing scope, the project was successfully delivered in June 2018 for $820 k.

    Conference Papers

    WHEN “TOO HARD” IS NOT ACCEPTABLE – MARINE PARADE WASTEWATER UPGRADE.pdf

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    26 Sep 2018