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Watercare opens EOI for Central Interceptor wastewater project

Watercare opens EOI for Central Interceptor wastewater project

Water utility Watercare is seeking expressions of interest (EOI) for construction of the new Central Interceptor wastewater project in Auckland, New Zealand.

Bids will be invited for the construction of the Central Interceptor in two stages:

  • EOI – open from 20 October 2017, and will pre-qualify up to four contractor consortia.
  • Request for Proposal – held during 2018, to award a contract for construction of the works.

The EOI will be released via Watercare’s e-procurement portal, TenderLink.

Once completed, the Central Interceptor will increase the capacity of Auckland’s wastewater network.

An earth pressure balance (EPB) tunnel boring machine (TBM) will be used during construction, linking the 4.5 m diameter pipe to 4.4 km of sewers, ranging in size from 2.1 to 2.4 m in diameter.

The tunnel will be constructed between 15 and 110 m underground and will run for approximately 13 km between the suburbs of Western Springs and Mangere.

The TBM will be driven through weak sandstone and may encounter mixed face materials in Auckland’s geology, which is overlain with volcanic soils and rock.

The southern end of the tunnel will extend through marine and alluvial sediments, and then under the Manukau Harbour.

The main tunnel will terminate at a lift pump station that will be constructed at the Mangere Wastewater Treatment Plant.

Shafts for the station will be constructed using a D-Wall method and feature a dual cell configuration approximately 40 m deep; the cells will be 12 m and 26 m in diameter.

The pumps will deliver up to 6 m3/sec through two 1.4 m diameter high density polyethylene rising mains into the treatment plant.

Connections into the existing network built under urban central Auckland will be made via 16 cascade drop shafts that are between 25 and 70 m deep, ranging in diameter from 3 to 12 m.

Land for the shafts – which has already been designated to parks – is owned by Watercare, or its parent organisation Auckland Council.

An option exists to dispose of tunnel spoil at a landfill operation managed by Watercare.

Construction is anticipated to begin in 2019 and to be completed by 2025.

For more information visit the Watercare website.

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