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Eastmans Low Flow Channel, Halswell Downs Wetland and Milns Basin

Hoon Hay, Christchurch

January 2021 - Current

Christchurch City Council

Overview

The Eastmans Low Flow Channel and Halswell Downs Stormwater Wetlands are located within a cluster of CCC owned properties east of Halswell and form part of the wider Eastman Wetland facility, which aims to reduce flooding in the Heathcote River. 

The Low Flow Channel is approximately 650 meters long and will convey the water from Hoon Hay Basin and Sutherlands Basin (Hoon Hay Valley Catchment) into the Eastman Outlet Channel (formerly known as Milns Drain). 

Halswell Downs Wetland is required to treat attenuated stormwater runoff from the adjacent Halswell Downs subdivision. The wetland will be bunded along its south-eastern side by an isolation bund. 

Eastmans Low Flow Channel

Project Scope

Eastmans Low Flow Channel works includes: 

  • Site establishment 

  • Site clearance, including removal and disposal of existing vegetation, stormwater structures, fences

  • Setout and survey of works 

  • Excavation of approximately 3000 cubic metres to form the channel to form the channels 

  • Tie-ins to existing waterways, including ecological oversight 

  • Formation of maintenance and access tracks on either side of the channel

  • Surfacing of the maintenance tracks and access tracks 

  • Grass establishment and planting along the newly formed waterway.

 

Halswell Downs Wetland: 

  • An earth bund constructed from a combination imported gravel fill and site won material 

  • Permanent diversion of an existing drain into the Wetland and reconnection with the existing drain downstream of the bund 

  • Installation of culverts 

  • Installation of inlet and outlet connections 

  • Cut to fill/raise sections to create island, mid-pond, forebay and outlet ponds 

  • Installation of a gravel access track around the wetland 

  • A combination of native planting and grass for the wetland and drain banks, bund and the earthworks areas. 

Take a look:

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