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The length of the channel was 170m and it was approx. 7m wide at the top once the widening work had been completed. The subgrade was stabilised with 8% lime, the main armour boulders were 300mm placed in a 600mm layer and the riprap at the drop structures were 750-900mm in diameter. The channel then had a void fill placed over the top to remove any voids.

This was a staged project with 3 separable portions. Each separable portion required a high level of attention to both environmental and stakeholder management. The works involved working within several established residential properties. Given the risk to floods and subsequent erosion and sediment transfer along the drain a detailed methodology and environmental management plan were prepared. Clean water flowing over completed water was pimped over the work area to prevent the contamination.

Prior to any forecast wet weather the current work area was covered with temporary clean material. The project was successfully completed ahead of schedule and without environmental incidents.

This was an invited tender 3 waters panel CCC panel project, requiring a high level of attention to detail with respect to Environmental Management and earthworks within the waterway.


March 2021 – Sept 2022


Christchurch City Council 





This project involved upgrading the existing narrow drain in the Heathcote Valley to improve the stormwater flood capacity of an existing drain. The work involved removing existing vegetation, excavation of the channel to increase the channel width, stabilisation of the subgrade followed by the refilling of the channel with specifically graded boulders and riprap rock.

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