TimCuff-TePaHarakekeOpens50-copy

Project Info

Client: Nelson City Council
Collaborators: Nelmac, Stantec, Department of Conservation

Stormwater Project of the Year

Awarded to Taylors Contracting by Water New Zealand, Stormwater Conference & Expo 2024

Project Description

Taylors Contracting’s Nelson Civil Department Manager Robbie Swarbrick discusses the project’s key challenges and the creative solutions that the Taylors team devised to overcome them.

Sludge solution
“The main environmental difficulty with this project was dealing with the residue of toxic sludge. Copper sulphate had been used over many years to treat the water to keep it clean; however as this became environmentally unacceptable the practice was stopped and the pond was overrun with Ruppia, aquatic weed and algae resulting in a smelly, stinky, pungent pond that was an eyesore.
“There was no design instruction provided to us for the disposal of the toxic sludge which remained at the bottom of the pond. Nelson City Council’s environmental policy of “reduce, reuse, recycle” prohibited the sludge being removed from site and disposed of at landfill.

Fish and wildlife management
“We worked alongside a fish and wildlife ecologist during the draining of the pond. Three-millimetre fish screens previously used at the Waimea Dam site were used to prevent the eggs of invasive species escaping the pond into the estuary.
“It took two days to fish the pond and sort the species, with thousands of eels transferred to new habitats. The Department of Conservation was on hand to provide euthanasia treatments for the invasive species. Records of relocated species were kept and Stantec Engineers recorded water samples hourly while the fishing process was undertaken.

“We came up with the solution of laying locally sourced Lee Valley Limestone “bricks” over the sludge layer. This essentially soaked up the sludge and provided a solid base layer for the subsequent layers of fill.
“This also solved the issue of the unpleasant odour which became prevalent after the draining of the pond and which had led to complaints from the community. This solution was also cost-effective and enabled the Nelson City Council to comply with the “no concrete” design brief which local Iwi had requested in order to return the area to a habitat as close to its original form as possible.

Sand to meet specifications
The weather played a part in the project, including providing an unexpected benefit.
“When we couldn’t get the supply of sand needed to meet design specifications within the allowed budget, onsite managers and council representatives came up with the solution to excavate the sand which had accumulated from a storm surge in the Tāhunanui back beach carpark. This was a real win:win – providing free maintenance on council reserves and reducing the cartage of sand which was readily and freely available locally.”

The name Te Pā Harakeke was gifted by local iwi and is resonant with meaning as harakeke (flax) grows in whānau lots sheltering the young growth at thecentre. The whānau of harakeke is stronger together and the name signals that the area will be a place for whānau.

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Before

Branch River Infiltration Gallery

Dam-Concrete

Waimea Community Dam

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Challies Island Bridge

Taylors Contracting Co. Ltd