$17m sewerage upgrade

18:50, Feb 05 2013
Bruce Oliver
Big project: Marlborough District Council project engineer Bruce Oliver visits the sewage treatment plant where work has started on a $17 million upgrade.

Work has started on a $17 million upgrade of the Blenheim sewage treatment plant and should be finished by the end of the year.

Council assets and services manager Mark Wheeler said treated domestic sewage effluent would no longer be discharged into the Opawa River near the end of Hardings Rd.

Instead it would be filtered through wetlands then piped into the Wairau River estuary to be washed out to sea with the outgoing tide.

Auckland-based HEB Construction started earthworks at the site on January 7, after placing a successful tender for $12.2m worth of the work.

Council project engineer Bruce Oliver said HEB recently completed a similar but larger sewage treatment project north of Christchurch.

Mr Wheeler said the new scheme added domestic effluent to industrial waste already pumped into the Wairau Estuary.


The HEB contract also involved building eight shallow treatment ponds covering 25 hectares and an irrigation scheme to spray effluent over pastured areas of the site.

Planning and development engineer Stuart Donaldson said the upgrade was needed to improve water quality in the Opawa River which contained unacceptably high levels of faecal bacteria below the sewage outlet. "This was a human risk," he said.

The Opawa was tidal for 3.2 kilometres from the sea, causing discharged sewage and algae to wash down the river, then back, Mr Donaldson said. Also, the 100 litres a second of waste discharged was a large amount compared with the river's 1900-litre-a-second flow.

Mr Oliver said preliminary work had been done, improving drainage channels and planting the perimeter of the site in naturally occurring native species.

When the main project was finished, the council would build a walking track from a new car park in Hardings Rd to the beginning of a Department of Conservation track leading to the wreck of the Waverly, he said.

Mr Wheeler said the council started consulting with Hardings Rd residents in 2007 and was also working closely with Rangitane, Ngati Rarua and Ngati Toa iwi.

The project is being paid for by ratepayers plus $5m of infrastructure upgrade reserve funding from Marlborough District Council Holdings.

The Marlborough Express