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While the wheels are turning slowly on setting up a targeted dredging and clearing programme in the Mahurangi River, there are signs that a resource consent application could be lodged in the first half of next year.
The Mahurangi River Restoration Trust is spearheading the dredging project and has received $20,000 from the Rodney Local Board to clarify the scope of the work needed and its viability.
Currently, navigation of the river for most vessels is limited to about 2.5 hours either side of high tide. The proposal is to dredge about six kilometres of the worst affected sections of the river – between Dawson and Hepburn Creeks, and the Cement Works and the town basin – to create a 15-metre wide and at least 1.5 metre deep channel.
Trustee Peter Thompson says the need for the dredging is becoming more urgent in terms of keeping the restored scow Jane Gifford in Warkworth.
At present, the vessel is restricted to exiting and entering Warkworth an hour-and-a-half to two hours either side of high tide. This is severely limiting what she can be used for and the funds that can be raised for her upkeep.
“We recently had her out of the river for survey and found damage along the bottom where she’d been sitting on the mud,” Peter says. “It wasn’t serious, but it’s not what you want to see. She belongs to the people of NZ and we have a responsibility to ensure she is operated properly.”
Engineering reports suggest that the river system receives about 100,000 tonnes of sediment every year, from a catchment that covers roughly 113 square kilometres.
It’s anticipated that, initially, more than 87,000 cubic metres of spoil will need to be removed.
Peter says tests have shown that the content of the spoil is benign and the plan is to dispose of it on low-lying land, out of the Coastal Management Area.
“Rather than treating it as a waste product, it will be used as a resource,” he says.
“The river bed is littered with everything from fallen trees and logs to engine blocks and truck tyres so removing these will also form part of the project.”
Peter acknowledges that there are numerous Regional and District Plan consents required for any dredging and disposal works, which require a carefully planned approach. But he is eager to get the work started.
“The longer we leave it, the harder it will be. I’d like to think this project will become a template for other towns in NZ who want to restore and maintain their rivers.”
The trust also faces the fact large scale dredging and the related requirements for enduring maintenance are not currently considered to be a core function of Auckland Council and, therefore, is unlikely to attract significant funding.
Peter says it’s thanks to the generosity of companies such as Buckton Consulting Surveyors, Hutchinson Consulting Engineers and O’Connor Planning, the Rodney Local Board, Council staff and the ongoing support of members of the community, that the project has been able to progress.
“Once we have the consents we need, we will have to apply to funding agencies for grants to carry out the work.”
Meanwhile, Peter has recently returned from the Netherlands where he completed a six-day UNESCO-endorsed seminar on dredging. Participants attended from all over the world and were addressed on best practice by world leaders in the field. “It was a fascinating week that confirmed in my mind that the methodology that we are using here is 100 per cent on track in terms of the environment. What we’re doing fits right within the ethos of modern dredging practices.”
