Debris control structure proposal abandoned
The Whakatāne District Council’s Projects and Services Committee has adopted a resolution to abandon a planned debris detention structure in the Awatarariki Stream catchment above Matatā.
At its meeting on July 4, the committee received a 117-page review report on the proposed structure, which was one of the key regeneration projects developed to prevent a recurrence of the debris flow and flooding disaster which struck the township in May 2005. The review process was initiated by the Council in March and was led by highly-experienced local government consultant and engineer Alan Bickers.
Committee Chairperson Councillor Christine Chambers says that after considering the report, Councillors made a unanimous decision to take no further action to develop debris detention solutions for the Awatarariki catchment, upstream of the escarpment immediately behind the town.
“The report reinforced the concerns raised by our consultants and independent advisors earlier this year about the cost and feasibility of the planned structure,” Councillor Chambers says. “We remain committed to investigating whether there is a workable downstream solution and have resolved to re-evaluate three of the debris channelling options which were part of the original Awatarariki investigation, plus an additional possibility of constructing a debris detention basin.”
The committee has asked the recently-formed Matatā Projects Governance Group to report back to the Council by August 1 on the work required to re-evaluate the downstream options to control debris flows from the stream and provide a project plan and timeline for the work.
Councillor Chambers says meetings were held with affected property owners in the Awatarariki debris fanhead zone earlier this week to provide information on the review report and its recommendations. “While there was understandable frustration at the time and cost which has gone into the debris control structure plan, the property owners solidly supported the decision to abandon what is clearly an unworkable proposal and move on with the effort to find a solution which offers the best possible outcomes for the community and the District,” she says. “We will continue to keep property owners and the wider Matatā community informed of developments as they arise.”
Amongst the significant findings highlighted by the “Bickers Report” was that in its efforts to provide certainty for the Matatā community in the aftermath of the disaster, insufficient attention was given to where the responsibility for action lay.
In 2008, community and cultural objections to the planned dam saw it replaced with a proposal for a flexible ring net structure which would offer partial debris containment in the upper catchment, with a downstream debris spillway to cope with any flow which reached the lower catchment. Detailed design work proceeded, but a peer review in 2010 resulted in the project scope being changed to full containment (of a 250,000 cubic metre debris flow) in the upper catchment. The engineering complexity of a ring net structure on such an unprecedented scale, together with the difficulties associated with anchoring the structure adequately, saw the estimated cost of the project soar from $2.4 million in 2008 to $5.8 million by 2011.
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