The methodology changes allowing Bay of Plenty Regional Council to use a cutter suction dredge and pipeline to remove sediment directly from Kopeopeo Canal to goebags in containment sites has been given the green light with the consent variation approved earlier this month.
The original consent granted in November 2014, allowed the project to take a staged approach to remove, safely store and bioremediate up to 40,000m3 of sediment from the Canal using excavators and trucks to transport material between the Canal and each of the containment sites.
While the consent had a significant number of control measures, the community raised concerns associated with the methodology, including the potential for contaminated sediment to be spilled onto public roads and the associated risk of dust generating air quality effects. These concerns, along with changes in the availability of the alternative technology, led to the evaluation of the new extraction and transfer method to keep sediment fully contained during the process. The new method involves dredging the wet sediment, pumping it to the containment sites and using flocculation and geobags to safely contain the sediment. It is this alternative methodology that has been consented.
Project Manager, Brendon Love, outlined the most significant changes to the consent.
“There are a few new aspects to the consent as it provides complete containment during transfer to the containment sites so virtually eliminating the risk of dust being generated during that transfer process into the geobags at the containment sites. That is a great relief for many in the community who had concerns about how the previous transport method could be managed.
“There are also changes to aspects such as flood management and water quality monitoring. Because the containment sites have a primary containment system (geobags) and secondary containment system (a bunded, high-density polyethylene-lined area) there are no longer any potential effects on groundwater, but excess rainfall and stormwater that collects in the bunded area will be discharged back into the canal.
“A lot of the original conditions remain such as the Independent Monitor, Cultural Monitor, Compliance Officers providing independent oversight and the Community Liaison Group providing the communications link between the project and the community. The validation sampling and targets which measure the effectiveness of the remediation works and ensure the project objectives are met also stays the same. This is a significant milestone for the project and follows at least 12 months of laboratory studies, pilot trials, technical assessments, and community consultation,” Mr Love said.
A number of key documents sit behind the decision including a report from the independent commissioner who granted the consent and comment from the Independent Monitor to the project.
The consent was granted ‘non-notified’ and the report outlines why the Independent Commissioner thought that it was appropriate in the circumstances. The consent would need to be publically notified if “the proposed new methodology increases by more than a minor degree the scale or intensity of adverse effects that were anticipated to arise from the existing consented methodology”. Considering a range of matters including water quality, noise, dust, groundwater, flooding, and traffic, the Commissioner concluded that “…most if not all of categories of potential adverse effect listed…. the scale or intensity of adverse effects will be reduced by the proposed new methodology”.
The granting of the consent variation is a significant milestone for the project. The project is also working closely with a preferred remediation contractor to get a contract in place for physical works to commence.
“It has been an eventful few weeks as we have our consent approved, contractual discussions with the preferred remediation contractor to carry out the works, and additional funding approved. We look forward to commencing dredging in the new year,” Mr Love said.