River threat to old landfill Closed down landfill sites
The Timaru District Council will borrow about $500,000 for urgent stop gap work to reduce the chances of waste from a closed landfill being swept into the Rangitata River.
Council’s acting climate and sustainability manager Vincie Billante told councillors on Tuesday that the work at the Peel Forest landfill needed to begin as soon as possible and urged them to be ‘‘proactive, rather than reactive’’ while warning that other landfills in the district faced similar issues.
The landfill, at the end of Dennistoun Rd atop a gully adjacent to the Rangitata River, was operated from the 1960s until it was decommissioned in 2004, and has posed a risk for leaching since the December 2019 flood in the Rangitata River.
That flood, according to a TDC report, caused erosion at the toe of the terrace resulting in the failure of the cliff face, exposing superficial rubbish and debris within 0.5-metres of the surface.
‘‘Flooding is becoming more frequent, we recommend you look at this issue critically,’’ Billante told council’s infrastructure committee meeting.
‘‘We have advocated for the minimum works, and then look at the bigger issue. This is not unique to Timaru.’’
Billante’s report, compiled with group manager for infrastructure Andrew Dixon, recommended the commencement of river engineering works to redirect the southern most Rangitata River channel away from the bank and forming a vegetated buffer at the base of the terrace alongside recapping the landfill.
The council voted in favour of this work (option two of five presented), which will cost about $500,000, with the unbudgeted works being funded by a loan. However, the work came with a warning that ‘‘this option will only be effective for relatively small scale flood events, not major catastrophic ones. This addresses the immediate needs to mitigate potential flooding from the Rangitata River and further erosion of the cliff face and terrace of the gully where the landfill is located’’.
Council’s report revealed that specialist consultants were commissioned to investigate various options which were estimated to cost from $500,000 to $5 million ‘‘which indicates the complexity in the work required for each option’’.
‘‘I will say it [the work] will happen in this financial year, ideally we would like to get it done during the summer months,’’ Billante said.
Dixon told councillors it would only take a flood of reasonable significance to cause erosion of the landfill and lead to waste getting out.
The report noted the Fox River landfill breach, in which thousands of kilograms of waste spewed from the dump on the South Island’s West Coast, as reminder of the need for stronger monitoring of landfills.
‘‘Flooding is becoming more frequent, we recommend you look at this issue critically.’’ Vincie Billante
Council’s acting climate and sustainability manager
Billante said the Peel Forest issue related to not just the one landfill, but to many of the 36 closed landfills under council jurisdiction within the Timaru district.
‘‘Many of these are adjacent to waterways, but level of risk of these landfills being eroded and waste being exposed and entering these waterways is not known,’’ the report said.
Billante suggested the council needed to create a landfill management
plan to address concerns about potential leaching.
Timaru District Mayor Nigel Bowen said after the meeting that the council was particularly concerned about the Peel Forest landfill site.
‘‘All landfills will need to be addressed on a case by case basis, not all will have the complexities of being so close to a natural hazard such as the river,’’ Bowen said.
‘‘Council are closely monitoring both current risks and have an approach to both understanding the full extent of any potential problem, and addressing both the current and longer term needs that may come through.
‘‘The Peel Forest landfill is a great example of monitoring the site over time and dealing with any issue as they have come to light.’’
Bowen said a longer term view of mitigation and adaption of all closed landfills through a long term management plan will be considered in the next Long Term Plan.