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West Coast landfill erosion - Expert Reaction

Following heavy rainfall and flooding on the West Coast, the Fox Glacier landfill became exposed through erosion, with rubbish spilling out into the environment.

Associate Minister for the Environment Eugenie Sage has said she will investigatea number of old landfills around the country for such vulnerabilities.

The SMC asked experts to comment on landfills generally and this situation.

Dr Joshu Mountjoy, Programme Leader Marine Geological Processes, NIWA, comments:

"The rubbish that has been eroded from the Fox River landfill has become part of the sediment load of the river and transported to the coast. Reports show it has been dispersed widely along the coast and it is also almost certain that there will be a large hidden component of the waste that has been transported offshore and out of sight beneath the ocean.

"Directly offshore Fox River, the Cook Canyon comes to within at least 4 km of the shoreline and is a major pathway for transporting sediment from rivers to the deep ocean. The end of the canyon has not been found but is deeper than 4000m. We know from recent studies that sediment from rivers is actively being moved into canyons on the West Coast and it is likely that a component of the Fox River landfill waste will end up in the deep ocean by the same processes.

"A recent study on canyons offshore Sicily, published in the journal Scientific Reports, found huge amounts of rubbish in water depths up to 1000m transported there in response to flash flooding. We need to do a lot more to understand if rubbish is being transported into the Cook Canyon or other canyons around New Zealand but, as canyons are key marine ecosystems hosting some of the most concentrated biomass on earth and supporting important fisheries, it is something we definitely need to know about."

No conflict of interest.

Dr Jeff Seadon, Senior Lecturer, Build Environment Engineering, AUT, comments:

How hard will this situation be to clean up and what are the impacts of this rubbish in the environment, including in the ocean?

"Once waste gets into the environment it is very hard to clean it up and its effects can last for generations. When it gets into the oceans, currents can carry it thousands of kilometres from its origin as we have seen with plastics in the marine environment. By the time it gets back to shore, beachcombing is really the only way to clean it up. These wastes can be hazardous, so cleaning them up requires specialised knowledge and equipment to avoid injury or adverse health effects.

"However, plastics are just a small portion of the waste, though a very visible one. Hazardous waste from household and industrial chemicals like paint, garden pesticides, pharmaceuticals, personal care products, waste oil, batteries and treated timber can leach into surrounding soils, waterways, groundwater and the ocean. Those wastes can poison plants and animals, or be absorbed and passed up the food chain to come back to us in a more concentrated form."

How many landfills might be in vulnerable positions, are we doing enough to make sure they're sealed and safe from this kind of event?

"Modern landfills in New Zealand are world class. They capture a high percentage of methane emissions and have liners that ensure leachate containing hazardous waste is not able to pass into the environment. They are sited away from coastlines and waterways to ensure minimal damage in storms and other natural hazards events.

"However, in the past, landfills could best be described as dumps. There was no liner, no methane collection and no proper cover, which allowed water to pass through creating more leachate that spilled into the environment. In addition, they were often located by the seaside or near waterways. Filling in a bay to eventually provide parks or a valley to get the waste out of sight was a common approach. There are an unknown number of these around New Zealand and possibly tens of thousands of farm dumps where farm waste was dumped in a valley and covered over. This allowed hazardous waste to get into groundwater or trickle into nearby streams.

"Storm events, like the recent one at Fox Glacier on the West Coast, can uncover these dumps and the waste then flows away, often to the nearest marine environment. From there it can be carried out to sea or along the coast to wash up wherever the currents carry it.

"While some dumps have been remediated, it comes at a high financial cost. When you multiply that price across New Zealand, the cheap solutions of decades ago have come back to cost us greatly to fix the problem."

How can we better divert waste from the landfill?

"If we do not make waste in the first place, then we do not need to deal with the consequences. Our two largest waste streams are construction and demolition, and organics. Together these make up about two-thirds of our landfilled waste and it is costing the consumer dearly.

"For example, in houses, if you take into account the cost of the materials, the time wasted on site and the cost of disposal, this amounts to almost a quarter of the cost of the build. At the end of life, taking the building apart rather than demolishing it, can recover upwards of 80 per cent of the materials for recycling. This saves on virgin material and landfill space and helps to move to a circular economy.

"In New Zealand, we waste about $1.17 billion each year on food that is thrown out. If we think before we buy, much of this waste could be saved. It will also save on leachate production at landfills which then has to be managed, creating more cost.

"At the other end of the scale, much interest has been shown in plastics, particularly single-use plastic bags. These bags became very visible when washed up on West Coast shorelines after the landfill was washed away. While landfilled plastic bags represent just over 6,000 of the 3.5 million tonnes of waste disposed to landfill each year and much more to other classes of disposal site, their environmental impact worldwide has been the focus of many reports over the last few years, particularly on the marine environment.

"Alternatives to disposal for plastic bags do exist, like being used to make lightweight concrete, manufacturing fenceposts to replace the treated timber ones and mixed in asphalt for roads to increase the life and performance of roads. Currently, these are being worked on to see their applicability for New Zealand’s conditions. For the concrete and fenceposts, the question still remains – what do you do when the building or post finishes its useful life?"

No conflict of interest.


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