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Smart solutions – Contaminated land

Urban growth is putting pressure on councils to clean up contaminated land. Current regulations are not quite tailored for the job and can be open to interpretation. So, is it time for a nationally-led more consistent approach? Patricia Moore has been digging the dirt.

Andrew Hart, Golder Associates.

Our country has an estimated 20,000 contaminated land sites. They’re a legacy of decades of usage, storage and disposal of hazardous substances by industry, agriculture and horticulture. However, we don’t have the long history of heavy industrial and manufacturing activities that tends to result in gross contamination.

That’s according to Andrew Hart, associate and senior environmental scientist at Golder Associates (NZ). “As such,” he says, “the majority of contamination is present in shallow soils that result in a conflict with pressure for urban development.”

Regional councils and territorial authorities have inherited the problem. There used to be marked differences between how different councils handled the remediation of contaminated land.

In January 2012, the National Environmental Standard (NES) for Assessing and Managing Contaminants in Soil to Protect Human Health Regulations 2011 came into effect. This led councils to take a more standardised approach.

Sarah Schiess, Tonkin + Taylor.

But, inconsistencies still exist, says Andrew. “In part, that’s because the NES is a planning document, rather than a clear, robust framework for the management of contaminated land risks.”

Sarah Schiess, senior consultant, Tonkin + Taylor, also notes variables in the interpretation. “Additionally, the NES is dealt with by territorial authorities and only considers human health,” she says. “It does not deal with discharges from contaminated land that could affect other environmental receptors.

“Discharges are dealt with by regional councils and governed by rules in regional plans which may differ considerably across the country.”

Affordability comes in to it too, says Andrew, with larger urban councils better able to employ dedicated technical staff than small, rural councils.

Sarah makes a similar point. “It seems counterproductive,” she says, “that each territorial authority is responsible for technically understanding and applying the NES while discharges from contaminated land are considered separately by others. It would seem that a case should be made for a nationally-led, consistent approach.”


Natalie Webster, Pattle Delamore.

Some 20,000 sites sounds like a lot for a country of our size, but how significant is it? Natalie Webster is technical director, contaminated land at Pattle Delamore Partners. She says that while there are a large number of land-use types with the potential to cause ground contamination – as defined by the Hazardous Activities and Industries List (HAIL) – there is only a sub-set of sites where actual contamination impacts are present.

There is a smaller number again where existing contamination is of sufficient magnitude that risks to human health and / or the environment exist.

Andrew Walker, GHD team leader, environment – contaminated land, says he has worked on overseas sites where problems dwarf what we might consider significant.

“That’s not to say we don’t have our proportional share of contaminated land including legacy mines, fertiliser production, gas works, and oil and gas sites,” he says.

“But these typically haven’t gained widespread public attention and are generally only on a local scale.”

He adds that where contamination is present at a site, this is usually a result of poor practices and / or established process management.

He adds it’s important to keep in mind that we previously “didn’t know any better and it was commonplace to simply dispose of chemicals in the ground”.


So, what’s the solution? Sarah says there have been huge advances in the application of in-situ remedial solutions for groundwater contamination.

“For example, enhanced in-situ biodegradation of petroleum hydrocarbons and chlorinated solvents is a standard approach that is extremely cost-effective and regularly used in locations such as Australia and the US.

“New Zealand seems to be lagging in the uptake of this and other in-situ remedial technologies.”

Andrew Walker, GHD.

Andrew Walker also sees the promotion of in-situ remediation technologies – sustainable remediation – as a solution.

“At a local and regional government level, this is a massive challenge as, almost 99 percent of the time, the economics point towards physical excavation and landfill.

“The conservative approach, currently adopted to contaminated land risk assessment, is resulting in large volumes of soil, which may not have presented an immediate risk, being unnecessarily disposed
to landfill.

“Using secure locations – landfills – for disposal is simply stockpiling known and unknown issues for future generations to deal with. Our landfills play a necessary function but are a precious resource which should be utilised wisely.”


As the demand for more housing increases, Natalie says the pressure is on councils to consent sites to allow for development. However, they need to ensure a robust amount of information on the risks from contamination is gathered, and that those risks are appropriately managed.

“Another challenge is that the NES requires consenting of HAIL sites where a ‘significant’ volume of soil will be disturbed or removed, even when contamination is not present at a concentration which poses a risk to human health,” she says.

“This is increasing the consenting burden for councils as well as landowners and developers.”

Natalie says ‘global’ consents, whereby multiple sites over a wide area are included under the same consent umbrella, are
a solution.

“Such consents are helpful because they allow work on large-scale developments to begin and then progress without consent-application related delays.”

But, she adds, this process requires a high degree of trust between the council and the developer. “A robust contamination assessment and reporting process is required to be written into the consent and undertaken in good faith by all parties.”

A key challenge, says Andrew Hart, is the limited scope of the NES; it is applicable only where one of the five activities it covers are proposed. “However, there are a number of sites with high-risk contamination that fall outside the NES and leave territorial local authorities with little ability to regulate and manage the risks.”

He says there’s also a limited framework to assess and manage new and emerging contaminants. “The recent focus on PFAS (per- and poly-fluoroalkyl substances) is an example. The primary risk is to human health, mainly through the consumption of contaminated media such as groundwater, but where the land continues to be used for the same activity, the NES is unlikely to be triggered.”

In Sarah’s opinion, the Resource Management Act led the world in legislating risk-based remediation of contaminated sites when it was introduced. However, she says, “sadly, New Zealand now seems to lag behind other countries, such as Australia and the US, in the active remediation of contaminated sites.”

Andrew Walker believes we’ve been dealing with contaminated land in the same way, for far too long.

“The book needs to be thrown out and we need to start lobbying for real, sustainable change from central government. Arguably the last election was won and lost on this issue so now’s the time to turn up the heat. After all, aren’t we in the contaminated land industry to make New Zealand a better place?”

• Patricia Moore is a freelance writer. mch@xtra.co.nz

This article was first published in the August 2018 issue of NZ Local Government Magazine.

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