Collaboration between the NSW EPA, groundwater treatment plant proponents, licensees and water treatment practitioners has produced outstanding improvements in the water quality discharged from infrastructure projects.
Around a decade ago, Sydney was about to embark on many tunnelling projects associated with motorways and rail lines. These projects were expected to intercept areas with contaminated groundwater – a legacy of previous industrial activities that led to groundwater often containing toxic concentrations of pollutants such as ammonia, heavy metals, petroleum hydrocarbons and PFAS.
The NSW EPA is NSW’s primary environmental regulator and takes an environmental stewardship approach to its role. The NSW EPA also plays an important role during planning approval processes providing expert input to NSW planning authorities.
During its review of these proposals, the EPA’s technical experts recognised the need for a high standard of groundwater treatment and an opportunity to encourage the use of contemporary technology to protect and restore Sydney’s waterways. Without it, the construction and ongoing operation of this infrastructure could impact the sensitive receiving waterways around Sydney for many years to come.
The EPA proactively engaged with proponents, licensees and practitioners on the technical, policy and legislative framework for assessing and managing water pollution in NSW, in particular ensuring that modern treatment technology available in the market was properly considered for treatment of contaminants and mitigation of potential impacts.
EPA technical experts regularly scan for new treatment techniques and consider how these might be applied under different circumstances. Collaboration between the EPA’s technical experts and its Regulatory Operations division ensured this information was available to these stakeholders when they needed it, in a form they could easily interpret. Providing clarity regarding the EPA’s regulatory requirements, including licensing practices and principles, involved clear and consistent communication and utilised resources such as discharge impact assessment guidance available on the EPA’s website.
NSW EPA Senior Technical Adviser Nicole Jones said the key was ensuring the EPA was enabling stakeholders to identify the matters the EPA must consider when exercising its licensing functions.
“We need to consider a range of matters, including the pollution that will be caused, the environmental values of the receiving waterway and the practical measures that could be taken to avoid and minimise pollution and protect the environment from harm,” she said.
As a result, industry was enabled to better understand the potential risks and improve their impact assessments of the discharge after various options for treatment were considered.
“This information is now wrapped up into a robust discharge impact assessment that the proponent prepares as part of the planning submission or licence application,” Jones said.
“It’s not a one-size-fits-all approach. The discharge limits for the groundwater treatment plants are derived based on case and site-specific circumstances.”
Designing plants to treat contaminated groundwater to prevent or minimise harm and protect and restore the environmental values of waterways challenged licensees to translate the results of their impact assessment into practical measures for treatment of contaminants.
“Armed with their enhanced understanding of the technical, policy and legislative framework, industry has adopted increasingly sophisticated technologies capable of producing high quality effluent that presents a low risk of harm to waterways when discharged,” Jones said.
Individual site characteristics and limitations with some technologies meant that key licensing principles such as ‘avoiding and minimising water pollution’ and the concept of a ‘reasonable level of environmental performance’ were frequently central to licence negotiations.
EPA Technical Lead on Water Anthony Pik said the bar has been raised on what is considered a reasonable level of performance.
“It is now standard practice for groundwater treatment plant designs to include targeted treatments such as breakpoint chlorination and ion exchange as well as basic solids removal. Only 15 years ago basic solids removal and pH adjustment were generally considered adequate in these circumstances,” he said.
Proponents, licensees and practitioners are now proactively identifying potential pollutants of concern, proposing appropriate treatment technologies, and assessing the potential impact of any pollutants that remain at levels that can cause harm in a discharge following treatment. “This has meant that there are fewer pollutants requiring regulation,” Pik said.
Using the information in the discharge impact assessments and subsequent negotiations, the EPA has been able to establish robust discharge concentration limits for most pollutants of concern. However, there can be uncertainty in the influent quality and performance of the technology in some circumstances.
“To manage this, the EPA can use interim limits with a program of monitoring and reporting as a practical way to deal with the uncertainty of treatment performance while treatment plants were optimised and final limits negotiated,” Jones said.
Some pollutants that remain in the effluent following optimisation can prove difficult to manage. In these cases, the EPA used pollution reduction programs that fostered innovative approaches to treatment. This included technical investigations into treatment options with the EPA following up with field visits and meetings with licenses, consultants and practitioners.
The treatment plants used to treat contaminated groundwater intercepted by infrastructure projects continue to evolve and improve. Some of the construction treatment plants that came online in 2023 have generated sufficient data to robustly evaluate their performance.
In most cases, the plants were found to be producing better quality effluent than anticipated in their discharge impact assessment.
“It became evident during the review process that data on influent and effluent quality was essential to facilitate an informed evaluation of plant performance,” Jones said.
“Working with the licensees to source influent data meant that variations in influent quality were accounted for in the assessment of plant performance.”
Engagement with proponents, licensees and water treatment practitioners has matured to the point where industry is now well enabled to meet EPA regulatory requirements to adequately understand the risks posed by contaminated groundwater. This is reflected in their increased capacity to design and operate treatment plants that protect and restore waterways.
“The vast majority of pollutants in groundwater intercepted by tunnelling projects are now treated to levels that don’t cause harm, and water quality objectives are being restored or maintained in Sydney’s waterways,” Jones said.
“It is a significant outcome for waterway health and the community more broadly in Sydney.”