1. Getting started
Start by gathering as much existing historical information about the uses of PFAS at your site. Include interviews with personnel (historical and current), inspections of site activities, reviews of chemical manifests, containment systems, waste systems, and assess the frequency and locations of PFAS product use or disposal. This desktop review should allow you to home in on the key areas of your site where PFAS may be most prevalent.
2. Building a preliminary picture
The next step is to build a preliminary picture by developing a conceptual site model. This identifies where PFAS from your site might be impacting a potential receptor such as nearby residents, animals or fish. Consider PFAS movement that could link sources and receptors through pathways, such as groundwater seepage, stormwater runoff and airborne movement of foam.
3. Narrowing the key areas and determining priorities
Having identified the main transport pathways for PFAS at your site, you can apply a targeted approach to sampling that could save cost and time compared to traditional, extensive sampling approaches. For example, if the key pathway is the surface water drainage system, samples could be taken at key features within the system to identify the mass of PFAS contamination emanating from different source areas. Then, the results can be grouped and ranked into high-, medium- and low-priority tiers. This approach can rapidly expose higher-priority areas for immediate management. More intensive, extensive sampling can follow.
4. Identifying ‘quick wins’
Once the highest priority areas have been identified, it may be possible to identify some easily achievable maintenance and clean-up actions that could yield ‘quick wins’ at a relatively low cost – in other words, achieving significant improvements very quickly, with slower or longer-term mitigation actions to follow later. Some simple solutions – such as clearing sediment pits, cleaning drains and managing surface water – could even reduce PFAS concentrations by orders of magnitude. It is always encouraging to achieve some rapid results that build confidence and momentum.
5. Adding detail to the PFAS picture, both on and off site
A preliminary conceptual site model and some key wins are only the beginning of the story. Now is the time to delve more deeply to understand and close out potential risks. A detailed sampling and analytical program will be needed, but the key here is to start with the end in mind.
The preliminary conceptual site model demonstrates the basic pathways from sources to receptors, but the conceptual site model should be updated as new information and understanding of risk evolves over time. This helps you to communicate and focus the next stages of assessment with confidence and efficiency.
It’s one thing to gather data, but another thing to understand what it really means, and this is where complex data interpretation come in. There are techniques that can analyse the ‘fingerprint’ or ‘signature’ of the different PFAS samples, which can greatly improve the understanding of site sources, transport pathways and the fate of PFAS within the environment.
3D modelling that integrates geological, hydrological and hydraulic modelling with the conceptual site model provides advanced information and is a useful communication tool to translate complexity into a more intuitive form for regulators, non-technical decision-makers, and the broader community.
6. Assessing and communicating risk
As the information is gathered, the risks need to be assessed to determine the potential for adverse effects on receptors. The risk assessment process should aim to differentiate areas considered to pose low and acceptable risks (where further work may not be needed) from areas where risks are uncertain or considered likely to be unacceptable (where further action is required). For activities or areas where risks have been ranked as unacceptable, remedial action should be taken.
Another important management consideration is to communicate risks relating to health and the environment to stakeholders in a clear, timely, accurate and sensitive manner. Much of the information about PFAS is technical and complex, so adequate plain-language explanation and context will be needed to provide clarity and reassurance and avoid unnecessary anxiety.
7. Planning for action
So, you have identified risks which have been ranked as unacceptable, and action is required. It is now time to develop a clean-up plan, with a roadmap of milestones. However, in some circumstances, remediation of PFAS contamination may not be feasible, or further detailed assessment may be unlikely to add value. In these instances, practical solutions may include minimising or eliminating PFAS release and implementing management measures to limit exposure on and off a site.
The risk management strategy will inform the screening of various available remediation options from the perspectives of efficacy, cost-effectiveness, practicality and impacts on the community and environment. Many new, innovative technologies are showing promise in research trials or in pilot stages, so seek advice from remediation specialists who are abreast of these rapid developments in the quest for sustainable, cost-effective methods that can be deployed at the right scale for your site.
8. Cleaning up
It is worth considering whether some of the more traditional low-cost, low-technology remediation methods could deliver a pragmatic and cost-effective solution for your high-priority areas. Such approaches could include surface water diversion or containment, re-sealing of concrete or asphalt, and limited removal of surface soils. 3D modelling of source areas can reveal a ‘heat map’ to locate PFAS hot spots at depth and enables the volumes of soil that needed to be removed to be tested under different remediation scenarios. This helps to cost the remediation plan prior to breaking ground.
With a combination of highly targeted soil removal and some re-concreting and re-asphalting, it may even be possible to give your operational facility an extension of life.
9. Continuing on the right path
After you’ve dealt with your quick wins and your highest priority areas for remediation, you’ll need a targeted and strategic PFAS site management plan. The plan should monitor for changes in water quality following implementation of mitigation to validate improvements and track key sentinel locations to check that the risk profile remains low and acceptable.
Although there is still much to learn about the complexities of PFAS risks, management and remediation, no business can afford to be complacent. There are practical, rapid and cost-effective measures you can implement that will make big improvements to your liability and to the safety of your workers, your local community and the environment.
ABOUT THE AUTHORS
Rachael Wall is a Principal Chemical Engineer, based in Melbourne, Australia. She has over 18 years’ experience in the field of environmental assessment and groundwater remediation including a PhD in Chemical Engineering in wastewater treatment. Rachael is the technical lead for several complex operational sites under environmental audit where PFAS are key chemicals of interest. Her involvement in these projects covers steering the progression of the assessment and clean up strategy, client and regulatory liaison, environmental assessment, and groundwater remediation.
Jonathan Medd is a Technical Director and Principal at WSP, based in Melbourne, Australia. He has over 27 years' experience in research and environmental consultancy and is an EPA appointed Auditor for both Contaminated Land and Industrial facilities. He specialises in the use of risk-based methods to provide targeted outcomes and drive more sustainable solutions for regulatory closure of contaminated land, aquatic and groundwater environments. Jonathan is responsible for leading the Water Remediation technical capabilities for WSP in Australia.