PFAS compounds are designed to be slippery. They keep food from sticking to non-stick frying pans, help rain slide off breathable outerwear, and ensure mechanical parts move smoothly.
So, it is not surprising that they can also be “slippery” to measure. It can be even more difficult to demonstrate the absence of PFAS — situations where they aren’t present at levels to show cause for concern.
But Per- and Polyfluoroalkyl Substances, collectively known as PFAS, have been identified as carcinogenic, and a threat to human health and the natural environment. This means that property owners, environmental regulators, political leaders, and the general public are increasingly concerned about locations where PFAS compounds may be present and potentially impacting groundwater and surface water.
A California landfill shows the pervasive nature of PFAS
The story of investigating just one property in southern California – a redeveloped landfill – can help explain some of the complexities involved in PFAS investigations.
This story starts when a California regulatory agency, the State Water Resources Control Board (SWRCB), wanted to get a better understanding of PFAS contamination in the state. They sent directives to the owners of both currently operating landfills and properties that contained closed landfills, instructing them to investigate those properties for PFAS impacts. This would include collecting and testing groundwater and leachate samples for constituents of concern.
Our client for this project is currently performing remediation of the landfill. Current standards for landfills, which include an impervious underlying layer, were not in place when the landfilling occurred, since the landfill predates them. There was also no system for treating the leachate — precipitation that flowed through the landfill, possibly picking up harmful chemicals along the way.
Because PFAS compounds have been used in such a wide range of materials, including paint and other construction materials, there was potential for PFAS-impacted leachate to flow into groundwater on site. The question was: How to measure local PFAS impacts in a way that meets the regulatory agency’s requirements?
Why are PFAS so difficult to measure?
For a variety of reasons, PFAS are extraordinarily slippery when it comes to measurement. One reason is that regulations stipulate that they be measured to extremely low concentrations – in the parts per trillion range – and it’s only recently that testing equipment has been able to give reliable results at those levels.
Another reason PFAS are hard to measure is that they are literally everywhere. Over the past 50 years, PFAS have been used in so many formulations and so many products, that it’s hard to determine which readings come from the site and which are background – blown in by the wind, for example.
A third reason also comes from that “PFAS everywhere” aspect. The ubiquity of PFAS compounds makes it challenging to avoid cross-contamination – so much so that an investigating team might inadvertently bring PFAS on site. There can be PFAS on footwear, clothing (particularly breathable outerwear), lunch wrappings, gloves, and other everyday items. The “forbidden” list included in an investigative work plan can be daunting. For example, one of our team members covered the seat cushions in his truck to avoid potential contamination from any stain-proofing treatment used on the seat covers.
To overcome these challenges, our teams have developed standard procedures and sampling work plans that consider the need to avoid contamination of groundwater samples gathered from the site.
One of our special challenges on this job came from the depth we had to reach, in order to pull groundwater samples from the deepest parts of the former gravel pit – between 260 and 280 feet below grade.
Drilling boreholes that deep was not a problem but sourcing the downhole pumps we needed to place at depth, to bring the groundwater to the surface, was difficult. It is challenging enough to get pumps able to draw from those depths, but to get them without components containing PFAS was even more difficult. There simply isn’t yet a ready supply of equipment free of PFAS, although this situation is changing rapidly as manufacturers scramble to meet this growing need.
Our staff worked with several vendors and manufacturers of PFAS-free sampling equipment and narrowed down the choice of the sampling device to one that is non-purging, PFAS-free and capable of being deployed at the depths required.
On this project we were fortunate to work with a client who took their responsibilities seriously, understood the procedures we had to follow, and invested in a comprehensive job of testing. We tested thoroughly and determined that the site met California standards for PFAS, while adhering to strict field quality control and assurance procedures. The SWRCB was satisfied with the field program and deemed the data collected as part of the program as being representative of the site, and no further investigation of PFAS was requested at the site.
* This work was performed by Golder professionals who joined WSP in an acquisition completed in 2021.
