PFAS Testing of Groundwater Samplers: Q&A with Wes McCall, Geoprobe® geologist
Wes, before we get into the tech stuff, tell us where you have been hiding out during the COVID shutdown, we haven’t seen you around the office.
Yes, the last couple of months have been pretty unusual. Most of the time I have been working from home providing tech support for clients and working on a couple ASTM standards and new technical bulletins. However, I did spend a few days at the Direct Image® Training Center working on some projects.
It sounds like you have been keeping busy, even while isolated, and we hear you have been working with the PFAS compounds. What’s up?
The PFAS compounds have really “emerged” as a significant contaminant of concern all across the nation. These polyfluorinated alkyl substances have been used in many industrial and commercial products and applications. Unfortunately, this means they have contaminated the soil and groundwater at many locations. Because of the very strong bonds between the fluorine and carbon atoms in these compounds, they are nearly indestructible (persistent) and their high solubility allows them to readily migrate in groundwater.
We have been supplying groundwater sampling products for decades. Why do we have to do PFAS testing on these systems now?
Good question … The U.S. EPA and many state regulatory agencies have established health advisory levels, or action levels, for PFAS compounds that are at or below 70 parts per trillion. Yes, 70 parts per trillion or 70ng/l for drinking water. Currently labs are using analytical methods (LC/MS/MS) that can detect many PFAS compounds at the 2ppt to 5ppt levels, this is about 1000 X below levels we have been concerned with before for environmental sampling. These very low action levels and detection levels combined with the widespread use of PFAS compounds in many commercial products means there are significant concerns with potential cross contamination of samples. To give an example, there were concerns that anything with a Teflon® component or containing Teflon® tape or sealants may cause detectable PFAS cross contamination. Also, anything coated to be water or oil resistant (e.g. your water proof rain coat, the carpet in your house, the wrapper on the burger you had for lunch, the pizza box) probably contains detectable PFAS compounds (see Denly et al. 2019 and Rodowa et al. 2020).
Running the 175GWP onsite during a field study with Susom Dutta, Geoprobe® 2019 summer intern. Susom was working on his Ph.D. and this field project became a significant part of his dissertation. He successfully defended his dissertation this spring at the University of Massechussetts-Lowell. We used the 175GWP to collect groundwater samples at multiple depths and then Susom conducted field screening for hexavalent chromium with a new miniature anode stripping voltametry (ASV) device onsite.
So, what are the systems you have been testing and what do your results indicate?
In this round of testing we have focused on groundwater sampling tools and systems used during many groundwater investigations. This includes the Hydraulic Profiling Tool (HPT) system, the new 175GWP groundwater profiling system, the Screenpoint16 (SP16) and Screenpoint22 (SP22) groundwater samplers, and the prepacked screens used in many direct push installed monitoring wells. We set up on the bench and conducted rinsate tests with PFAS free water of all the system components that would be used in the field. I have to say I was a bit surprised that all of the systems tested were found to be nondetect for each of the 36 PFAS compounds on the Wisconsin PFAS analyte list. We worked with Jim Occhialini at Alpha Labs in Westborough, Massachusetts, for the analytical work.
That sounds like pretty good news. How can users of Geoprobe® products obtain this data?
We have developed PFAS Technical Bulletins for each of the groundwater sampling/investigation tool systems we have tested. The bulletins provide a detailed review of the equipment tested and procedures used. In addition, the lab report from Alpha Labs is included with each bulletin. These bulletins can be downloaded from our website at these links:
- Hydraulic Profiling Tool (HPT)
- 175GWP (groundwater profiler)
- SP16 & SP22 groundwater samplers
- Prepack well screens
One last question; if you were going to the field to perform direct push groundwater sampling for PFAS compounds, what basic steps would you take and what groundwater sampling system would you use?
First, be sure you are familiar with the site specific PFAS work and sampling requirements. Which state you are working in and which agency the work is being done for will influence your site-specific requirements. There are lots of different guidance documents for the appropriate personal protective equipment, sampling materials, and even personal care products that can be used on PFAS sites.
Of course, it is always wise to review existing reports and any available boring logs for the site. If there is little background information available for the site, then at a minimum you would want to run an array of HPT logs across the proposed investigation area, especially adjacent to proposed groundwater sampling locations, if they have been identified. The HPT logs will quickly identify zones of permeability in the formation where you can successfully sample groundwater and low permeability zones where the formation will not yield sufficient water for groundwater sampling (you don’t get water from a tight silt-clay layer). Then if you are going to sample groundwater from just one or two depths at each location I would consider using either the SP16 or SP22 sampling systems. The newly modified SP22 system using 3/4-inch PVC riser with the integral mechanical syringe pump (MSP) would provide high integrity samples for PFAS sampling. If you need to profile groundwater at multiple depths for PFAS (or other contaminants) at each location you may want to check out the 175GWP with MSP . This is especially effective where you have thick zones of coarse-grained materials and need to do multiple interval sampling
Be sure to practice good decontamination procedures between each sample location. This is critical for the low concentration PFAS work. Periodically collect a rinsate sample from the groundwater tools/components that have sample contact after decontamination is conducted. Send this to the lab for analysis with the samples. Also collect a sample of the PFAS free water supplied by the lab and used to perform the rinsate tests. You can send this to the lab with the samples and have it held to see what the rinsate test results look like. If the rinsate tests and/or multiple samples come back positive at similar levels for the same compounds, you will want to analyze that PFAS free blank water.
Video: Geoprobe® SP16 Groundwater Sampler