Travis AFB — SERDP PFAS Study

Setting

Military airfields used aqueous film-forming foam (AFFF) for decades to fight fuel fires, and AFFF works because of PFAS: the per- and polyfluoroalkyl substances that do not break down. Where the foam was used, PFAS followed it into the soil and groundwater, and the Department of Defense is now investigating thousands of such sites. SERDP, its environmental research program, funds the studies that make that work reliable.

The question

PFAS are measured in parts per trillion, and they turn up in everyday materials. So before a sample result can be trusted, the equipment that collected it has to be ruled out. Monitoring wells are often fitted with dedicated tubing that stays in the well between sampling events for years. Could that tubing, or new tubing put in its place, add PFAS to the water it carries, or hold PFAS back? If it could, results across a monitoring network would carry a bias no one could see.

The study

We tested it directly across about half a dozen wells. At each one:

1. Sample through the existing tubing, the way the well is normally sampled.
2. Pull the existing tubing and sample the tubing itself, with a methanol rinse run through it to recover any PFAS held on its walls.
3. Drop in new tubing and sample the well again.
4. Return the existing tubing to the well, so its monitoring carries on as before.

Comparing the results well by well (water through old tubing, water through new tubing, and what the tubing itself held) shows whether the tubing adds or removes PFAS, and whether dedicated tubing can stay in place.

My role

I provided field study and groundwater sampling support: running the sampling sequence at each well and collecting the water and tubing-rinse samples the study was built on.

Sampling for parts per trillion

A study of sampling bias cannot bring its own bias, so the field protocol is the product:

• PFAS-free field kit: no waterproof fabrics or notebooks, no Teflon near the sample; high-density polyethylene or polypropylene bottles, nitrile gloves changed at every step;
• careful purging and sampling of each well, with field parameters logged so the water in the bottle represents the aquifer;
• blanks and duplicates: field and equipment blanks that show nothing was added along the way, and duplicates that show the result repeats;
• chain of custody from the well to the laboratory.

Skills demonstrated

PFAS groundwater sampling to research-grade protocols; designing out sampling bias; tubing and methanol-rinsate sampling; field QA/QC with blanks and duplicates; and supporting a federally funded research study in the field.