- Emerging Contaminant Detection
The release of emerging contaminants from a firefighting foam concentrate spill required an innovative approach to delineate source impacts that would be cost-effective and provide rapid data to support cleanup efforts. Traditional investigation methods would have been expensive and time-consuming. We applied a novel approach that proved effective, fast and much more affordable.
Like many facilities with aboveground petroleum storage tanks, this facility required a responsive fire suppression system. The system uses aqueous film-forming foam (AFFF), a common firefighting solution. The foam concentrate uses per- and polyfluoroalkyl substances (PFASs) that help blanket a fire and deprive it of oxygen.
When an estimated 1,060 gallons of AFFF concentrate was released from containment tanks in a dedicated storage building, the foam concentrate flowed through the floor drains, discharging directly to the surface soils on-site.
The Texas Commission on Environmental Quality’s (TCEQ) established cleanup requirements are very low, in the parts per billion and parts per trillion range. This makes preventing false-positive results and collecting meaningful samples critical.
The confidential client retained our team to perform a site investigation and serve as owner’s engineer during remediation in close coordination with its contractors. Off-site laboratory testing for PFASs can be expensive and time-consuming, which is not conducive to performing rapid-response activities on a new release.
Laboratory costs are up to $270 per sample and typically take 10 working days to receive results. To overcome these limitations, we developed a new field screening approach to delineate the extent of the spill quickly and at greatly reduced cost.
The AFFF concentrate contained 15 percent to 40 percent ethylene glycol along with 1 percent to 5 percent PFASs. It is dramatically faster and less expensive to field screen soils for the presence of ethylene glycol than to send samples offsite for analysis of PFAS or ethylene glycol. Our approach hypothesized that the PFASs were collocated with the ethylene glycol and that by delineating the ethylene glycol in soils, we would define the extent of the PFAS contamination.
We collected soil samples from hand-augered borings at 17 locations, at depths ranging from 0.5 feet to 3.5 feet below ground surface. These samples were tested for the presence of ethylene glycol using a commercially available test kit and field procedures we developed.
Ten additional soil samples were collected from nine locations for laboratory analyses of six targeted PFASs for which TCEQ has established cleanup standards, as well as ethylene glycol. This was intended to assess the effectiveness of our field screening method and confirm the extent of soils containing ethylene glycol and PFASs.
The laboratory results confirmed the effectiveness of our approach. Detection or nondetection of ethylene glycol in the field correlated with laboratory analytical results and the detection or nondetection of PFAAs.
With that confirmation in hand, we used the ethylene glycol field screening to analyze samples collected from 32 hand augered boring locations, including during the excavation to help guide the removal of all affected soil by identifying clean soil at the excavation boundaries.
Finally, we collected soil samples at 18 locations within and near the boundaries after excavation for lab analysis, which confirmed that no ethylene glycol and only traces of PFASs were detected, below cleanup criteria.
By conducting field assessments for ethylene glycol, a main ingredient in AFFF concentrate, we were able to perform the necessary work in one mobilization instead of several. The ethylene glycol test kits cost about one-hundredth of what each sample test for PFASs would have cost, and our field protocols provided results in a matter of minutes rather than days.
This allowed real-time decisions to be made while guiding the cleanup effort. By sampling ahead of the backhoe during excavation of the impacted soils, we accurately determined the depth to clean soil and thus minimized the extent of the excavation, reducing the cost of disposal. An estimated 365 in-place cubic yards were excavated, with the entire clean-up completed in three days, including a day for the soil confirmation sampling activities.
Laboratory testing of confirmation samples showed that our innovative approach was successful. This approach allowed the client to address the AFFF concentrate release quickly while limiting analytical and disposal costs. The rapid response prevented the AFFF concentrate from migrating to groundwater and resulting in more costly remediation efforts.
- Site investigation
- Innovative technology application
- Rapid delineation
- Excavation guidance