Dimensioning and localization of In-Situ injections
Cooperation between consultant and remediator
Situation
PFAS contamination was measured at a firefighting training site in Arboga, Sweden. As the contamination began to run off the site, remediation was required. For the design of the in-situ remediation, iFLUX was called in. Because the soil consisted of a top layer on a layer of rocks, injection would create a layer on top of the rocks that would then spread horizontally. Therefore, flux measurements were used to map this horizontal movement.
In this project that was researched by RGS Nordic, Regenesis subsequently used the data to carry out optimization of their in-situ remediation approach.
Sampling
At the time of this project, theiFLUX PFAS cartridgein close collaboration withCyclopurewas not yet developed. Therefore, water fluxes were measured and directional measurements were made. These gave an indication of the underground dynamics of groundwater and thus the mobile components of PFAS.
The iFLUX samplers were installed in 3 monitoring wells with a diameter of 41/50 mm (ID/OD). A total of 5 cartridges were used. These were collected again after 18 days of exposure. Water flux was measured at 5 locations. Three of them at depths between 2.4 and 2.94 m and two of them at depths between 3.3 and 3.4 m.
On top of that, three directional measurements were made at a depth between 2.95m and 3.3 m.
"The data collected, using the iFLUX technology, has a major impact on the design of the in-situ solution. With most preliminary site investigations, I start with the question 'Can we install iFLUX cartridges here?"
- Jack Shore Regenesis
Challenges
Optimize in-situ remediation as function of underground dynamics:
Mobile contamination (PFAS) where there is uncertainty about mobility
Influence of rock layer on horizontal dispersion of contamination
How to optimize in-situ injection techniques with flux data?
The Solutions
iFLUX offers insight into underground dynamics to improve remediation accordingly:
Measurements of groundwater flow velocity and direction
iFLUX cartridges map horizontal movement
Flux measurements map potential preferential pathways that help to optimize remediation. On top of that, directional measurements provide insight into the direction in which Regenesis'PlumeStop solution would work best
The Result
The analysis of the flux results gave a clear understanding of the preferential groundwater pathways. One higher flux value was observed, indicating a preferential pathway where the PFAS contamination would move faster. This valuable information could help in optimizing the in-situ remediation, for example by injecting more at the location of this preferential path.
The directional measurement was also important for Regenesis (in collaboration with RGS Nordic) for their "PlumeStop" solution. To prevent a further spreading of the PFAS contamination, it was important to inject it downstream in the direction of the spread.
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