Blog   |   Mar 6th, 2018 TRC’s Ingenious Approach to Trapping Non-Aqueous Phase Liquids Earns U.S. Patent

Trc Napl Patent

TRC has earned a patent from the U.S. Patent and Trademark Office for developing an innovative way to trap non-aqueous phase liquids (NAPLs) from groundwater or sub-surface soil to prevent them from hampering the effectiveness of a permeable reactive barrier (PRB).

The design makes use of the physical properties of light non-aqueous phase liquids (LNAPLs) and dense non-aqueous phase liquids (DNAPLs) to contain them behind barriers – where they can be sequestered or removed – while allowing the dissolved-phase contaminants to flow through the treatment media of the PRB. This design is particularly useful in applications near the source area where NAPLs may be present.

This patent is the latest in a series of TRC patents that address NAPL-containing soil and sediment.

Permeable reactive barriers can be an effective and low-maintenance technology to treat contaminated groundwater.  These barriers are typically designed to treat dissolved-phase constituents in groundwater by placing a permeable wall of reactive treatment media in the path of the plume of contaminated groundwater. 

As groundwater flows through the permeable treatment media, the contaminants are removed by precipitation or other chemical reaction. The effective life of these barriers is calculated based on the mass loading of the constituent and the reaction capacity of the treatment media.

However, because a PRB is designed to treat dissolved-phase constituents, NAPLs can render it ineffective by:

  • Prematurely consuming the treatment capacity of it
  • Physically fouling it
  • Blocking the flow of groundwater through it

TRC’s patented design solves that problem by trapping the NAPLs before they flow through the treatment media. The process involves the use of sump to collect DNAPLs and a hanging baffle to collect LNAPLs. 

If your project involves NAPLs as well as dissolved-phase groundwater impacts, it may be a candidate for the NAPL-trapping PRB technology.  Please contact TRC’s John Rice (  We can help you evaluate your site and potential remedial options.

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Blog Author

​John Rice, PE, PH

​John Rice, PE, PH

John Rice is a consulting engineer and hydrologist working out of TRC’s Madison, Wisconsin office. He has over 26 years of experience in the environment field. John provides technical expertise in surface water and groundwater hydrology, sediment and groundwater remediation. He has designed and overseen the successful construction of sediment remediation systems, including complex dredging and capping alternatives. He has also designed and installed active groundwater and soil remediation systems that include innovative in-situ remedies. John is a leader in the development of new conceptual models for migration of liquid coal tar and of recalcitrant organics from sediment. These efforts have yielded new understanding of risks and appropriate remedies. John was awarded a patent for an innovative approach to facilitate the in-situ degradation of chlorinated organic compounds and has patent applications awarded and pending for improved sediment cap designs. John is active in the advancement of the profession through the presentations and publication of professional articles. Contact John at