Blog   |   Oct 4th, 2018 Recent Technical Advances Have Upset the LNAPL Cart – In a Good Way

Trc Lnapl Technical Advances

Key guidance documents updated for first time in years

When it comes to managing liabilities posed by petroleum hydrocarbons in the form of light, non-aqueous phase liquid (LNAPL), is your attitude “been there, done that?” Well, it’s probably time to rethink that position.

Technical developments over the last few years have led to fundamental changes in how sites contaminated by LNAPL are assessed and remediated. These developments offer site owners and responsible parties the opportunity to dramatically improve the efficiency of site remediation efforts while significantly lowering costs. 

Given the magnitude and significance of these technical developments, two leading organizations have updated their LNAPL guidance documents. 

The Interstate Technology and Regulatory Council (ITRC) issued its original guidance documents in 2009.  Its updated guidance document, “LNAPL Site Management: LCSM Evolution, Decision Process, and Remedial Technologies,” was released in March 2018 and is available online. (Disclosure: My TRC colleague, Kate Fogarty, and I were technical contributors to the ITRC.)   

In addition, the American Petroleum Institute (API) released “Bulletin 18: Answers to Frequently Asked Questions about Managing Risk at LNAPL Sites” in May. That document is an update to its original 2003 guidance.  Both versions are available online.

Dr. Tom Sale of Colorado State’s Center for Contaminant Hydrology – one of the nation’s premier researchers on LNAPL fate, transport and remediation – is a co-author of the API LNAPL guidance documents.  TRC recently spoke to Dr. Sale to get his take on the updated API guidance and the current state of LNAPL site management.

Why did API decide it was time to update their 2003 guidance?

The first edition of Bulletin 18 was a "best seller" for the remediation industry.   A decade later, given the importance of recent technical developments, it was decided that it should be updated.  As it turned out, the second edition wasn't a matter of a simple update; it proved to be essentially starting all over again. Demonstratively, 80 percent of the references in the second edition are new. 

What is the biggest development in LNAPL risk management since 2003?

By far the biggest new development was recognizing natural source zone depletion (NSZD) and its implications. Implications include:

  • NSZD is a primary factor limiting lateral translation or expansion of LNAPL bodies.
  • The primary direction of carbon flow out of LNAPL zones is upward, not horizontal.
  • LNAPL sites evolve through time with different characterization methods, risks and remedies needed for early-, middle- and late-stage sites.
  • Even when active remedies are employed, NSZD is typically the primary remedy for middle- and late-stage LNAPL sites, whether anyone knows it or not.

What changes in LNAPL risk management do you foresee in the next 15 years? 

With our current technical understanding, we can now see that methods developed and implemented for monitoring of early-stage sites (active releases and expanding LNAPL bodies) make little sense for today’s middle- and late-stage LNAPL sites.  Much of our current site monitoring practices for LNAPL sites will be replaced by sensors connected to the cloud, cloud-based analytics, real time dashboards, automated alerts and artificial intelligence. We are going to a place where better data, real-time realization of problems and lower cost will support better decisions regarding managing risks at LNAPL sites.  

Research in recent years has revealed that rates of LNAPL mass loss through NSZD are much greater than historically thought to be the case.  NSZD rates should be quantitatively incorporated into strategies for LNAPL site remediation and risk management. 

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Blog Author

Keith Piontek, PE

Keith Piontek, PE

Keith Piontek is a professional engineer with 30 years of experience in the assessment and management of environmentally impaired railroad properties. He leads TRC’s LNAPL site characterization technical support group and manages TRC’s St. Louis and Kansas City offices. Keith has authored 15 technical papers on topics dealing with site remediation policy, strategy, and technologies. Topics have included natural attenuation, in situ bioremediation, the technical practicability of groundwater restoration, and risk-based corrective action. Contact Keith at