I think we can all agree that petroleum is foundational to our modern lives. Total use over the last 100 years is on the order of 10,000,000,000,000 gallons (www.eia.doe.gov). That is a lot of zeros, and a lot of petroleum. All of this has brought great convenience and quality to our lives. Unfortunately, a by‑product has been the inadvertent release of petroleum liquids into the environment, commonly referred to as LNAPL or “free product.”
The acronym LNAPL stands for light nonaqueous‑phase liquid. “light” because it is less dense than water; “nonaqueous‑phase” because it does not mix with water (i.e., floats on top of the water) and “liquid” well simply because it’s a liquid. LNAPL molecules are slightly soluble in water, thus creating a dissolved-phase contamination when LNAPL encounters groundwater. This often results in exceedances of water-quality standards.
A disadvantage of LNAPL’s low solubility is that it can persist as a source of groundwater contamination for decades, possibly centuries … some readers may know of old sites that to this day you can fuel your lawn mower with what you pull out of the ground. LNAPL has been the bane of responsible parties, and job security for many a consultant. But times they are a changin’.
In 2008, the Interstate Technology and Regulatory Council (ITRC) LNAPL Team (I am imagining the team colors are oily black, and impact gray) asked States what condition must be met to terminate active LNAPL remediation systems.
- 40% responded that “all measurable LNAPL must be remediated.”
- 40% responded that a “long-term monitoring plan” must be in place.
- 23% said engineering controls must be in place.
- 37% said institutional controls must be in place.
- 26% responded that more than one of these (monitoring and engineering and/or institutional controls) was required.
The survey was repeated in 2017, and 20 states had updated or changed their LNAPL management approach since 2008.
States are adopting new LNAPL Closure Policies, under which, if conditions are right, LNAPL can remain in the ground without remediation and without monitored natural attenuation. What? you may ask. Yes, this is happening.
States such as Arkansas, California, Delaware, Iowa, Kansas, Massachusetts, Michigan, Minnesota, Montana, Texas, Virginia, West Virginia and Wisconsin now recognize that understanding LNAPL behavior and recoverability allows for more realistic remedial objectives and better solutions.
These new guidance documents and policies are game changers. Hundreds, possibly thousands, of sites can achieve the coveted No Further Action or Closure where it had been impossible before. For example, West Virginia just released its LNAPL Sites Closure Policy in September of this year. It reads, “The document reflects a growing consensus among regulators and practitioners that interpretation of the term ‘maximum extent practicable’ [for the remediation of LNAPL] should evaluate ‘practicable’ to consider site-specific factors related to LNAPL composition, mobility, risk, and technology limitations … for VRP and UECA-LUST Program projects, a remediation goal that allows for measurable LNAPL to remain on-site, yet is protective of human health and the environment, may be considered on a site-specific basis …”
If you want to discuss LNAPL closure policies, please contact Lydia M. Work, Associate Principal Chemist and LRS.
