User Manual for Concawe LNAPL Toolbox

21 Apr 2022

LNAPL stands for “Light Non-Aqueous Phase Liquids” or hydrocarbons that exist as a separate undissolved phase in the subsurface at some sites with legacy releases of fuels. They are referred to as “Light” because most petroleum hydrocarbons are less dense than water. Because LNAPLs can sustain dissolved groundwater plumes for long time periods, it is important to understand how much LNAPL may be present at site, if the LNAPL can migrate, if it can be recovered, how the LNAPL composition changes over time, how long it may persist, and finally quickly the LNAPL body is attenuating.

Understanding LNAPL behavior is complex, and therefore Concawe envisioned compiling a unique collection of useful tools, calculators, data, and resources to help LNAPL scientists and engineers better understand how to manage LNAPL at their sites. Concawe commissioned the developed of the Concawe LNAPL Toolbox, a wide-ranging but easy to use web-based toolbox to deliver key LNAPL knowledge to the LNAPL remediation community. The LNAPL Toolbox is intended to be a clear, transparent tool that regulators can use to validate site information that is given to them and to learn about LNAPL so that they are able to make informed decisions using sound science. The toolbox uses a three-tiered approach that provides access to over 20 different LNAPL tools (key infographics, nomographs, calculators, mobility models, videos, checklists, and other formats) with different levels of complexity, activation energy, and time requirements. The three tiers of complexity are:

Tier 1: Simple, Quick Graphics, Tables, Background Information
Tier 2: Middle Level Quantitative Methods, Tools
Tier 3: Gateway to Complex Models

In terms of content, the Concawe LNAPL Toolbox is designed to address six questions via six different sections:

1. How much LNAPL is present?
2. How far will the LNAPL migrate?
3. How long will the LNAPL persist?
4. How will LNAPL risk change over time?
5. Will LNAPL recovery be effective?
6. How can one estimate Natural Source Zone Depletion (NSZD)?

The Concawe LNAPL Toolbox is designed to be accessed via a webpage on an internet browser (, or by downloading the Toolbox for use on a personal computer ( In this manual, there are standalone description of each component of the LNAPL Toolbox, such as the Overview and supporting information for each of the three Tiers in each of the 6 questions.