At light non-aqueous phase liquid (LNAPL) legacy sites, in addition to the traditional concerns such as groundwater and soil impacts, there are “non-traditional” concerns that may need to be addressed to gain regulatory site closure. These include sheens/seeps, methane accumulation, nuisance odors, or potentially polar metabolites in groundwater and can hinder closure of these sites, require additional data collection, evaluation, and possibly mitigation. This can lead to added project costs, despite there likely being limited to no risk. This presentation provides an overview of the traditional and non-traditional concerns regarding LNAPL at a legacy site, describes a process to proactively screen and evaluate the concerns and identify risk or non-risk remediation drivers, and briefly addresses potential mitigation measures. The goal of this presentation is to condense the science and present the materials in a systematic way that will provide a way to quickly assess which concerns, if any, need to be addressed at legacy sites to accelerate regulatory closure.

Primary Author / Conference Presenter:
Robert Frank
Principal Hydrogeologist
Tempe, Arizona, USA

Tom Palaia, Jacobs, Denver, CO