There are two types of Non-Aqueous Phase Liquids (NAPL):
Light non-aqueous phase liquids (LNAPL): are less dense than water and float on the water table surface.
Dense non-aqueous phase liquid (DNAPL): are denser than water and sink to the bottom of water table and rest on impermeable surfaces such as clays and bedrock.
NAPL recovery can be used as an ex-situ method from open excavation using floating or sinking skimmers or via in-situ remediation methods from wells or trenches installed to allow access to the free product.
Skimmer or top loading pumps are used to collect LNAPL for a low intensity recovery where time may not be the driver. Bottom loading total fluid pumps can be used for DNAPL.
NAPL is collected and filtered and then stored onsite ready for off site recycling .