an organic substance that is relatively insoluble in water and more dense than water

A NAPL more dense than water (see NAPL).

Dense non-aqueous phase liquid. See non-aqueous phase liquid.

Dense Nonaqueous Phase Liquid

Dense Non-Aqueous Phase Liquid Non-aqueous phase liquids that sink through the water column until they reach a confining layer. Because they are at the bottom of aquifers instead of floating on the water table, typical monitoring wells do not indicate their presence.

Dense Non-Aqueous Phase Liquid or those liquids that are heavier than water