Contaminant Plume
The underground zone of contaminated groundwater or soil spreading outward from a LUST release source.
A contaminant plume is the three-dimensional body of contaminated groundwater that extends from a release source, such as a leaking underground storage tank, in the direction of groundwater flow. Plumes from LUST sites typically contain dissolved petroleum hydrocarbons including BTEX compounds and, at older sites, fuel additives like MTBE.
The size and shape of a contaminant plume depend on several factors: the volume and duration of the release, the type of contaminant, groundwater flow velocity and direction, soil permeability, and the rate of natural attenuation. Petroleum plumes may extend from tens of feet to over a mile from the source, with MTBE plumes typically traveling much farther than BTEX plumes due to MTBE's higher solubility and resistance to biodegradation.
Characterizing contaminant plumes is a critical component of LUST site investigation. Monitoring wells are installed to define plume boundaries and track migration over time. Plume maps guide corrective action planning and help assess risks to nearby drinking water sources, private wells, and surface water bodies. UST Map tracks the proximity of LUST releases to these sensitive receptors.
Related Terms
The pollution of underground water sources by petroleum products or hazardous substances from leaking USTs or other sources.
BTEX (Benzene, Toluene, Ethylbenzene, Xylenes)A group of volatile organic compounds commonly found in petroleum products and frequently detected at LUST sites.
MTBE ContaminationEnvironmental pollution by methyl tert-butyl ether (MTBE), a gasoline additive that readily dissolves in and contaminates groundwater.
Corrective ActionThe investigation and cleanup activities required when a release from an underground storage tank is confirmed.