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An Approach for Monitored Natural Attenuation (MNA) at a LUST Site
Citation:
WILSON, J. T. An Approach for Monitored Natural Attenuation (MNA) at a LUST Site. Presented at the EPA Region 3 States LUST Technical Workshop , Shepherdstown, WV, September 08 - 10, 2009.
Impact/Purpose:
Monitoring the changes in the concentrations of parameters which produce a “foot print” of a plume of contamination.
Description:
The primary mechanism for natural attenuation of fuel components in ground water is aerobic and anaerobic biodegradation of the components. Biodegradation reduces the concentration of oxygen, nitrate and sulfate, and increases the concentrations of iron(II) and methane. Changes in the concentrations of these parameters produce a “foot print” of a plume of contamination. EPA guidance requires that the stability of plume of contamination during Monitored Natural Attenuation (MNA) be accessed by monitoring the extension of the plume in three dimension space. This is best done by installing monitoring wells in the foot print of the plume down gradient of the source where concentrations of contaminants of concern have been brought to acceptable levels. The OWL computer application available for the Kerr Center web page can help in the selection of appropriate locations for monitoring wells. The down gradient monitoring wells should be sampled for a time interval at least as long as the time required for water to move through the source area of the plume to the monitoring well.