Remediation: Techniques and Cost - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 392

Surfactant, cosolvent,
or water mixture

Polluted groundwater
removed and cleaned up
above ground

Ground surface

Groundwater
level

NAPL

Polluted groundwater

FIGURE 11.16
Example of in situ soil flushing. (From United States Environmental Protection Agency (USEPA), A Citizen's
Guide to Soil Flushing , EPA 542-F-01-0011, Office of Solid Waste and Emergency Response, Washington, DC,
2001i.)

11.5.1 In Situ Soil Flushing

In situ soil flushing represents a modification to the traditional pump and treat system
and is employed to increase contaminant removal efficiency. With this method, water or
chemicals are pumped or percolated into saturated soil with the objective of flushing or
driving the contaminants to a location where they can be removed, usually by a pumping
well (Figure 11.16).

11.5.2 Air Sparging

Air sparging is an in situ groundwater remediation technology that uses injected air to
volatize contaminants in groundwater. As the injected air rises through the saturated zone
and reaches the unsaturated zone, the vapors containing the contaminants are removed
from the ground using a SVE system (Figure 11.17).

Air pollution
control equipment

Air in
Air injection well
(air sparging)

Extraction
well (SVE)

Water table

Pollution

FIGURE 11.17
Example air sparging system. (From United States Department of Energy, Remediation Technologies Screening
Matrix and Reference Guide , Version 4.0, Washington, DC, 2002.)