Groundwater Protection Unit :: In situ Groundwater Remediation
Injection wells can be used for groundwater remediation in several ways:
Other wells which may be associated with groundwater remediation sites include:
Closed-loop groundwater remediation
Contaminated groundwater is withdrawn, treated to reduce the concentration of contaminants, and reintroduced into the subsurface via an injection well or infiltration gallery. This includes conventional pump and treat systems with only above-ground treatment as well as innovative systems where some or all of the treatment occurs in the subsurface, but contaminated groundwater is used as the fluid source. A non-discharge permit for groundwater remediation is required for these systems. A separate injection well permit is not needed.
In situ groundwater remediation
Substances are injected to break down contaminants by chemical or biological means or to assist in their removal by physical means. A Type 5I injection well permit is required for construction and operation of this type of system.
In addition to the permit requirement, any new substance to be injected to promote in situ remediation must be reviewed by the Occupational and Environmental Epidemiology Section (OEES) of the Division of Public Health, Department of Health and Human Services. The purpose of this review is to evaluate the inherent health risks of the substance itself. Click here for a list of approved injectants. If you do not see the substance you are considering for injection on this list, please contact the UIC Program before submitting a permit application.
Air sparging for aeration
Ambient air is injected under pressure into a well in order to volatilize contaminants and to stimulate aerobic bioremediation. No injection well permit is required for construction or operation of air sparging wells as long as only ambient air is being injected. If any other substances are added to the air stream, such as oxygen, ozone, or other gases or vapors, a Type 5I injection well permit is required.
Tracer injection wells
An aqueous solution containing a dye or chemical tracer is injected into a well and its presence is monitored at monitoring or recovery wells in order to determine groundwater flow paths. A Type 5T injection well permit is required for construction and operation of tracer injection wells.
In addition to the permit requirement, any new substance to be injected as a tracer must be reviewed by the Occupational and Environmental Epidemiology Section (OEES) of the Division of Public Health, Department of Health and Human Services. The purpose of this review is to evaluate the inherent health risks of the substance itself. Click here for a list of approved injectants.
Aquifer test wells
These wells are used to estimate aquifer parameters, such as by slug testing using a slug of water rather than a solid slug or in situ constant head permeability testing. No injection well permit is required for construction or operation of an aquifer test well, but the injected fluid must be uncontaminated and the operation of the well must not cause contaminated groundwater to migrate into previously uncontaminated areas or cause an exceedance of groundwater quality standards.
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