In Situ Groundwater Remediation

In Situ Groundwater Remediation

 Injection wells are typically used for groundwater remediation in the following ways: 

Injection of remediation compounds

Substances are injected to degrade contaminants chemically or biologically, or to assist in their physical removal by recovery wells.  Many smaller projects are deemed 'permitted by rule' and only require submittal of a notification form. Other larger projects require submittal of a permit application and issuance of an individual permit before injection or well construction can begin. Follows is the criteria for wells 'permitted by rule'.  If the criteria do not meet these standards, then a permit application needs to be submitted and a permit issued prior to the commencement of injection activities.

1) Passive Injection Systems - In-well delivery systems to diffuse injectants into the subsurface.  Examples include ORC socks, iSOC systems, and other gas infusion methods

2) Small-Scale Injection Operations – Injection wells located within a land surface area not to exceed 10,000 square feet for the purpose of soil or groundwater remediation or tracer tests.  An individual permit shall be required for test or treatment areas exceeding 10,000 square feet. 

3) Pilot Tests - Preliminary studies conducted for the purpose of evaluating the technical feasibility of a remediation strategy in order to develop a full-scale remediation plan for future implementation, and where the surface area of the injection zone wells is located within an area that does not exceed 5% (five percent) of the land surface above the known extent of groundwater contamination.  An individual permit shall be required to conduct more than one pilot test on any separate groundwater contaminant plume. 

4) Air Injection Wells - Used to inject ambient air to enhance in-situ treatment of soil or groundwater. 

5) In-Situ Thermal Wells (IST) – Used to ‘heat’ contaminated groundwater to enhance remediation. 

For approved additives to inject for remediation See a list of approved injections additives. If you do not see the substance you are considering for injection on this list, you must fill out the appropriate risk assessment evaluation form when submitting an injection well permit application or notification form: Risk Assessment form with Microbial and Non-Microbial Risk Assessment form.  Any new substance to be injected must be reviewed by the Occupational and Environmental Epidemiology Section (OEES) of the Division of Public Health, Department of Health and Human Services.  NOTE: This process may take two to three months or more. 

Air sparging

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; however, notification is required two weeks prior to injection. Deemed Permitteed  Notification of Intent (NOI) to Construct or Operate Injection Wells form  Also, a Well Constrution Record (GW-1) is required to be submitted for this type of well.

Tracer injection

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. The permitting requirements for this type of permit are the same as injecting for larger projects, found above.


Aquifer hydraulic testing

These wells are used to estimate aquifer parameters by hydraulic slug testing 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 exceeding of groundwater quality standards.

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