Prior to initiating an aquifer storage and recovery (ASR) project, it is necessary to obtain a permit that allows the recharge of water to the receiving groundwater aquifer. The permitting of ASR operations is through the U.S. Environmental Protection Agency’s Underground Injection Control (UIC). While there are several UIC classifications for recharge of different types of fluids (Class I through VI), the recharge of waters for ultimate potable uses are Class V wells. Class V permits are necessary where the recharge water is non-hazardous and is being recharged into an aquifer that is used as a source for drinking water. Recharge “wells” covered by a Class V permit include water that is recharged directly into the aquifer, i.e. injection wells, or above the local water table, i.e. rapid infiltration basins (RIBs), where the water is ultimately recharged into a drinking water aquifer.

In drinking water aquifers where an ASR project is proposed, the project may need to be permitted or can possibly by authorized by rule. A well is typically authorized by rule if the applicant submits the required well information and the recharge does not endanger any applicable drinking water standards in the receiving aquifer. If there is the potential for drinking water standards to be violated by the ASR project, this may require an individual Class V permit so that additional operating requirements are implemented in the ASR project to ensure protection of groundwater quality.

Types of water that may be able to be recharged into a drinking water aquifer with a Class V permit or an authorization by rule include:

• Drinking water from a public water treatment system;

• Untreated groundwater and surface water;

• Treated effluent; and/or

• Reclaimed or recycled water.

When reviewing applications for an ASR project in a drinking water aquifer, the UIC has identified some specific issues of concern:

• Pathogens may enter aquifers if water is not disinfected prior to injection.

• Disinfection byproducts can form in the aquifer if water is disinfected prior to injection. Soluble organic carbon should be removed from the injectate before disinfection. If not, chlorinated disinfectants may react with the carbon to form contaminating compounds. Contaminants include trihalomethanes and haloacetic acids.

• Metals and radionuclides may be mobilized from the rock depending on the chemistries of the injected water and the aquifer. Differences in pH and oxidation-reduction potential between the injected water and aquifer may cause arsenic, iron, manganese, or radionuclides that are present in the rock to dissolve into the underground source of drinking water (USDW).

• Carbonate precipitation in carbonate aquifers can clog wells when the injectate is not sufficiently acidic.

LWS has obtained both UIC authorizations by rule, as well as State recharge permits where the state has primacy, and can assist with the permitting or authorization by rule of any ASR project.

For more information on the common methods of achieving aquifer storage and the subsequent recovery of the water, have a look at our previous blog. For more information on the permitting requirements of ASR operations, please contact LWS by email or give us a call.

Phone: 303-350-4090

Bruce A. Lytle, P.E. bruce@lytlewater.com