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What is Underground Injection?

Underground injection is the technology of placing fluids underground, in porous formations of rocks, through wells or other similar conveyance systems. While rocks such as sandstone, shale, limestone appear to be solid, they can contain significant voids or pores that allow water and other fluids to fill and move through them.  The fluids may be water, wastewater or water mixed with chemicals.

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Why Do We Need a Program to Regulate the Placement of Fluids Underground?

When wells are properly sited, constructed, and operated, underground injection is an effective and environmentally safe method to dispose of wastes.  The Safe Drinking Water Act established the Underground Injection Control (UIC) Program to provide safeguards so that injection wells do not endanger current and future underground sources of drinking water (USDW).  The most accessible fresh water is stored in shallow geological formations called aquifers and is the most vulnerable to contamination. These aquifers feed our lakes; provide recharge to our streams and rivers, particularly during dry periods; and serve as resources for 92 percent of public water systems in the United States.

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What Is an Injection Well?

The UIC Program defines an injection well as any bored, drilled or a driven shaft or a dug hole, where the depth is greater than the largest surface dimension that is used to discharge fluids underground.  A drainfield is considered to be a horizontally placed injection system, and some drainfields are covered under the UIC Program.

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How Does the UIC Program Regulate the Very Different Types of Underground Injection?

The EPA groups underground injection into six classes for regulatory control purposes. Each class includes wells with similar functions, and construction and operating features so that technical requirements can be applied consistently to the class. The NDDEQ regulates Class I and Class V UIC wells. 

• Class I includes the emplacement of hazardous and nonhazardous fluids (industrial and municipal wastes) into isolated formations beneath the lowermost USDW. Because they may inject hazardous waste, Class I wells are the most strictly regulated and are further regulated under the Resource, Conservation and Recovery Act. 
• Class II includes injection of brines and other fluids associated with oil and gas production (Class II injection wells are regulated by the ND Oil & Gas Division). 
• Class III encompasses injection of fluids associated with solution mining of minerals (Class III injection wells are regulated by the ND Geological Survey).
• Class IV addresses injection of hazardous or radioactive wastes into or above a USDW and is banned unless authorized under a supervised groundwater remediation project. 
• Class V includes all underground injection not included in Classes I-IV. Class V wells inject nonhazardous fluids into or above a USDW and are typically shallow, on-site disposal systems, such as floor and sink drains which discharge directly or indirectly to groundwater, dry wells, leach fields, and similar types of drainage wells.
• Class VI includes the injection of carbon dioxide (CO2) into deep rock formations.  This long-term underground storage is called geologic sequestration (Class VI injection wells are regulated by the ND Oil & Gas Division).
• Injection practices or wells which are NOT covered by the UIC Program include;
  • individual residential waste disposal systems that inject ONLY sanitary waste
  • commercial waste disposal systems that serve fewer than 20 persons that inject ONLY sanitary waste. 

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Are All Injection Wells Waste Disposal Wells?

All injection wells are not waste disposal wells. Some Class V wells, for example, inject surface water to replenish depleted aquifers or to prevent salt water intrusion. Some Class II wells inject fluids for enhanced recovery of oil and natural gas, and others inject liquid hydrocarbons that constitute our Nation's strategic fuel reserves in times of crisis.

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How Does the UIC Program Prevent Contamination of Our Water Supply?

Injection wells have the potential to inject contaminants that may cause our underground sources of drinking water to become contaminated. The UIC Program prevents this contamination by setting minimum requirements. The goals of the EPA's UIC Program are to prevent contamination by keeping injected fluids within the well and the intended injection zone, or in the case of injection of fluids directly or indirectly into a USDW, to require that injected fluids not cause a public water system to violate drinking water standards or otherwise adversely affect public health. These minimum requirements affect the siting of an injection well, and the construction, operation, maintenance, monitoring, testing, and finally, the closure of the well. All injection wells require authorization under general rules or specific permits.

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