US EPA’s Program to 

Regulate the Placement 

of Waste Water and other 

Fluids Underground

Why Do We Need a Program to 

Regulate the Placement of Fluids 

Underground?

Facilities across the nation discharge a variety of 

hazardous and nonhazardous fluids into underground 

formations through more than 800,000 injection 

wells. Our way of life would be quite different without 

injection wells. Agribusiness and the chemical and 

petroleum industries as we know them today, could 

not exist. While treatment technologies exist, it would 

be cost prohibitive to treat and release to surface 

waters the trillions of gallons of wastes that industries 

produce each year. When wells are properly sited, 

constructed, and operated, underground injection is 

an effective and environmentally safe alternative to 

surface disposal.

The Underground Injection Control (UIC) Program 

provides these safeguards so that injection wells do 

not endanger drinking water. 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 41 percent of our streams and 

rivers, particularly during dry periods; and serve as 

resources for 89 percent of public water systems in 

the United States.

What Is an Injection Well?

An injection well is used for subsurface emplacement 

of fluids. An injection well is a bored, drilled, or 

driven shaft whose depth is greater than the largest 

surface dimension; or, a dug hole whose depth is 

greater than the largest surface dimension; or, an 

improved sinkhole; or, a subsurface fluid distribution 

system. This definition covers a wide variety of 

injection practices that range from more than 

140,000 technically sophisticated highly monitored 

wells which pump fluids into isolated formations up 

to two miles below the Earth’s surface, to the far 

more numerous on-site drainage systems, such as 

septic systems, dry wells, and storm water wells, that 

discharge fluids a few feet underground.

How Does the UIC Program 

Regulate the Very Different Types of 

Underground Injection?

United States Enivronmental Protection Agency 

groups underground injection into five 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.

• Class I injects 

hazardous and 

nonhazardous 

fluids (industrial 

and municipal 

wastes) into 

isolated formations 

beneath the 

lowermost 

underground 

source of drinking 

water (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 III injects fluid associated with solution 

mining of minerals.

• Class IV addresses injection of hazardous or 

radioactive wastes into or above a USDW and is 

banned unless authorized under other statutes for 

ground water remediation.

• Class V includes all underground injection not 

included in Classes I-IV. Generally, most Class V 

wells inject nonhazardous fluids into or above a 

USDW and are on-site disposal systems, such as 

floor and sink drains which discharge to dry wells, 

septic systems, leach fields, and drainage wells. 

Injection practices or wells which are not covered 

by the UIC Program include single family septic 

systems and cesspools as well as non-residential 

septic systems and cesspools serving fewer than 

20 persons that inject ONLY sanitary waste water.

SAFE DRINKING WATER ACT 1974 - 2004 PROTECT OUR HEALTH FROM SOURCE TO TAP

CLASS I WELL
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. But 

most injection wells have the potential to inject fluids 

that may cause a 

public water system 

to violate National 

Drinking Water 

Standards. These 

standards provide 

our safety net 

against waterborne 

disease and other 

health risks.

How Does US EPA’s UIC Program 

Prevent Contamination of Our Water 

Supply?

In general, US EPA’s UIC Program prevents 

contamination of water supplies by setting minimum 

requirements for state UIC Programs. A basic concept 

of US EPA’s UIC Program is to prevent contamination 

by keeping injected fluids within the intended injection 

zone, or in the case of injection directly or indirectly 

into a USDW, the fluids must not endanger or have 

the potential to endanger a current or future public 

water supply. Most of the minimum requirements that 

affect the siting of the injection well, the construction, 

operation, maintenance, monitoring, testing, and 

finally, the closure of the well, are designed to 

address these concepts. Another basic concept is that 

all injection wells require authorization under general 

rules or specific permits. Finally, states are expected 

to have primary enforcement authority (primacy) 

for the UIC Program. To date, 33 states, Guam, 

Commonwealth of the Mariana Islands, and Puerto 

Rico have obtained primacy for all classes of injection 

wells. Seven states share primacy with US EPA. The US 

EPA administers UIC programs for the remaining ten 

states, and all other federal jurisdictions and Indian 

Country.

The UIC Program Protects More Than 

Ground Water

The UIC Program:

• Reduces human exposure to organic and 

inorganic chemicals and heavy metals by removing 

them from the environment;

• Eliminates more than nine billion gallons of 

hazardous waste and a trillion gallons of oil field 

waste from the environment each year;

•Decreases public water system costs for water 

treatment; 

• Avoids cost of ground water remediation, 

medical monitoring for health effects, and 

replacing a drinking water supply; 

• Reduces pollution in wellhead and source water 

protection areas, rivers, streams, lakes, wetlands, 

watersheds, estuaries and coastal zones; and 

• Enables communities to make wise local land 

use decisions.

For More Information

To learn more about underground injection control, 

call the Safe Drinking Water Hotline at 1-800-426-

4791 or visit the safewater web site at www.epa.

gov/ safewate r.

Office of Water (4606) www.epa.gov/safewater EPA 816-F-04-040 June 2004

CLASS V WELL - Aquifer Remediation Well