Underground Injection Well Registration in EPA's Pacific Southwest (Region 9)

EPA’s Pacific Southwest (Region 9) implements and enforces federal environmental laws in Arizona, California, Hawaii, Nevada, the Pacific Islands, and 148 Tribal Nations.

On this page:

How to Register Injection Wells
Frequently Asked Questions
Injection Well Inventory Form

How to Register Injection Wells

If you own, operate or plan to construct one or more injection wells, you are required to register those features, also known as injection wells, with the Underground Injection Control program. This requirement applies to deep and shallow subsurface disposal systems as defined in 40 CFR part 144. Compliance with the federal Underground Injection Control (UIC) regulations includes fulfilling two basic requirements: (1) - register injection well(s) and (2) - do not use injection wells in a manner that will contaminate underground sources of drinking water.

These instructions and e-Form were developed to assist injection well owners in Arizona, California, Hawaii, and Indian Tribes of the desert southwest comply with the federal UIC regulations. Other state and local regulations may apply. See the regulations at 40 CFR part 144 for more information, at the U.S. Government Printing Office.

Frequently Asked Questions

My runoff discharges to a swale, pond or ditch. Is this injection?

If there is no subsurface (buried) discharge component to the system, then it is not subject to UIC requirements, however it may be subject to Clean Water Act requirements or other water protection regulations.

The injection well serves a single family home. Do I have to register the well?

Injection wells serving single family homes do not have to submit inventory information unless they are used by a home-based business, such as car repair, pet boarding, medical services or other businesses that generate a liquid waste stream that is to be disposed underground.

I have a septic system with multiple leachfield lines. Does each leachfield pipe count as a different injection well?

No, if all of the leachfields receive effluent from the same septic tank or other treatment device, they count as components of one injection well or subsurface fluid distribution system.

Do I need an EPA permit to operate my Class V well?

Not necessarily. Most Class V wells are Authorized by Rule in EPA Region 9, meaning that the Class V injection well could operate without a permit if certain conditions are met, as described on Federal Requirements for Class V Wells. After submitting well inventory information (using the form below), EPA Region 9 will make a determination if the well(s) can be Authorized by Rule. Note that injection activities may be subject to state and local permits, as described below.

Is registering the injection well my only obligation?

Some injection activities are subject to state and local requirements and/or permits. Single-family onsite sewage systems are generally regulated by county environmental health agencies. Large capacity sanitary waste disposal and industrial discharges may be regulated by local or state water quality agencies. If your injection well(s) are subject to a discharge permit from the state, please list that permit number in the comments box to help reduce duplicative requirements.

Depending on multiple factors, such as your location in relation to drinking water supply wells or the type of injectate, your injection well(s) may be subject to additional federal requirements. These requirements may include sampling, characterization, permitting or closure of injection wells. Shallow injection of hazardous waste, untreated sewage and motor vehicle repair fluids is prohibited except in ongoing remedial actions overseen by regulatory agencies. See the regulations for more information. IMPORTANT: You must notify EPA if the ownership, well operating status or injectate changes.

How does EPA use the information?

EPA will use this information to notify you of applicable regulatory requirements or best management practices to prevent contamination. EPA shares the data with other water quality agencies, public water supply agencies, and in response to Freedom of Information Act requests for the data.

Do I need an EPA permit for any Aquifer Storage & Recovery (ASR) or Aquifer Recharge (AR) wells in California?

EPA Region 9 typically Authorizes by Rule ASR and AR wells in California as long as the well is permitted by the California State Water Resource Control Board, and meets the other Authorization by Rule requirements (see the “Do I need an EPA permit to operate my Class V well?” FAQ above). See the California State Water Resource Control Board General Order (pdf) for more information on the State requirements.

More information about AR and ASR wells can be found on Aquifer Recharge and Aquifer Storage and Recovery.

Is an abandoned drinking water well classified as a Class V UIC well?

An abandoned drinking water well may be classified as a Class V UIC well if the well is not intended for future use and has not been properly plugged and abandoned. The same classification can apply to other improperly abandoned wells, such as abandoned agricultural production wells.

Improperly abandoned wells pose a risk to groundwater by creating a direct pathway for surface contaminants to reach aquifers. If such a well is identified, it must be registered with EPA using the Injection Well Inventory Form below. It is also critical to properly plug the well to seal pathways between potential sources of contamination and aquifers.

Below are resources you can use to help properly plug and abandon wells:

Source water assessment programs (SWAPs) can help identify potential improperly abandoned wells in the assessment area. If you have any questions about the SWAP program, please reach out to r9iWells@epa.gov.

Do you need to register a drywell in Arizona with EPA?

No. As of October 15, 2025, Arizona has authority over all Class I -VI injection wells. EPA has transferred all AZ UIC Class V inventory, except for inventory on Indian lands, to the Arizona of Department of Environmental Quality (ADEQ). To register a drywell, or any UIC Class V well in the State of Arizona, please visit ADEQ’s UIC Class V Well Inventory website.

Injection Well Inventory Form

* Indicates a required field. After submitting this form, a confirmation email with the submitted form data will be sent to the address provided.

-------- TRANSACTION TYPE --------

THIS IS A: *

First Time Entry

Change to Existing Entry

UIC File ID/Registration of Existing Entry

------- FACILITY INFORMATION -------

FACILITY NAME *

PRIVATE RESIDENCE? *

True

False

STREET *

STREET 2

CITY *

STATE *

ZIP CODE *

PHONE

-------- FACILITY LOCATION --------

COUNTY

LAND ID

RCRA ID, APN, TMK or leave blank

LAND OWNERSHIP *

Private – Business or Other For-Profits

Private – Not-for-Profit Institutions

Private – Farms

Private – General (none of other 'Private' options)

Other – Individual or Household

Other – State, Local Government

Other – Tribal Government / Indian Country

Other – In General (none of any 'Other' options)

Federal Government

SELECT TRIBE NAME

LATITUDE °N

Latitudes in American Samoa should be entered as negative numbers. Free lat/long finder is latlong.net

LONGITUDE

----LEGAL CONTACT INFORMATION----

OWNER OR OTHER RESPONSIBLE PARTY

FOR WELLS OPERATED BY LEASE, THE OPERATOR IS THE LEGAL CONTACT

NAME *

EMAIL *

ORGANIZATION *

STREET

STREET 2

CITY

STATE

ZIP CODE

---------- WELL DETAILS -----------

NUMBER OF IDENTICAL WELLS REPORTED BELOW *

OPERATING STATUS OF YOUR WELL(S) *

Planned/Under Construction

Active

Inactive/Not Plugged

Plugged and Approved by Regulator

Plugged and Abandoned Without Approval

YEAR PLUGGED & ABANDONED?

If well(s) have been plugged and abandoned, enter the numerical year only.

INJECTION WELL DEPTH

(# of feet below ground surface)

< 50 Feet

50 – 500 Feet

> 500 Feet

DESCRIPTION OF WELLS AND ACTIVITIES *

Briefly describe the wells and injection activities. Include information such as the injectate, injection rate, injection depth, purpose of the wells, and the overall nature of the injection activities.

------------------WELL TYPE------------------

CATEGORY *

Select "HELP ME DETERMINE MY WELL TYPE" to view a table to help you determine the type of injection well you have.

Category	Well Type Name	Injectate	Description
Drainage	5D2 Stormwater Drainage	drainage: urban stormwater	Used to drain surface and subsurface fluids, including stormwater runoff and agricultural drainage that may have the potential to receive insignificant amounts of waste due to small volume leaks, drips, or spills
	5F1 Agricultural Drainage	drainage: rural/agricultural	Stormwater drainage originating from agricultural (animal or crop) operations
	5X13 Mine Backfill and Drainage	drainage: mining	Used to inject materials into mined out portions of subsurface mines, whether what is injected is a radioactive waste or not, including: (1) slurries of sand, gravel, cement, mill tailings/refuse, fly ash, or other solids, and (2) mine drainage
	5G30 Special Drainage	mixed/other	Overflow from landslide control, lake level, pool or related drainage sources
	5D3 Improved Sinkhole used for Drainage	drainage: rural/agricultural	Drainage of stormwater or other runoff via an improved sinkhole, a naturally occurring formation in fractured rock, such as limestone
Improperly Abandoned Water Supply	5X29 Improperly Abandoned Water Supply	mixed/other	Well formerly used for water supply that have the potential to deliver drainage directly to the water table
Sewage Treatment Effluent	5W12 Wastewater Treatment Plant Effluent Injection	sanitary waste: treated effluent	Used to inject treated effluent from POTWs, or privately owned treatment works receiving solely sanitary waste
Septic Systems	5W11 Septic Tank with undifferentiated disposal method	sanitary waste: treated effluent	Septic tank and subsurface fluid distribution system having the capacity to serve 20+ persons or more per day and used solely for the subsurface emplacement of sanitary waste
	5W31 Large capacity septic system (vertical dispersal)	sanitary waste: treated effluent	Septic tank followed by seepage pit, drywell, rockwell, cavitette, or former cesspool, with the capacity to serve 20+ persons per day and used solely for the subsurface emplacement of sanitary waste
	5W32 Large capacity septic system (horizontal dispersal)	sanitary waste: treated effluent	Septic tank followed by horizontal leach lines, drain tiles, or other soil-based treatment unit, with the capacity to serve 20+ persons per day and used solely for the subsurface emplacement of sanitary waste
Industrial	5D4 Stormwater Drainage - Industrial Flow	drainage: rural/agricultural	Stormwater drainage originating from industrial settings or loading docks
	5X17 Air Scrubber Waste Disposal, associated with Class II oilfield activities	industrial process water	Air Scrubber waste disposal that may include lime, sodium or alkali, nitrates, chlorides, sulfates and TDS
	5A8 Groundwater Aquaculture Return Flow	industrial process water	Used to inject fluids that have undergone chemical alteration during the production of geothermal energy for aquaculture
	5W20 Industrial, could be mixed with sanitary waste	industrial process water	Typically an onsite sewage system that has been plumbed to receive fluids originating from industrial or commercial activities
	5X18 Water Softener Regeneration Brine Disposal	brine	Water Treatment Residual that may include concentrations above the MCL of target contaminant, such as arsenic or radionuclides
	5A19 Cooling Water Return Flow	industrial process water	Cooling water with additives
	5A18 Industry-Cooling water with no additives	industrial process water	Cooling water with no additives
Beneficial Use	5X26 Aquifer Remediation	remedial stimulants	Injection to stimulate subsurface environmental remediation
	5R33 Aquifer Storage and Recovery	potable water	Aquifer Storage and Recovery (as opposed to aquifer recharge only, 5R21)
	5R21 Aquifer Recharge	potable water	Aquifer Recharge
	5S23 Subsidence Control	non-potable aquifer recharge water	Subsidence Control
	5B22 Saline Water Barrier Intrusion	non-potable aquifer recharge water	Saltwater Intrusion Barrier
Fluid return	5X16 Spent-Brine Return Flow	brine	Used to inject spent brines after the extraction of minerals from produced fluids
	5A5 Electric Power Return/Reinjection	geothermal fluids	Used to inject fluids that have undergone chemical alteration during the production of geothermal energy for energy production
	5A6 Direct Heat Reinjection	geothermal fluids	Used to inject fluids that have undergone chemical alteration during the production of geothermal energy for heating
	5A7 Heat Pump/Air Conditioning Return Flow	geothermal fluids	Used to inject heat pump return fluids
In-situ and Solution Mining	5X15 In-Situ Fossil Fuel Recovery	mixed/other	Used for recovery of coal, lignite, oil shales, and tar sands, through injection of steam, air, solvents, or igniting agents
In-situ and Solution Mining	5X14 In-Situ Solution Mining, such as stopes leaching	mine stimulants (lixiviants)	Used to inject fluids for the purpose of producing minerals or energy, which are not Class II or III well
Biosolids	5W9 Biosolids Disposal	sanitary waste: biosolids	Septic tank solids disposal
LCC (Banned)	5W10 Large Capacity Cesspool	sewage	Cesspools having the capacity to serve 20+ persons or more per day and used solely for the subsurface emplacement of sanitary waste: BANNED.
Motor Vehicle Waste Disposal (Banned)	5X28 Motor Vehicle Waste Disposal	motor vehicle fluids, leaks or steam cleaning	Used to inject fluids from motor vehicle repair or maintenance activities, such as an auto body shop, automotive repair shop, dealership, specialty repair (e.g., transmission/muffler repair). BANNED.
CO2	5X34 Experimental Technology used for Carbon Sequestration	liquid CO2	Injection well used in experimental technologies to capture/sequester carbon emissions from atmosphere
CO2	5X35 Post-experimental CO2 Sequestration via Class V	liquid CO2	Injection well used to capture/sequester C02, into/above USDW
Experimental Technology	5X25 Experimental Technology (except C02 projects)	mixed/other	Injection well used in experimental technologies, except C02 sequestration projects (see 5X34)
Other Class V	Shallow Injection - other (5X27)	mixed/other	Class V Shallow injection - Other
Other Class V	Class V Well - other (5X)	not specified	Class V Well - other

DRAINAGE

IMPROPERLY ABANDONED WATER SUPPLY

SEWAGE TREATMENT EFFLUENT

SEPTIC SYSTEMS

INDUSTRIAL

BENEFICIAL USE

FLUID RETURN

IN-SITU AND SOLUTION MINING

BIOSOLIDS

LARGE CAPACITY CESSPOOL (BANNED)

MOTOR VEHICLE WASTE DISPOSAL (Banned)

CARBON DIOXIDE (CO2)

EXPERIMENTAL TECHNOLOGY

OTHER CLASS V

DISPERSAL DIRECTION *

Select the predominant plumbing orientation of the injection well(s): horizontal such as a leachfield; vertical such as a drywell or seepage pit.

Horizontal

Vertical

INJECTATE SOURCES *

From This Site Only

This Site and Others

COMMENTS

Please list any local or state permits that authorize, monitor, or otherwise affect the reported injection well(s). If this site is subject to any relevant local or state permits, or if you have any operational considerations for the injection well(s) that you would like to note, please list them here.

YOUR NAME

If you are NOT the owner listed above, please enter your name here.

YOUR EMAIL

If you are NOT the owner listed above, please enter your email here.

YOUR ORGANIZATION

If you are NOT the owner listed above, please enter your organization here.