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Underground Injection Control (UIC)

Stormwater Drainage Wells

On this page:

What is a stormwater drainage well?
What is not a stormwater drainage well?
Why does EPA regulate stormwater drainage wells?
What are the minimum federal requirements for stormwater drainage wells?
What are stormwater drainage well best management practices?

This page will help owners and operators:

  • Determine whether you have a stormwater drainage well
  • Learn how to comply with regulations for stormwater drainage wells
  • Find out how to reduce the threat to ground water from your injection well.

The general information may also be useful to state, tribal, and local regulators.

In general, owners and operators of stormwater drainage wells include:

  • State, tribes, and local governments
  • Public and private institutions
  • Commercial and industrial facilities
  • Community associations
  • Private citizens

What is a stormwater drainage well?

Class V stormwater drainage wells are use subsurface infiltration to manage surface water runoff (rainwater or snow melt). Stormwater drainage wells may have a variety of designs and are often refered to by names that include:

  • Dry wells
  • Bored wells
  • Infiltration galleries

The names can be misleading so it is important to note that storm water drainage wells like any well is defined in the UIC regulations (40 DFR144.3) as:

A bored, drilled, or driven shaft whose depth is greater than the largest surface dimension; or, dug hole whose depth is greater than the largest surface dimension; or, an improved sinkhole; or, a subsurface fluid distribution system.

Stormwater infiltration systems with piping to enhance infiltration capabilities meet the UIC definition of a Class V well.

""Stormwater flows into a concrete chamber. The chamber allows time for the settling for solids.  Stormwater is passed through an oil absorbent matrix prior to entering an infiltration chamber where it may be subjected to additional pretreatment. 

In 1999, EPA completed a study of Class V wells to develop background information for use by the Agency to evaluate the risks to underground sources of drinking water (USDWs) posed by Class V wells.  The study describes 23 categories of Class V wells, including stormwater drainage wells, and characterizes their:

  • Use
  • Location
  • Number
  • Potential impacts to USDWs
  • Regulatory requirements

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What is not a stormwater drainage well?

Some types of infiltration systems do not meet the definition of Class V stormwater drainage wells. These generally:

  • Are larger at their widest surface point than they are deep
  • Do not contain any perforated pipes or drain tiles to distribute and/or facilitate subsurface fluid infiltration

Surface impoundments do not include dug, drilled, or driven shafts and are not Class V wells.

Answer the following questions to determine if you have a Class V storm water drainage well.
Questions: If Your Answer Is Yes... If Your Answer Is No...
1. Do you operate a stormwater collection system that relies on infiltration to collect and dispose of storm water runoff? Go to question 2. You do not have a Class V stormwater drainage well. Stop here.
2. Does your infiltration system discharge to the subsurface? Go to question 3. You do not have a Class V stormwater drainage well. Stop here.
3. Does your stormwater infiltration system consist of a drilled or driven shaft, or dug hole that is deeper than it is wide? Does it rely on a naturally occurring sinkhole? Does it include any subsurface piping? You have a Class V stormwater drainage well and are subject to Class V requirements. You do not have a Class V stormwater drainage well. Stop here.

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Why does EPA regulate stormwater drainage wells?

The Safe Drinking Water Act requires that EPA protect USDWs from injection activities. EPA has set minimum standards to address the threats posed by all injection wells, including stormwater drainage wells. 

Stormwater injection is a concern because storm water may contain petroleum or other organic compounds that could harm USDWs. Other potential harmful contaminants include:

  • Sediment
  • Nutrients
  • Metals
  • Salts
  • Microorganisms
  • Fertilizers
  • Pesticides

What are the minimum federal requirements for stormwater drainage wells?

This section outlines the minimum federal requirements for stormwater drainage wells. Some states have applied for and been granted authority to implement the Class V UIC Program in their state, including oversight of stormwater drainage wells, and may have more stringent requirements.

Visit the permitting authority page to find out what agency oversees Class V wells in your state.  It is your responsibility to find out what the specific requirements are in your state.

Class V stormwater drainage wells are “authorized by rule,” which means they may be operated without an individual permit so long as:

  • The injection does not endanger a USDW
  • The owner or operator of the well submits basic inventory information about the well to their permitting authority

Inventory submission requirements vary by state. The required inventory information typically includes:

  • Facility name and location
  • Name and address of a legal contact
  • Ownership of property
  • Nature and type of injection well(s)
  • Operating status of the well(s) 

For more information, visit the page on minimum requirements, or contact your permitting authority.

If you have a new stormwater drainage well, you must contact your permitting authority before you begin construction.  

For existing stormwater drainage wells, you must stop using the well immediately and contact your permitting authority to find out what you must do. In most cases, you will need to:

  • Submit an inventory form
  • Wait up to 90 days to allow the UIC program to authorize your well, after which you may continue using it (unless you are told otherwise)

Authorization to use the well expires once you have properly closed the well.  Proper well closure, also referred to as well abandonment, is a procedure to ensure that the well will not endanger USDWs in the future.  Depending on the well’s design, proper well closure could include:

  • Backfilling with clean fill material
  • Soil excavation
  • Casing removal
  • Grouting

Contact your permitting authority for specific instructions on properly closing the well.

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What are stormwater drainage well best management practices?

Best management practices (BMPs) are physical, structural, and managerial practices that prevent or reduce the contamination of USDWs. The proper design and siting of a stormwater drainage well minimizes the likelihood of accidental or routine contamination resulting from either poor operational practices or misuse. 

There are five general categories of BMPs for stormwater drainage well BMPs that can be implemented alone or in combination.  The five general categories relate to: 

  • Siting 
  • Design
  • Operation and maintenance
  • Education and outreach
  • Proper closure (plugging and abandonment) 

The appropriateness and effectiveness of BMPs vary according to the type, design, setting, and operation of the well. Consult your permitting authority for additional information and to learn about location-specific BMPs.

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