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N.C. Department of Environment and Natural Resources

NC Department of Environment and Natural Resources
Water Quality - Stormwater Injection

Water Quality
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Aquifer Protection Section

Groundwater Protection Unit :: Stormwater Injection

This page contains information about stormwater drainage wells authorized by the new injection well regulations effective May 1, 2012.  Detailed information about stormwater management is available from the DWQ Wetlands and Stormwater Branch and the DWQ Stormwater BMP Manual.

For additional information contact Thomas Slusser at 919-807-6412.

 

 

What is stormwater injection?

Stormwater injection is the emplacement of stormwater into the subsurface via a well, subsurface distribution system, or sinkhole and other natural depressions.  Certain stormwater infiltration systems meet the regulatory definition of an injection well.  Injection wells are regulated by the Underground Injection Control (UIC) Program.

Is stormwater injection legal in North Carolina?

Injection well regulations adopted in 1997 prohibit stormwater injection.  However, revised regulations effective May 1, 2012, allow stormwater injection under certain conditions. This revision was made to eliminate a regulatory conflict between the 1997 injection well rules prohibiting stormwater injection and stormwater BMPs that promote stormwater infiltration as a means of protecting surface water quality and enhancing groundwater recharge.

Is stormwater injection an environmental concern?

Many of the same concerns about stormwater runoff entering surface water bodies also apply to groundwater, which provides approximately half North Carolina's water supply needs.  Stormwater runoff may contain automotive fluids, metals, nutrients, salts, fertilizers, pesticides, and microorganisms.  Proper treatment and infiltration of stormwater is an important part of protecting North Carolina's groundwater resources. 

What regulations apply?

Injection well rule 15A NCAC 02C .0227 specifies that stormwater injection is only allowed to occur via rooftop runoff infiltration systems or infiltration systems that are designed and operated in accordance with federal or state stormwater regulations.  Untreated stormwater shall not be emplaced directly into any aquifer and the operation of any stormwater injection well cannot result in the violation of any groundwater quality standard specified in 15A NCAC 02L.

Stormwater infiltration systems subject to State and local government stormwater regulations do not need a separate permit from the UIC Program.  Rather, a notification form shall be submitted to the UIC Program in order to comply with federal injection well inventory reporting requirements.

Which types of stormwater BMPs need to be reported as injection wells?

 Stormwater infiltration systems that use subsurface distribution systems, drain tiles, perforated or open-bottom pipes, or similar mechanisms designed emplace stormwater into the subsurface.  Many different system designs are possible.  The following table lists various types of stormwater BMPs and indicates which ones need to be reported to the UIC Program.

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Which Stormwater BMPs Are Regulated As Injection Wells

 

 

Stormwater BMP Description Report As An Injection Well?
Commercially Manufactured Stormwater Infiltration Devices Includes a variety of pre-cast or pre-built proprietary subsurface detention vaults, chambers, or other devices designed to capture and infiltrate stormwater runoff into the subsurface.   Yes, since their designs often meet the injection well definition of subsurface fluid distribution system.
Downspout Disconnection A practice where downspouts are directed to permeable surfaces where runoff can infiltrate.   No
Filter Strips and Vegetated Buffers Vegetated buffers are areas of natural or established vegetation maintained to protect the water quality of neighboring areas. Buffer zones slow stormwater runoff, provide an area where runoff can infiltrate the soil, contribute to groundwater recharge, and filter sediment.  Slowing runoff also helps to prevent soil and stream bank erosion. No
French Drains with Piping French drains with piping are a type of infiltration trench with piping.  Refer to Infiltration Trenches and Basins with Piping or Open Bottom Arches for guidance. Yes
French Drains without Piping French drains without piping are a type of infiltration trench without piping.  Refer to Infiltration Trenches and Basins without Piping or Open Bottom Arches for guidance. No
Infiltration Trenches and Basins with Piping or Open Bottom Arches An infiltration trench is a rock-filled trench designed to receive and infiltrate stormwater runoff. An infiltration basin is an open basin designed to receive stormwater runoff and allow it to infiltrate into the subsurface.  Runoff may pass through one or more pretreatment measures, such as a swale, prior to entering the trench or basin.  The trench or basin is designed with an assemblage of perforated pipes, open bottom arches, drain tiles, or other similar mechanisms intended to distribute fluids into the subsurface. Yes
Infiltration Trenches and Basins without Piping or Open Bottom Arches An infiltration trench is a rock-filled trench designed to receive and infiltrate stormwater runoff. An infiltration basin is a normally dry basin designed to receive stormwater runoff and allow it to infiltrate into the subsurface.  Runoff may pass through one or more pretreatment measures, such as a swale, prior to entering the trench or basin.  Pipes and other conveyances may be used to direct stormwater to the trench or basin, but there is not pipe or open bottom arches within the trench or basin itself. No
Permeable Pavement Permeable pavement is a porous or pervious pavement surface, often built with an underlying stone reservoir that temporarily stores surface runoff before it infiltrates into the subsoil. Permeable pavement is an environmentally preferable alternative to traditional pavement that allows stormwater to infiltrate into the subsoil. There are various types of permeable surfaces, including permeable asphalt, permeable concrete and even grass or permeable pavers. No
Rain Gardens & Bioretention Areas Rain gardens and bioretention areas are landscaping features adapted to provide on-site infiltration and treatment of stormwater runoff using soils and vegetation. They are commonly located within small pockets of residential land where surface runoff is directed into shallow, landscaped depressions; or in landscaped areas around buildings; or, in more urbanized settings, to parking lot islands and green street applications. No
Reforestation Reforestation can be used throughout a community to reestablish forested cover on a cleared site, establish a forested buffer to filter pollutants and reduce flood hazards along stream corridors, provide shade and improve aesthetics in neighborhoods or parks, and improve the appearance and pedestrian comfort along roadsides and in parking lots. No
Sand Filters A sand filter is a surface or subsurface device that percolates stormwater down through a sand media where pollutants are filtered out. Sand filter effluent is either infiltrated or discharged through an underdrain. No
Tree Boxes & Planter Boxes Tree boxes and planter boxes are generally found in the right-of-ways alongside city streets. These areas provide permeable areas where stormwater can infiltrate. The sizes of these boxes can vary considerably. No
Vegetated Landscaping Self-Explanatory. No
Vegetated Swales Swales (e.g., grassed channels, dry swales, wet swales, or bioswales) are vegetated, open-channel management practices designed specifically to treat and attenuate stormwater runoff. As stormwater runoff flows along these channels, vegetation slows the water to allow sedimentation, filtering through a subsoil matrix, and/or infiltration into the underlying soils. No
Wetlands and Ponds Wetlands and ponds are structural practices similar to wet ponds that incorporate wetland plants into the design. As stormwater runoff flows through the wetland, pollutant removal is achieved through settling and biological uptake. Several design variations of the stormwater wetland exist, each design differing in the relative amounts of shallow and deep water, and dry storage above the wetland. No

 

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