DWQ-2024-000870

Guidance for Storm Water Drainage Wells& the MS4 Permit
Purpose
The intent of this document is to provide guidance for the role of the MS4 operator in identifying and registering Storm Water Drainage Wells for the Utah Underground Injection Control
(UIC) Program.Storm Water Drainage Wells are a subclass of UIC Class V wells. They are used where there are is no stormwater drainage system, or in combination with a storm drain system.
In Utah, UIC programs are regulated under the Safe Drinking Water Act. This act establishes minimum requirements, technical criteria and standards for UIC programs to protect underground
sources of drinking water from endangerment by subsurface emplacement of fluids (40 CFR Parts 144-148) into UIC wells.
In Utah, UPDES Storm Water Programs are regulated under the Utah Water Quality Act which regulates discharges of storm water to “waters of the state.” In Utah “waters of the state” include
groundwater. The stormwater permitting staff works closely with the groundwater team at DWQ to ensure that all rules and regulations are followed and all requirements for the respective
programs are met.
Relevant MS4 Permit Citations
The MS4 permit requires retention of the 80th percentile storm event (Small MS4 Permit part 4.2.5.1.2.), a review of post construction controls for most development/redevelopment sites
(Small MS4 Permit part 4.2.5.3.2.), inspection/maintenance of storm water controls (Small MS4 Permit part 4.2.5.2.5.), and an inventory of all post construction controls that receive
discharges of storm water (Small MS4 Permit part 4.2.5.4.). In these cases, amongst others, the MS4 permit overlaps with storm water UIC well requirements.
MS4 Storm Water UIC Well Registration
The MS4 is required to register any MS4 owned/operated storm water drainage wells that qualify. For storm water UIC wells that the MS4 does not own/operate, the MS4 does not have obligation
to require registration of storm water UIC wells. However, any assistance in providing education of registration requirements would be greatly appreciated.
The registration form can be found on DWQ’s Storm Water Drainage Wells: Utah Underground Injection Control (UIC) Program website. The registration fee is $230 for each facility. For
MS4s, the fee is required one-time per MS4 (not per UIC well).Individual or single-family residences are exempt from UIC regulatory requirements. This exemption does not include properties
that contain multiple single-family residences (i.e, HOAs, duplexes, or neighborhoods).
Some examples of UICs that likely need to be registered are: infiltration galleries, dry wells, catchment basins with percolation, perforated pipe drains, bioretention areas, underground
chamber systems. A fluid distribution system that discharges underground through piping is typically the defining characteristic of a Stormwater UIC well.
Additional Considerations
It is a requirement of the MS4 permit that any MS4 storm water that discharges to a storm water UIC well (i.e., groundwater) is protective of water quality. This is the same for any
discharge authorized under the MS4 permit part 1.1.
In addition, if any storm water UIC controls convey or connect to the MS4’s system. The MS4 would need to ensure that these controls are inventoried, maintained, and inspected per the
Small MS4 PermitParts 4.2.5.2.5. and 4.2.5.4.