Importance of maintaining hidden stormwater filter systems using engineered media
By: Juanita Voigt, State Aid Storm Sewer Review, MnDOT Bridge Office
Did you ever have a fish aquarium as a kid with a filter on the back that kept your aquarium clean and healthy? If so, you may relate to this situation.
Some state aid construction projects now include underground stormwater filter systems relying on engineered media to improve water quality by capturing sediment and pollutants before they reach local waterways. However, because these systems are installed entirely underground, there are no visible structures or reminders that they exist to provide reminders that they require routine inspection and cleaning.
Lack of visibility is one reason engineered media filter systems need a hero or champion to keep the design intention alive. Without clear prompts, maintenance can be easily overlooked. For cities and counties inheriting these systems through state aid projects, proactive management is essential.
To keep the filters functioning as intended, agencies should identify all system locations, schedule regular inspections, and plan for timely cleaning following the recommended protocol. Consistent maintenance is required to keep these out of sight systems working to protect local water resources and preserve the long term value of the infrastructure.
Keep an eye on hidden underground engineered media based stormwater filter systems.
- What they do: Underground media based stormwater filters capture sediment, trash, oils and other pollutants before they reach local waterbodies.
- Where they are: These engineered media systems are installed entirely underground with no visible structures, no surface features, no day to day reminders they exist.
- Why it matters: Because they’re hidden, maintenance is easy to overlook. When maintenance is missed, the filters clog, bypass flow, and stop providing the water quality benefits they were built for.
- What cities and counties should do:
- Map system locations
- Schedule regular inspections (including after major storm events)
- Plan for timely cleanouts following recommended protocol.
- Track maintenance activities and document per manufacturer.
Regular maintenance is required to keep these out of sight systems working to protect local water resources.