A stormwater pit or catch basin collects runoff from paved surfaces and routes it toward outfalls — but collection alone does not reduce pollutant loads.

A stormwater pit and catch basin collects runoff from paved surfaces and channels it toward receiving waters — but without treatment media inside, that collection point moves pollutants downstream rather than removing them. For MS4 and NPDES permit holders, the catch basin is also the most practical location to intercept hydrocarbons, heavy metals, TSS, nutrients, and PFAS before they reach a regulated outfall. Smart Sponge® media, deployed as an Ultra-Urban® Filter insert, converts an existing catch basin into a passive treatment point with no pumps, no power, and no structural modifications.

What a Stormwater Pit and Catch Basin Actually Does — and Where It Falls Short

Catch basins and stormwater pits are designed to intercept surface runoff, capture coarse debris, and prevent sediment from immediately entering conveyance pipes. They are the first physical structure in most municipal and transportation stormwater systems, positioned at low points across parking lots, roadways, airfields, and industrial yards. Under MS4 and NPDES permit frameworks, these structures are inspection points — and inspectors expect documented evidence of pollutant reduction, not just debris collection. A standard sump-style catch basin captures gross solids but allows dissolved metals, hydrocarbons, nutrients, bacteria, and PFAS to pass through with every storm event. That gap between what the basin collects and what the permit requires is where treatment media becomes necessary.

How the Ultra-Urban® Filter Converts an Existing Catch Basin Into a Treatment System

The Ultra-Urban® Filter is a drop-in insert engineered to fit inside existing catch basins without excavation, structural modification, or active power. Smart Sponge® media sits within the insert and treats stormwater as it passes through on its way to the outlet pipe. Because the media is hydrophobic and oil-loving, it binds hydrocarbons into a stable solid — the media keeps working without wringing out or releasing captured contaminants back into the flow. Flow rates reach up to 40 GPM per square foot with under 1 PSI of back pressure, which means the insert handles storm-event volumes without causing upstream flooding or bypassing. For municipalities and DOTs managing large paved catchments under MS4 permit requirements, that combination of high flow and low back pressure is operationally critical — the system must treat water during the storm, not just during low-flow conditions.

The Ultra-Urban® Filter is also sized and configured to match the specific basin geometry and the site's contaminant profile. Because different catchments present different mixes of pollutants — a roadway catch basin may carry heavy metals and hydrocarbons, while an airfield basin may carry deicing chemicals alongside fuel residue — Smart Sponge® media formulations can be selected and combined within a single insert to address multiple treatment objectives simultaneously. This is covered in detail on Abtech's stormwater treatment for MS4 and NPDES compliance page.

Matching Smart Sponge® Media to Your Water Quality Priorities

Not every catch basin faces the same regulatory pressure or the same contaminant mix. Smart Sponge® media is available in formulations targeting specific pollutant categories, and those formulations can be combined within a single system to address multiple discharge requirements at once. The supported target contaminant categories include:

Sediment and TSS — high-porosity media captures suspended solids and particulates while maintaining flow and reducing maintenance demands.
Hydrocarbons and oil — hydrophobic, oil-loving media captures oil, grease, and hydrocarbons that contribute to sheens and degraded water quality, binding them into a stable solid.
Heavy metals — media formulations address dissolved metals that pass through standard sump collection.
Nutrients — targeted formulations reduce nutrient loads that drive downstream water quality impairments.
Bacteria — media addresses microbial contaminants in runoff from paved catchments.
PFAS — Smart Sponge® media targets per- and polyfluoroalkyl substances, an emerging regulatory priority under NPDES and MS4 frameworks.
Total Organic Carbon (TOC) — media addresses organic carbon loads that affect downstream treatment and receiving water quality.

Every site assessment starts with the site's contaminant profile, flow conditions, and discharge requirements — not a default product configuration. That consultative approach is what Abtech describes as building for Your Infrastructure and designing for Your Water Quality Goals.

Frequently Asked Questions: Stormwater Pits, Catch Basins, and Smart Sponge® Treatment

The following questions address what permit holders and operators most commonly ask when evaluating catch basin filtration for stormwater compliance.

Does the Ultra-Urban® Filter require modifications to an existing catch basin?

No. The Ultra-Urban® Filter is a drop-in insert designed to fit into existing catch basins without excavation, structural modification, or active power. It retrofits into the basin's existing geometry, which is why it is positioned as a retrofit-friendly compliance option for permit holders who need treatment without capital infrastructure projects.

What contaminants does Smart Sponge® target in a catch basin?

Smart Sponge® media formulations target PFAS, heavy metals, hydrocarbons and oil, bacteria, nutrients, sediment and TSS, and Total Organic Carbon (TOC). Because different sites present different contaminant mixes, media formulations can be selected and combined within a single Ultra-Urban® Filter insert to address multiple treatment objectives simultaneously.

How does Smart Sponge® handle high storm-event flow rates without bypassing?

Smart Sponge® media sustains flow rates up to 40 GPM per square foot with under 1 PSI of back pressure. That combination of high flow capacity and low back pressure means the insert treats water during storm events rather than allowing it to bypass the media — a critical performance requirement for catch basins in large paved catchments.

Will a catch basin insert satisfy my MS4 or NPDES permit requirements?

Smart Sponge® supports MS4 and NPDES compliance efforts by delivering measurable pollutant reduction at the catch basin. Whether a specific deployment satisfies a permit condition depends on site conditions, the applicable permit language, and the regulatory authority reviewing the program. Abtech provides field case studies and direct consultation to help permit holders build a defensible compliance record.

How do I determine which Smart Sponge® media formulation is right for my site?

Abtech's process starts with a Site Assessment — a direct consultation that evaluates your site's contaminant profile, flow conditions, and discharge requirements before recommending a media configuration. The company responds within one business day. You can initiate a Site Assessment through the Abtech Industries website.

Stormwater Pit and Catch Basin: How Passive Filtration Turns a Collection Point Into a Treatment Point