Filtration: Gallery

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  Bioretention cell with a pre-treatment grass filter strip. Stormwater filters through mulch, filter media, and two sizes of clear stone before infiltrating into native soil.

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  LittaTrap catchbasin insert filters trash, debris, and sediment from runoff before it enters the catchbasin (Enviropod, 2022).

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  Stormwater planter allows for storage, filtration, and evapotranspiration of runoff (Philadelphia Water Department, 2025).

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.

a gently sloping, densely vegetated areas that treat runoff as sheet flow from adjacent impervious areas. They function by slowing runoff velocity and filtering out suspended sediment and associated pollutants, and by providing some infiltration into underlying soils.

a top dressing over vegetation beds that provides suppresses weeds and helps retain soil moisture in bioretention cells, stormwater planters and dry swales.

The engineered soil component of bioretention cell or dry swale designs, typically with a high rate of infiltration and designed to retain contaminants through filtration and adsorption to particles.

The natural ground material characteristic of or existing by virtue of geographic origin.

Box like underground concrete structure with openings in curb and gutter designed to collect runoff from streets and pavement.

Soil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls.

The portion of water precipitated onto a catchment area, which then flows as surface discharge from the catchment area past a specified point.

Water from rain, snow melt, or irrigation that flows over the land surface.

A vegetated practice that collects and treats stormwater through sedimentation and filtration. Contributions to water cycle/water balance are through evapotranspiration only; no infiltration.

The technique of removing pollutants from runoff as it infiltrates through the soil.

The quantity of water transpired (given off). Retained in plant tissues, and evaporated from plant tissues and surrounding soil surfaces. Quantitatively it is usually expressed in terms of depth of water per unit area during a specified period. e.g. mm/day

The combined loss of water to the atmosphere from land and water surfaces by evaporation and from plants by transpiration.