Monday, December 9, 2019

Maintaining Water Quality Protection After Development is Complete

Structural Best Management Practices

Dry Extended Detention Pond

Dry extended detention ponds or dry ponds and detention basins are the most widely applicable stormwater management practices. They are basins whose outlets have been designed to detain the stormwater runoff from a water quality design storm for some minimum time to allow particles and associated pollutants to settle.

Wet Ponds

Wet ponds are widely applicable stormwater management practices.  Wet ponds or stormwater ponds and retention ponds are constructed basins that have a permanent pool of water throughout the year (or through the wet season). Ponds treat incoming stormwater runoff by settling and algae uptake. Wet ponds are among the most cost effective and widely used stormwater practices.

Infiltration Basin

An infiltration basin is a shallow impoundment, which is designed to infiltrate stormwater into the ground water. Infiltration basins can be challenging to apply on many sites because of soils requirements.

Infiltration Trench

An infiltration trench is a rock filled trench with no outlet that receives stormwater runoff. The runoff is stored in the void space between the stones and infiltrates through the bottom and into the soil matrix.

Porous Pavement

Porous pavement is a permeable surface with an underlying stone reservoir to temporarily store surface runoff before it infiltrates into the subsoil. The ideal application for porous pavement is to treat low-traffic or overflow parking areas.

Bioretention

Bioretention areas are landscaping features adapted to provide on-site treatment of stormwater runoff. Surface runoff is directed into shallow, landscaped depressions. These depressions act as a filtration system and pollutant removal.

Sand and Organic Filters

Sand filters have proven effective in removing several common pollutants from stormwater runoff. Sand filters generally control stormwater quality, providing very limited flow rate control. A typical sand filter system consists of two or three chambers or basins. The first is the sedimentation chamber, which removes floatables and heavy sediments. The second is the filtration chamber, which removes additional pollutants by filtering the runoff through a sand bed. The third is a discharge chamber.

Stormwater Wetland

Stormwater wetlands 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 within the practice

Grassed Swales

As stormwater runoff flows through these channels, it is treated through filtering by the vegetation in the channel, filtering through a subsoil matrix, and/or infiltration into the underlying soils. Variations of the grassed swale include the grassed channel, dry swale, and wet swale.

Other Structural Best Management Practices Include:

  • Grassed filter strip
  • Catch basin inserts
  • Manufactured products for stormwater inlets

Non-Structural Best Management Practices

Buffer Zones – An aquatic buffer is an area along a shoreline, wetland, or stream where development is restricted or prohibited. Buffers will separate new construction from its encroachment into stream, lakes, or wetland areas.

Open Space Design – Open space design and its comparison to the conventional subdivision. Open space design can reduce impervious cover, stormwater pollutants, construction costs, grading, and loss of natural areas.

Other Non-Structural Best Management Practices Include:

  • Conservation easements
  • Infrastructure planning
  • Eliminating curb and gutters
  • Green parking
  • Zoning
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