Design Specifications

Design Specification No 1: Rooftop Disconnection
Downspout disconnect into grassy area

This strategy involves managing runoff close to its source by intercepting, infiltrating, filtering, treating or reusing it as it moves from the impervious surface to the drainage system.
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Design Specification No 2: Sheet Flow to a Vegetated Filter Space or Conserved Open Space
Stormwater Filter

Filter strips are vegetated areas that treat sheet flow delivered from adjacent impervious and managed turf areas by slowing runoff velocities and allowing sediment and attached pollutants to settle and/or be filtered by the vegetation.
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Design Specification No 3: Grass Channels
Grass Channel

Grass channels can provide a modest amount of runoff filtering and volume attenuation within the stormwater conveyance system resulting in the delivery of less runoff and pollutants than a traditional system of curb and gutter, storm drain inlets and pipes.
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Design Specification No 4: Soil Compost Amendment

Soil amendments can reduce the generation of runoff from compacted urban lawns and may also be used to enhance the runoff reduction performance of downspout disconnections, grass channels, and filter strips.
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Design Specification No 5: Vegetated Roof

Vegetated roofs are alternative roof surfaces that typically consist of waterproofing and drainage materials and an engineered growing media that is designed to support plant growth.
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Design Specification No 6: Rainwater Harvesting
Underground Cistern

Rainwater that falls on a rooftop is collected and conveyed into an above- or below-ground storage tank where it can be used for non-potable water uses and on-site stormwater disposal/infiltration.
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Design Specification No 7: Permeable Pavement

Permeable pavement is typically designed to treat stormwater that falls on the actual pavement surface area, but it may also be used to accept run-on from small adjacent impervious areas, such as impermeable driving lanes or rooftops.
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Design Specification No 8: Infiltration Practice

Infiltration practices use temporary surface or underground storage to allow incoming stormwater runoff to exfiltrate into underlying soils, allowing for a very high runoff volume reduction capability.
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Design Specification No 9: Bioretention

Bioretention creates a good environment for runoff reduction, filtration, biological uptake, and microbial activity, and provides high pollutant removal; bioretention can become an attractive landscaping feature with high amenity value and community acceptance.
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Design Specification No 10: Dry Swales
Dry Swale

Dry swales are essentially bioretention cells that are shallower, configured as linear channels, and covered with turf or other surface material (other than mulch and ornamental plants).
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Design Specification No 11: Wet Swale
Vegetated wet swale

Wet swales can provide runoff filtering and treatment within the conveyance system and are a cross between a wetland and a swale.
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Design Specification No 12: Filtering Practices
Stormwater Filter

Stormwater filters depend mainly on physical treatment mechanisms to remove pollutants from stormwater runoff, including gravitational settling in the sedimentation chamber, straining at the top of the filter bed, and filtration and adsorption onto the filter media.
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Design Specification No 13: Constructed Wetlands

Constructed wetlands are shallow depressions that receive stormwater inputs for water quality treatment, are typically less than 1 foot deep, and possess variable microtopography to promote dense and diverse wetland cover.
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Design Specification No 14: Wet Pond
Wet Pond

Wet ponds consist of a permanent pool of standing water that promotes a better environment for gravitational settling, biological uptake and microbial activity.
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Design Specification No 15: Extended Detention Pond
Extended Detention Pond

An extended Detention pond relies on 12 to 24 hour detention of stormwater runoff after each rain event; an under-sized outlet structure restricts stormwater flow so it backs up and is stored within the basin.
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