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Bioretention is an ideal technology for fitting functional vegetation into urban landscapes and treating runoff collected from nearby impervious surfaces.
* Designs include [[pretreatment]] through stone diaphragms at [[Curb cuts|curb inlets]]. Pretreatment through settling forebay and vegetated filter strip not included. Line 33:
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Permeable pavements: Life Cycle Costs (view source)
Revision as of 16:16, 14 December 2022
, 1 year ago→Design Guidance
==Design Guidance==
==Design Guidance==
Permeable pavers are ideal for sites with limited space and projects such as low traffic roads, parking lots, driveways and walkways. Components include: interlocking pavers, precast pervious slabs, cast in place surface, bedding course, and underground storage layer. Additional components include an underdrain to remove excess water and soil additives to enhance pollutant removal.
Components include: a 'filter bed' with [[filter media]], storage layer of [[reservoir aggregate]], [[planting]] and a finishing surface layer of [[mulch]] and/or [[stone]].
Additional components include an [[underdrain]] to remove excess water and soil additives to enhance [[Nutrients|pollutant removal]]. <br>
STEP recommendations:
*[[Bedding layer]] and [[Permeable pavements: Specifications|joint filler]] should consist of [[clear stone]] and [[gravel]] rather than [[sand]] to prevent [[clogging]].
*Granular materials should not be applied as anti-skid agents during winter because they can quickly clog the system.
*Winter maintenance practices should be limited to plowing, with de-icing salts applied sparingly.
*The slope of the permeable pavement surface should be at least 1% and no greater than 5%.
*The impervious land surround and draining onto the pavement should not exceed the area of the permeable pavement.
*Pervious surfaces should not drain onto the pavement.
*The storage layer must be sized to accommodate runoff from the pavement and any impermeable areas draining to it.<br>
Tool defaults based on STEP recommendations:
Tool defaults based on STEP recommendations:
* Maximum drainage area to surface area ratio of 20:1
* Maximum drainage area to surface area ratio of 1:1 (or 4:1 for roofs that contribute clean runoff to the practice)
* Default depth of 0.75 meters.
* Default Bedding depth of 50 millimeters.
* Default mulch depth of 75 millimeters.
* Default Base depth of 100 millimeters.
* An underdrain (minimum 200 mm perforated pipe) is only needed when native soil infiltration is less than 15 mm/hr or infiltration is precluded.
* An underdrain (minimum 150 mm perforated pipe) is only needed when native soil infiltration is less than 15 mm/hr or infiltration is precluded.
===Design Notes===
===Design Notes===
* The tool calculates costs for new designs and includes costs for contractor overhead and profit, material, delivery, labour, equipment (rental, operating and operator costs), hauling and disposal. Mobilization and demobilization costs not included. The tool adds 10% contingency and additional overhead.
* The tool calculates costs for new designs and includes costs for contractor overhead and profit, material, delivery, labour, equipment (rental, operating and operator costs), hauling and disposal. Mobilization and demobilization costs not included. The tool adds 10% contingency and additional overhead.
* Design and Engineering cost estimates are not calculated by the tool and must be supplied by the user.
* Design and Engineering cost estimates are not calculated by the tool and must be supplied by the user.
** Retrofit costs are included in the 'Costs Summary' section and can be added to the Total Construction Cost for increased accuracy.<br>
** Retrofit costs are included in the 'Costs Summary' section and can be added to the Total Construction Cost for increased accuracy.<br>
<small>'''Note''': Bioretention (all 3 design scenarios): Includes pretreatment sump at inlet and assumes that rehabilitation of filter media bed is performed at 25 years.</small>
<small>'''Note''': Permeable Pavements (all 3 design scenarios): Assumes that replacement of pavers occurs at 8 years, and a full rehabilitation of the practice is performed at 30 years.</small>
==Construction Costs==
==Construction Costs==