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====STEP recommendations:==== Line 25:
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* Default Bedding depth of 50 millimeters. * Default Base depth of 100 millimeters. * 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=== <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>
Permeable pavements: Life Cycle Costs (view source)
Revision as of 17:07, 15 December 2022
, 2 years ago→Design Guidance
For the sake of this page and associated costs/figures below the information found here relate to '''Permeable Pavers''', for costs and information associated with [[LID LCCT: Porous Asphalt|Porous Asphalt click here]]. STEP has prepared life cycle costs estimates for each design configuration, based on a 2,000 m<sup>2</sup> asphalt drainage area, runoff control target of 25 mm depth and 72 hour drainage period, for comparison which can be viewed below. To generate your own life cycle cost estimates customized to the development context, design criteria, and constraints applicable to your site, access the updated [https://sustainabletechnologies.ca/lid-lcct/ LID Life Cycle Costing Tool (LCCT) here].
For the sake of this page and associated costs/figures below the information found here relate to '''Permeable Pavers''', for costs and information associated with [[LID LCCT: Porous Asphalt|Porous Asphalt click here]]. STEP has prepared life cycle costs estimates for each design configuration, based on a 2,000 m<sup>2</sup> asphalt drainage area, runoff control target of 25 mm depth and 72 hour drainage period, for comparison which can be viewed below. To generate your own life cycle cost estimates customized to the development context, design criteria, and constraints applicable to your site, access the updated [https://sustainabletechnologies.ca/lid-lcct/ LID Life Cycle Costing Tool (LCCT) here].
==Design Guidance==
==Design Assumptions==
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.
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.
===STEP's LCCT Assumptions:===
Design and operation and maintenance program assumptions used to generate cost estimates are based on tool default values and the following STEP recommendations:
*Native soil infiltration rates for Full, Partial and No Infiltration Design scenarios were assumed to be 20 mm/h, 10 mm/h and 2 mm/h, respectively, and a safety factor of 2.5 was applied to calculate the design infiltration rate.
*Operation and maintenance (O&M) cost estimates assume annual inspections, removal of trash and debris twice a year, removal of sediment from pretreatment structures annually, and removal of weeds twice a year (where applicable). Verification inspections are included every 5 years to confirm adequate maintenance, and every 15 years to confirm adequate drainage performance through in-situ surface infiltration rate testing (where applicable).
* Maximum impervious drainage area to permeable surface area (I:P area) ratio of 1:1 (or 4:1 for roofs that contribute clean runoff to the practice)
* Default Bedding depth of 50 millimeters.
* Default Base depth of 100 millimeters.
* Default Sub-base depth (50 mm dia clear stone) of 200 millimeters.
* An underdrain (minimum 150 mm perforated pipe) is included in Partial Infiltration and No Infiltration design configurations only.
*[[Bedding layer]] and [[Permeable pavements: Specifications|joint filler]] should consist of [[clear stone]] and [[gravel]] rather than [[sand]] to prevent [[clogging]].
*[[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.
*Granular materials should not be applied as anti-skid agents during [[winter]] because they can quickly clog the system.
*The [[Permeable pavements: Specifications|storage layer]] must be [[Permeable pavements: Sizing|sized to accommodate runoff]] from the pavement and any impermeable areas draining to it.<br>
*The [[Permeable pavements: Specifications|storage layer]] must be [[Permeable pavements: Sizing|sized to accommodate runoff]] from the pavement and any impermeable areas draining to it.<br>
====Tool defaults based on STEP recommendations:====
===Notes===
* Maximum drainage area to surface area ratio of 1:1 (or 4:1 for roofs that contribute clean runoff to the practice)
* Operation and maintenance cost estimates assume replacement of severely degraded/failing pavers after the first 8 years of operation.
* The tool calculates costs for new (greenfield) development contexts and includes costs for contractor overhead and profit, material, delivery, labour, equipment (rental, operating and operator costs), hauling and disposal.
** Land value and equipment mobilization and demobilization costs are not included, assuming BMP construction is part of overall development site construction.
** Design and Engineering cost estimates are not calculated by the tool and must be supplied by the user.
** The tool adds 10% contingency and additional overhead as default.
* All cost estimates are in Canadian dollars and represent the net present value (NPV) as the tool takes into account average annual interest and discount rates over the 25 and 50 year operating life cycle periods.
* 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.
* Unit costs are based on 2018 RSMeans standard union pricing.
* Design and Engineering cost estimates are not calculated by the tool and must be supplied by the user.
* Additional costs associated with retrofit or redevelopment contents is assumed to be 16% higher than the cost for new (greenfield) development contexts.
* Unit costs are based on 2018 pricing; the tool automatically adds inflation. See the Assumptions sheet in the tool for further details.
** Retrofit construction cost estimates are included in the 'Costs Summary' section for comparison.<br>
* The cost of retrofitting is ~16% higher than the cost of new construction.
** Retrofit costs are included in the 'Costs Summary' section and can be added to the Total Construction Cost for increased accuracy.<br>
==Construction Costs==
==Construction Costs==