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Created page with "thumb|500px|Porous Asphalt in parking stalls (Source: EOR). {{TOClimit|2}} ==Overview== Porous Asphalt is an alterna..."
[[File:PorousAsphalt Stalls.png|thumb|500px|Porous Asphalt in parking stalls (Source: EOR).]]
{{TOClimit|2}}
==Overview==
[[Permeable pavement|Porous Asphalt]] is an alternative to traditional impervious pavements that allow stormwater to drain through them and into a storage reservoir below. Porous asphalt's performance and integrity is similar to that of other standard asphalt pavements. Porous asphalt contains air pockets, which are created during the development process of the paver due to the inclusion of less fines and [[sand]] content in comparison to traditional asphalt. The "air pcokets" or greater void spaces are what allow stormwater to infiltrate through the surface level to the underlying stone [[Reservoir aggregate|aggregate layer]] bed<ref>City of Toronto. 2017. Toronto Green Streets Technical Guidelines. Version 1.0. August, 2017. https://www.toronto.ca/legdocs/mmis/2017/pw/bgrd/backgroundfile-107515.pdf</ref>. The benefit of porous asphalt in comparison to some other permeable pavements is that it doesn't require third party, proprietary components, nor specialized paving equipment for installation<ref>Speight, J.G., 2016. Asphalt materials science and technology (pp. 437-474). Butterworth-Heinemann is. https://link.springer.com/article/10.1557/mrs.2016.267#article-info</ref>.
Depending on the native soil properties and site constraints, the system may be designed for full infiltration, partial infiltration, or as a non-infiltrating detention and filtration only practice. They can be used for low traffic roads, parking, driveways, and walk ways, and are ideal where space for other surface BMPs is limited. Permeable pavement types include:
*permeable interlocking pavers (concrete or composite materials)
*grid systems (concrete or composite materials)
*pervious concrete (poured-in-place or pre-cast)
*porous asphalt
*permeable articulating block/mat systems
For the sake of this page and associated costs/figures below the information found here relate to '''Porous Asphalt''', for costs and information associated with [[Permeable pavements: Life Cycle Costs|Permeable pavements click here]]. STEP conducted life cycle costs estimates for each of permeable pavements 3 design configurations which can be viewed below. To design your own life cycle cost estimates that can be adapted to fit your project budget and unique development needs access the updated [https://sustainabletechnologies.ca/lid-lcct/ LCCT Tool here].
===Design Assumptions===
Porous asphalt is ideal for sites with limited space and projects such as low traffic roads, parking lots, driveways and walkways. Components include: a porous asphalt surface, a stabilizer course, and a base layer for storage.
Additional components include an underdrain to remove excess water and surface drains to deal with runoff flows in excess of design capacity.
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, and vacuum sweeping annually. 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.
* Impervious drainage area to permeable surface area (I:P area) ratio of 1:1
* Default Stabilizing course/ Choker layer (19 mm dia. clear stone) depth of 50 millimetres.
* Default Asphalt depth of 110 millimetres.
* Default Stone resevoir (50 mm dia. clear stone) depth of 230 millimetres.
* A 150 mm diameter perforated underdrain pipe is included in Partial Infiltration and No Infiltration design configurations only.<br>
===Notes===
* Operation and maintenance cost estimates include removal of sediment from the catchbasin, by annual surface vacuum sweeping, repairing of potholes and assume no rehabilitation of the porous asphalt surface is required over the 50 year timeframe.
* 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.
* Unit costs are based on 2018 RSMeans standard union pricing.
* Additional costs associated with retrofit or redevelopment contents is assumed to be 16% higher than the cost for new (greenfield) development contexts.
** Retrofit construction cost estimates are included in the 'Costs Summary' section for comparison.<br>
==Construction Costs==
[[File:Construction Breakdown PA No Infil.PNG|thumb|right|400px|'''Construction Costs Per Unit Drainage Area (CAD$/m<sup>2</sup>) - No Infiltration Design, 25 mm Retention''']]
[[File:Construction Breakdown PA Full Infil.PNG|thumb|left|400px|'''Construction Costs Per Unit Drainage Area (CAD$/m<sup>2</sup>) - Full Infiltration Design, 25 mm Treatment''']]
[[File:Construction Breakdown PA Partial Infil.PNG|thumb|center|400px|'''Construction Costs Per Unit Drainage Area (CAD$/m<sup>2</sup>) - Partial Infiltration Design, 25 mm Retention''']]
<small>'''Note:''' Please click on each image to enlarge to view associated construction cost results.</small><br>
Above you can find a cost breakdown of a 1000m<sup>2</sup> in three different configurations:<br>
#[[Permeable pavements#Design|Non-infiltrating/filtration only Porous Asphalt]],
#[[Permeable pavements#Design|Partial infiltration Porous Asphalt]]
#[[Permeable pavements#Design|Full infiltration Porous Asphalt]]
As can be seen the greatest cost for this practice (regardless of configuration type) will be Material & Installation, which include costly components such as the, [[Liner|impermeable membrane/liner]], the [[underdrain]], the [[Permeable pavements#Foundation Aggregates|porous asphalt sub-base]] of 50mm [[clear stone]], the conventional asphalt base course (stone reservoir) of 230mm Granular A, [[clear stone|the 19mm Stabilizing course]] and the [[Permeable pavements: Specifications|asphalt (both conventional and permeable)]].
==Life Cycle Costs==
Below are both the capital and life cycle costs of the three [[permeable pavements|porous asphalt]] configurations over a 25- and 50-year time horizon based on a detailed assessment of local input costs, maintenance requirements, rehabilitation costs and design scenarios relevant to Canadian climates. The costs of maintenance and rehabilitation (Life cycle costs) are set at "Present Value" of these activities in 2022. The estimates of maintenance and rehabilitation (life cycle) costs represent net present values (NPV). Operation and maintenance costs are predicted to represent between 26 to 29% of total life cycle costs over the 25-year evaluation period, and increase to between 37 to 40% of total life cycle costs over the 50-year period, due to costs associated with increased surface vacuuming, restriping, repairing of potholes and cleaning out underground pipes (underdrain and overflow) to prevent [[clogging]] assumed to be continually required after 25 years of operation.
===25-Year life cycle cost break down===
[[File:25yr LCCT PA Full Infil.PNG|thumb|left|400px|'''Porous Asphalt: Full infiltration''']]
[[File:25yr LCCT PA No Infil.PNG|thumb|right|400px|'''Porous Asphalt: Non-infiltrating''']]
[[File:25yr LCCT PA Partial Infil.PNG|thumb|center|400px|'''Porous Asphalt: Partial infiltration''']]
<small>'''Note:''' Please click on each image to enlarge to view associated life cycle cost results.</small><br>
===50-Year life cycle cost break down===
[[File:50yr LCCT PA Full Infil.PNG|thumb|left|400px|'''Porous Asphalt: Full infiltration''']]
[[File:50yr LCCT PA No Infil.PNG|thumb|right|400px|'''Porous Asphalt: Non-infiltrating''']]
[[File:50yr LCCT PA Partial Infil.PNG|thumb|center|400px|'''Porous Asphalt: Partial infiltration''']]
<small>'''Note:''' Please click on each image to enlarge to view associated life cycle cost results.</small><br>
==Total Cost & Design Summary==
Total life cycle cost estimates for the three porous asphalt configurations vary substantially with the No Infiltration design being highest ($160,519.90), compared to the Partial Infiltration design ($138,144.27), and followed closely by the Full Infiltration design ($131,972.30).
It is notable that a sensitivity analysis was conducted in 2019 to compare construction cost estimates generated by the tool to actual costs of implemented projects. '''The analysis found that tool estimates were typically within ±14% of actual construction costs'''<ref>Credit Vally Conservation (CVC). 2019. Life-cycle costing tool 2019 update: sensitivity analysis. Credit Valley Conservation, Mississauga, Ontario. https://sustainabletechnologies.ca/app/uploads/2020/04/LCCT-Sensitivity-Analysis_March2020.pdf</ref>.
===Full Infiltration===
[[File:Kane-porous.jpg|thumb|800px|An example of installed porous asphalt in a designated biking lane, with curb cut inlets leading to adjacent bioswale features, located in the in the City of Gresham, Oregon (Source: Sightline Institute, 2012<ref>Sightline Institute, 2012. Surprisingly Ambitious Permeable Projects. Written by Lisa Stiffler. February 22, 2012. Accessed Dec. 16, 2022. https://www.sightline.org/2012/02/22/surprisingly-ambitious-permeable-projects/</ref>).]]
[[File:Design Table PA Full Infil.PNG|700px]]<br>
</br>
===Partial Infiltration===
[[File:Design Table PA Partial Infil.PNG|700px]]<br>
</br>
===Non-Infiltrating/filtration only===
[[File:Design Table PA No Infil.PNG|700px]]<br>
==References==
{{TOClimit|2}}
==Overview==
[[Permeable pavement|Porous Asphalt]] is an alternative to traditional impervious pavements that allow stormwater to drain through them and into a storage reservoir below. Porous asphalt's performance and integrity is similar to that of other standard asphalt pavements. Porous asphalt contains air pockets, which are created during the development process of the paver due to the inclusion of less fines and [[sand]] content in comparison to traditional asphalt. The "air pcokets" or greater void spaces are what allow stormwater to infiltrate through the surface level to the underlying stone [[Reservoir aggregate|aggregate layer]] bed<ref>City of Toronto. 2017. Toronto Green Streets Technical Guidelines. Version 1.0. August, 2017. https://www.toronto.ca/legdocs/mmis/2017/pw/bgrd/backgroundfile-107515.pdf</ref>. The benefit of porous asphalt in comparison to some other permeable pavements is that it doesn't require third party, proprietary components, nor specialized paving equipment for installation<ref>Speight, J.G., 2016. Asphalt materials science and technology (pp. 437-474). Butterworth-Heinemann is. https://link.springer.com/article/10.1557/mrs.2016.267#article-info</ref>.
Depending on the native soil properties and site constraints, the system may be designed for full infiltration, partial infiltration, or as a non-infiltrating detention and filtration only practice. They can be used for low traffic roads, parking, driveways, and walk ways, and are ideal where space for other surface BMPs is limited. Permeable pavement types include:
*permeable interlocking pavers (concrete or composite materials)
*grid systems (concrete or composite materials)
*pervious concrete (poured-in-place or pre-cast)
*porous asphalt
*permeable articulating block/mat systems
For the sake of this page and associated costs/figures below the information found here relate to '''Porous Asphalt''', for costs and information associated with [[Permeable pavements: Life Cycle Costs|Permeable pavements click here]]. STEP conducted life cycle costs estimates for each of permeable pavements 3 design configurations which can be viewed below. To design your own life cycle cost estimates that can be adapted to fit your project budget and unique development needs access the updated [https://sustainabletechnologies.ca/lid-lcct/ LCCT Tool here].
===Design Assumptions===
Porous asphalt is ideal for sites with limited space and projects such as low traffic roads, parking lots, driveways and walkways. Components include: a porous asphalt surface, a stabilizer course, and a base layer for storage.
Additional components include an underdrain to remove excess water and surface drains to deal with runoff flows in excess of design capacity.
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, and vacuum sweeping annually. 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.
* Impervious drainage area to permeable surface area (I:P area) ratio of 1:1
* Default Stabilizing course/ Choker layer (19 mm dia. clear stone) depth of 50 millimetres.
* Default Asphalt depth of 110 millimetres.
* Default Stone resevoir (50 mm dia. clear stone) depth of 230 millimetres.
* A 150 mm diameter perforated underdrain pipe is included in Partial Infiltration and No Infiltration design configurations only.<br>
===Notes===
* Operation and maintenance cost estimates include removal of sediment from the catchbasin, by annual surface vacuum sweeping, repairing of potholes and assume no rehabilitation of the porous asphalt surface is required over the 50 year timeframe.
* 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.
* Unit costs are based on 2018 RSMeans standard union pricing.
* Additional costs associated with retrofit or redevelopment contents is assumed to be 16% higher than the cost for new (greenfield) development contexts.
** Retrofit construction cost estimates are included in the 'Costs Summary' section for comparison.<br>
==Construction Costs==
[[File:Construction Breakdown PA No Infil.PNG|thumb|right|400px|'''Construction Costs Per Unit Drainage Area (CAD$/m<sup>2</sup>) - No Infiltration Design, 25 mm Retention''']]
[[File:Construction Breakdown PA Full Infil.PNG|thumb|left|400px|'''Construction Costs Per Unit Drainage Area (CAD$/m<sup>2</sup>) - Full Infiltration Design, 25 mm Treatment''']]
[[File:Construction Breakdown PA Partial Infil.PNG|thumb|center|400px|'''Construction Costs Per Unit Drainage Area (CAD$/m<sup>2</sup>) - Partial Infiltration Design, 25 mm Retention''']]
<small>'''Note:''' Please click on each image to enlarge to view associated construction cost results.</small><br>
Above you can find a cost breakdown of a 1000m<sup>2</sup> in three different configurations:<br>
#[[Permeable pavements#Design|Non-infiltrating/filtration only Porous Asphalt]],
#[[Permeable pavements#Design|Partial infiltration Porous Asphalt]]
#[[Permeable pavements#Design|Full infiltration Porous Asphalt]]
As can be seen the greatest cost for this practice (regardless of configuration type) will be Material & Installation, which include costly components such as the, [[Liner|impermeable membrane/liner]], the [[underdrain]], the [[Permeable pavements#Foundation Aggregates|porous asphalt sub-base]] of 50mm [[clear stone]], the conventional asphalt base course (stone reservoir) of 230mm Granular A, [[clear stone|the 19mm Stabilizing course]] and the [[Permeable pavements: Specifications|asphalt (both conventional and permeable)]].
==Life Cycle Costs==
Below are both the capital and life cycle costs of the three [[permeable pavements|porous asphalt]] configurations over a 25- and 50-year time horizon based on a detailed assessment of local input costs, maintenance requirements, rehabilitation costs and design scenarios relevant to Canadian climates. The costs of maintenance and rehabilitation (Life cycle costs) are set at "Present Value" of these activities in 2022. The estimates of maintenance and rehabilitation (life cycle) costs represent net present values (NPV). Operation and maintenance costs are predicted to represent between 26 to 29% of total life cycle costs over the 25-year evaluation period, and increase to between 37 to 40% of total life cycle costs over the 50-year period, due to costs associated with increased surface vacuuming, restriping, repairing of potholes and cleaning out underground pipes (underdrain and overflow) to prevent [[clogging]] assumed to be continually required after 25 years of operation.
===25-Year life cycle cost break down===
[[File:25yr LCCT PA Full Infil.PNG|thumb|left|400px|'''Porous Asphalt: Full infiltration''']]
[[File:25yr LCCT PA No Infil.PNG|thumb|right|400px|'''Porous Asphalt: Non-infiltrating''']]
[[File:25yr LCCT PA Partial Infil.PNG|thumb|center|400px|'''Porous Asphalt: Partial infiltration''']]
<small>'''Note:''' Please click on each image to enlarge to view associated life cycle cost results.</small><br>
===50-Year life cycle cost break down===
[[File:50yr LCCT PA Full Infil.PNG|thumb|left|400px|'''Porous Asphalt: Full infiltration''']]
[[File:50yr LCCT PA No Infil.PNG|thumb|right|400px|'''Porous Asphalt: Non-infiltrating''']]
[[File:50yr LCCT PA Partial Infil.PNG|thumb|center|400px|'''Porous Asphalt: Partial infiltration''']]
<small>'''Note:''' Please click on each image to enlarge to view associated life cycle cost results.</small><br>
==Total Cost & Design Summary==
Total life cycle cost estimates for the three porous asphalt configurations vary substantially with the No Infiltration design being highest ($160,519.90), compared to the Partial Infiltration design ($138,144.27), and followed closely by the Full Infiltration design ($131,972.30).
It is notable that a sensitivity analysis was conducted in 2019 to compare construction cost estimates generated by the tool to actual costs of implemented projects. '''The analysis found that tool estimates were typically within ±14% of actual construction costs'''<ref>Credit Vally Conservation (CVC). 2019. Life-cycle costing tool 2019 update: sensitivity analysis. Credit Valley Conservation, Mississauga, Ontario. https://sustainabletechnologies.ca/app/uploads/2020/04/LCCT-Sensitivity-Analysis_March2020.pdf</ref>.
===Full Infiltration===
[[File:Kane-porous.jpg|thumb|800px|An example of installed porous asphalt in a designated biking lane, with curb cut inlets leading to adjacent bioswale features, located in the in the City of Gresham, Oregon (Source: Sightline Institute, 2012<ref>Sightline Institute, 2012. Surprisingly Ambitious Permeable Projects. Written by Lisa Stiffler. February 22, 2012. Accessed Dec. 16, 2022. https://www.sightline.org/2012/02/22/surprisingly-ambitious-permeable-projects/</ref>).]]
[[File:Design Table PA Full Infil.PNG|700px]]<br>
</br>
===Partial Infiltration===
[[File:Design Table PA Partial Infil.PNG|700px]]<br>
</br>
===Non-Infiltrating/filtration only===
[[File:Design Table PA No Infil.PNG|700px]]<br>
==References==