Changes

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].

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 Guidance==

===Design Assumptions===

 

==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.

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.

Additional components include an underdrain to remove excess water and surface drains to deal with runoff flows in excess of design capacity.

==Life Cycle Costs==

==Life Cycle Costs==

Below are both the capital and life cycle costs of the three [[bioretention]] configuration practices 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.  

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.

 

Looking at the pie charts below for each configuration we can see that they are all relatively close to being the same cost with a variation of a few hundred dollars between each over both a 25 and 50-year time horizon. The percentage of the [[Bioretention: Full infiltration|Full Infitlration]] configuration is greater than the other two due to the lesser cost of the overall installation for material and Installation, (no underdrains, no gravel storage layer or impermeable membrane, etc.).

===25-Year life cycle cost break down===

===25-Year life cycle cost break down===

==Total Cost & Design Summary==

==Total Cost & Design Summary==

As previously discussed the three [[Permeable pavement]] configurations total cost summary vary greatly dependent on whether you want your feature to possess full infiltration, no infiltration, or partial infiltration. In short the most expensive of these options is the '''Permeable Pavement: No infiltration''' option ($187,356.33 vs. $168,085.10 - partial infiltration and $162,491.78 - full infiltration). The same can be said for construction + associated retrofit costs with each configuration design ($217,333.34 vs. $194,978.72 - partial infiltration and $188,490.47 - full infiltration). This configuration costs more than the other two predominantly due to the addition of an over 1,100m² [[Liner|Impermeable membrane]] (0.762 mm High Density Polyethylene-HDPE), which costs $24,181.47. This difference in price accounts for all three configurations possessing the exact same surface area footprint of 1,000m². As a reminder, it is important to understand your site's surrounding native soil infiltration rate to ensure you are selecting the appropriate design and if your site is located within a [[Source Water Protection#LID Site Considerations|WHPA]] or [[Pollution prevention|Pollution hotspot]], thus requiring a non-infiltration practice such as the aforementioned configuration of a permeable pavement feature. <br>

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).

 

A final note regarding the accuracy of the LCCT. A follow up sensitivity analysis study was conducted by CVC & STEP back in 2019 to test the tool's accuracy. The analysis took designs from 6 completed projects (4 [[bioretention]], 1 [[permeable pavement]], and 1 [[infiltration trench]]), and ran them through the tool comparing construction costing results from the LCCT to actual construction costs for the projects. The accuracy target set for the tool was plus-or-minus 30% of actual construction costs.<br>

'''The analysis found that the tool was on average (±14%) to 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>

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===

===Full Infiltration===

[[File:PICPchicago.jpg|thumb|500px||Permeable Interlocking Concrete Pavement (PICP) on a narrow road between buildings in Chicago (Source: ICPI)]]

[[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 PP Full Infil.PNG|700px]]<br>

[[File:Design Table PA Full Infil.PNG|700px]]<br>

</br>

</br>

===Partial Infiltration===

===Partial Infiltration===

[[File:Design Table PP Partial Infil.PNG|700px]]<br>

[[File:Design Table PA Partial Infil.PNG|700px]]<br>

</br>

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===Non-Infiltrating/filtration only===

===Non-Infiltrating/filtration only===

[[File:Design Table PP No Infil.PNG|700px]]<br>

[[File:Design Table PA No Infil.PNG|700px]]<br>

==References==

==References==