The Costs and Benefits of Permeable Pavement at the Neighbourhood Scale

The presentation of research into permeable pavement using Autocase marked the end of Kirstin Newfield’s work with us. Kirstin is a PhD Candidate at the University of Toronto. We were sorry to see her go but happy to see her work presented.

The Costs and Benefits of Permeable Pavement at the Neighbourhood Scale – Using Autocase for Sites” was presented recently, at the ASCE EWRI International Low Impact Development Conference 2018 by Kirstin Newfield’s supervisor: Dr. Jennifer Drake of the University of Toronto.

Permeable pavement allows for infiltration on paved surfaces. Autocase can model the infiltration benefits of this low impact development (LID) feature. I have seen examples in the city of Berkeley (left) near the Berkeley High School and their municipal offices. The better stormwater drainage, a smaller carbon footprint, and less maintenance than traditional asphalt made it attractive there. I’ve also seen it at the Credit Valley Conservation parking lot in Toronto (below).

Kirstin’s work looked at a case study at Creek Side Village in Ontario, Canada. This was a larger scale project. The community is a 28 ha, 158 homes and community buildings site with roadways, sidewalks, parking areas and an environmentally and socially focused design.

In particular, all pavements (roadways, parking lots) as permeable interlocking concrete pavers (PICP). The full infiltration PICP was accompanied by landscaped area to accommodate
additional trees and shrubs.

During the design Autocase’s flexibility in the software allows for use throughout the various stages of design. The results of this TBL-CBA demonstrate room for optimization in the design of the LID scenario. This can be beneficial in the early stages of design to compare alternatives.

A TBL-CBA report can inform the discussion amongst the various stakeholders (developers, owners, municipalities, regulatory bodies…). The breakdown of the various costs and benefits allows for various stakeholders to understand how the site design impacts their interests.

Kirstin’s research highlighted some improvements we can make in Autocase, some of which are already underway. She found that more detailed inputs regarding water balance would highlight the site specific benefits that LID can provide. Some examples:

  • Treatment Train benefits of LID
  • Expanding the financial, social and environmental values that the TBL-CBA models would help build the case for LID.
    • Examples include: replenishing the groundwater table through infiltration, accessibility benefits of permeable pavement, impacts of stormwater discharge to a nearby watercourse.
    • Autocase is continually developing the software and including new models as they become available including groundwater recharge and a more detailed pollutant loading model.
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