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ASCE EWRI International Low Impact Development Conference 2018 Kirstin Newfield, PhD Candidate, University of Toronto Supervisor: Dr. Jennifer Drake, University of Toronto
ASCE EWRI International Low Impact Development Conference 2018
Kirstin Newfield, PhD Candidate, University of Toronto
Supervisor: Dr. Jennifer Drake, University of Toronto
• Benefits and Barriers of Low Impact Development (LID)
• Autocase for Sites Software Overview
• Neighbourhood Scale Case Study – Creekside Village
• Results
• Costs and Benefits of Permeable Pavement at the Neighbourhood Scale
• Autocase for Sites in the Design Process
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vanishingpoint.ca
1.toronto.ca
oala.ca
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• Allows for infiltration on paved surfaces
• no infiltration
• partial infiltration
• full infiltration (soils with infiltration >15 mm/hr (0.6 inch/hr))
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• Runoff prevention
• Use of existing natural systems and hydrological processes
• Treat stormwater close to the source
• Water Quality
• Air Quality
• Multifunctional landscapes
• landscape based approach, community livability
• Educational Opportunities
• Energy
• Urban Heat Island Effect
• Biodiversity
• …
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Barriers Identified in Literature:
1. Economic
2. Legal
3. Regulatory
4. Education and Awareness
5. Organizational
6. Cultural
7. Technological
Actual and perceived
(Cote & Wolfe 2014; Earles et al. 2009; Roy et al. 2008)
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Cost Analysis
- LID cost is often assessed using a cost analysis that is limited to the
capital, operation and maintenance costs of the project.
Cost- Benefit Analysis
- analysis of costs and benefits over the lifespan of the project using the
net present value (NPV)
Triple Bottom Line – Cost-Benefit Analysis (TBL-CBA)
- analysis of all social, environmental and financial costs and benefits
over the lifespan of a project
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• Uncertainty in capital, operation and maintenance cost information
• The value of social and environmental factors is challenging to measure
• An economic analysis in the conceptualization phase of a project can
be cost-prohibitive
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• Triple Bottom Line- Cost Benefit Analysis Software
• Automated economic decision making
• Validated data and models valuing the costs and benefits of LID
• Applied to site specific projects at various scales to determine the net-present
value (NPV) of financial, social and environmental impacts.
• Notable Projects:
• City of Pittsburgh - Stormwater plan
• City of Toronto – public parks infrastructure
• San Francisco International Airport – proposed green roof
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Financial
• capital expenditures
• operations and maintenance costs
• replacement costs
• residual value of assets
Social
• flood risk
• heat island effect
• shadow wage
Environmental
• air pollution reduction by vegetation
• water quality
• carbon reduction by vegetation
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1. How does the TBL-CBA of a neighbourhood development using
traditional stormwater management techniques compare with a
neighbourhood development using permeable pavement?
2. How can a tool such as Autocase for Sites inform the design process?
3. What further considerations can be made to improve TBL-CBA for
sites?
Conduct a TBL-CBA using Autocase for Sites on two stormwater
management design scenarios
1. Traditional Stormwater Management
2. Low Impact Development
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Community
• 28 ha residential community
• 158 homes
• community buildings
• roadways, sidewalks
• parking areas
• environmentally and socially
focused design
(Figure Adapted from Creek Side Village n.d.)
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• stormwater discharged to a
surface municipal drain which
drains to Whitemans Creek
• Type A soils – Sand and gravel
• Infiltration Rate - 135 mm/hr
• Hydraulic Conductivity
7.8x10-4 cm/s
(Figure Adapted from Creek Side Village
n.d.: Whitemans Creek in red, Municipal
Drain in blue)
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Traditional Stormwater Management
• ~1,600 m3 stormwater management pond (SMP)
• designed for enhanced water quality protection level and 35% impervious cover (MOECC, 2003)
• 1,900 m underground piping
• SMP replaces a landscaped area
• discharged into municipal drain
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(Figure Adapted from Creek Side Village n.d.: SMP shown in red )
LID (proposed site design)
• All pavements (roadways, parking lots) as permeable interlocking concrete pavers (PICP)
• Full infiltration PICP
• Landscaped area to accommodate additional trees and shrubs
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(Figure Adapted from Creek Side Village n.d.: pavements in grey, landscaping in green)
16(Autocase, 2018)
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(Autocase, 2018)
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Design Scenario
Financial Environmental Social TBL
Traditional -$8,808,643 $74,674 $407,432 -$8,326,536
LID -$9,366,888 $134,543 $428,669 -$8,803,676
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-$8,000,000
-$7,000,000
-$6,000,000
-$5,000,000
-$4,000,000
-$3,000,000
-$2,000,000
-$1,000,000
$0
$1,000,000
Residual Value ofAssets
ReplacementCosts
Operations andMaintenance
CapitalExpenditures
Traditional Green Infrastructure
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$0
$50,000
$100,000
$150,000
$200,000
$250,000
$300,000
$350,000
Flood Risk Heat Island Effect Shadow Wage
Traditional Green Infrastructure
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-$150,000
-$100,000
-$50,000
$0
$50,000
$100,000
$150,000
Air PollutionReduced byVegetation Water Quality
Carbon Reductionby Vegetation
Carbon Emissionsfrom Concrete
Traditional Green Infrastructure
• Both traditional and LID design scenarios have a comparable TBL-CBA
• Permeable pavement is shown to be a viable alternative
• The most significant costs impacting the TBL are capital and operation
and maintenance costs
• Often analyzed in isolation using a simple cost analysis
• software tool can showcase how these costs can be offset by valuing
the benefits
• as research progresses with operation and maintenance practices and
LID becomes more widely used these costs may decrease over time
relative to traditional infrastructure.
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• Design Stage Considerations
• 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.
• Stakeholders
• 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.
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• More detailed inputs regarding water balance would highlight the site
specific benefits that LID can provide.
• 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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http://www.mycreeksidevillage.ca/
https://autocase.com/
• STEP and CH2M Hill Canada Ltd., 2016 (revised 2018). Inspection and
Maintenance Guide for Stormwater Management Ponds and
Constructed Wetlands.
• Center for Neighborhood Technology and American Rivers, 2010.
• Creek Side Village. "Creek Side Village." <www.mycreeksidevillage.ca>
(April 23, 2018].
• Impact Infrastructure. "Autocase for Sites." <https://autocase.com/>
(April 23, 2018].
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