Green Infrastructure Cost - Ontario Tender Costs Support Economic Analysis for Master Plans, Asset Management, Retrofit Strategies

Numerous green infrastructure, low impact development (LID) stormwater best management practices (BMPs), projects have been implemented in Ontario and across North America. To support planning studies and strategy development, capital costs for implementation are required.  The following table summarizes recent project costs, based largely in Ontario.

The average cost per treated hectare is $530,000 (total project costs are weighted by total project area).  The design volume for the majority of the projects is not available.

Ontario (and Alberta) Green Infrastructure Costs

The cost for these LID measures varies according to the type of feature as shown on the following chart that plots cost vs. service area (drainage catchment controlled).  Projects were grouped by type where possible, although some projects may incorporate more than one type in a treatment train.  The chart illustrates that Infiltration Trenches have the lowest cost per drainage area served. Rain Garden & Bioswales have the highest cost.

Ontario (and Alberta) Green Infrastructure Costs by Type

Previous posts summarized costs from programs in the US.  The summary of 39 Ontario (and a couple Alberta) projects represent a total capital cost of $19.2M and a total service area of 36.2 hectares.  This area is comparable to the area of costed green infrastructure projects in the US EPA International BMP database.

The following table compares cost by LID type for three sources, the Philadelphia CSO control program, the ES UPA BMP database, and the compiled Ontario (and Alberta) tenders noted above.  The Philadelphia and the US EPA data both include design storage volume that may be considered for achieving different types of stormwater management goals (i.e., levels of service / performance outcomes).

Green Infrastructure Costs by Type and Design Volume - Philadelphia CSO Control Program, US EPA BMP Database, and Ontario (and Alberta) Completed Projects

Some key observations are that porous/permeable pavement has a relatively high cost per drainage area ($/ha), however the cost per storage volume is relatively low for the US EPA datasets - this warrants further review.  The Ontario/Alberta porous/permeable pavement costs per area are also relatively high, compared to other types.  Just like Ontario/Alberta data, Philadelphia and US EA data shows lowest cost per hectare for infiltration/exfiltration projects.  The infiltration/exfiltration cost per storage volume was relatively low for both the US EPA and Philadelphia datasets.

The Philadelphia green infrastructure projects achieve a high volume, equivalent to 38.9 mm over the catchment area draining to it.  In contrast, the US EPA storage volumes are equivalent to only 6.6 mm.  The Philadelphia projects are sized for 1-2 inches of storage to achieve CSO control.  In contrast the US EPA projects are sized to achieve other benefits, such as watershed protection.

While the Philadelphia cost per area is highest at $857,000 per hectare, which is 4.1 times the US EPA database cost of only $208,000 per hectare, the unit cost per storage is in fact less.  The Philadelphia unit cost is $22,000 per hectare-mm.  The US EPA cost is $32,000 per hectare-mm, reflecting lower cost efficiency for smaller installations perhaps.

Using these unit costs one can estimate the budget required to retrofit green infrastructure into older urban areas to improve stormwater management.  In Ontario, the urban area built by 1966 has been estimated to be 110,000 hectares (Ducks Unlimited mapping), and by year 2000 to be 852,000 hectares (provincial SOLRIS land use mapping v2).  Assuming that 200,000 hectares require significant storage to achieve flood control in older communities, the retrofit cost would be $171 billion, applying the $857,000/hectare unit cost.  Or to provide improved water quality and water balance controls to the year 2000 urban area, the retrofit cost would be $177 billion, applying the $208,000/hectare unit cost.  Both of those costs represent considerable sums, given the Ontario stormwater infrastructure deficit of about $6.8 billion - that is the retrofit cost would be over 25 times that current deficit.  Given that, a strategic approach to retrofitting older communities is required, including prioritization of retrofit areas, implementing on higher-performance sites (e.g., permeable soils), implementing on highest risk tributaries (sensitive habitat, infrastructure or property risks), and considering the most cost effective measures, e.g., higher volume/centralized facilities that exhibit lower unit costs for storage, and feature types with lowest unit costs (i.e., infiltration/exfiltration facilities, and (to be confirmed) porous/permeable pavement).  The operation and maintenance costs associated with porous/permeable pavement should also be considered in the development of a retrofit strategy (i.e., consider full lifecycle costs including both capital and operating costs).

Investing in Canada's Future: The Cost of Climate Adaptation - does infrastructure spending recommended in a new report for by IBC for FCM make sense?

Investing in Canada's Future: The Cost of Climate Adaptation
Investing in Canada's Future: The Cost of Climate Adaptation,
Report by IBC and FCM, September 2019 
A new report by the Insurance Bureau of Canada attempts to answer an important question: How much should we invest in adaptation measures to prevent effects of climate change?

The report summary "Investing in Canada's Future: The Cost of Climate Adaptation" (link) suggests the following:

"The analysis determined that an average annual investment in municipal infrastructure and local adaptation measures of $5.3 billion is needed to adapt to climate change. In national terms, this represents an annual expenditure of 0.26% of GDP."

"Flood, erosion and permafrost melt are associated with the highest cost to GDP ratios at 1.25, 0.12 and 0.37, respectively. These climate risks require the greatest investment in adaptation."

The infographic summary (link) suggests that " the benefits of investing in community adaptation and resilience outweigh the cost of such investments by a ratio of 6 to 1".

Let's review this in terms of mitigation of flood damages.

The annual expected insured losses from hydrologic and meteorologic events in Canada is $0.7B based on Munich Re data.  Overall losses are $1.27B considering Munich Re ratios.  Over 100 years that some infrastructure lasts, that is $127B in losses, some that can be effectively mitigated or deferred.  If there is a 6:1 benefit:cost ratio to adaptation efforts, then spending $127B/6 = $21.2B would be the cost of the adaptation program to 'break even' (let's assume that is the capital cost and not operation and maintenance).

The IBC FCM study suggests spending of $5.3B per year - a lot more than the 'break even' number -and notes "What is needed now is an ambitious and long-term investment plan for disaster mitigation and adaptation charted along a time frame of not year-to-year, but for the next twenty years or longer."

Let's look at the numbers.

If we invest $5.3B per year for 20 years, that is $106B. So that is a benefit:cost ratio of $127B:$106B or 1:2:1.  If we invest $5.3B a year for 25 years, the cost exceeds the benefits.  That investment is a lot higher than what we would expect if we achieved a 6:1 benefit:cost ratio, spending only $21.2B.

If we consider that losses cannot be completely deferred with adaptation (as it is rarely 100% effective, and there may always be events that exceed design capacity leaving residual damages, and overall losses cannot be completely deferred), the potential benefits over 100 years may be only $70B, assuming all insured losses can be mitigated.  That means spending $5.3B a year for 20 years, or $106B will cost more than the benefits.

This should be carefully reviewed.  The value of all municipal storm and wastewater and bridge infrastructure in Canada is $418 B (see my 2018 CWWA presentation here). So investing $106B, or 25% of the value of all that infrastructure value is a lot.  Some municipality flood mitigation programs has been estimated at only 6% of asset value.

Setting investment levels appropriately is important and further analysis is needed.  It would also be worthwhile distinguishing between the cost to address today's infrastructure capacity and land use planning risks and future risks.  Much of Canada's current $0.7B in damages is due to existing level of service deficiencies and not future climate effects.


In a previous study Green Analytics acknowledged the difference between damages due to economic growth and those due to future climate effects.  It would be worth looking at effects of future growth on damages and consider those in assessing infrastructure investment requirements.

Extreme Rainfall Trends in Canada - Engineering Climate Datasets for Long Term Climate Stations Show Increases and Decreases

Environment and Climate Change Canada's Engineering Climate Datasets includes trends in observed annual maximum rainfall over durations of 5 minutes to 24 hours.  Version 3.00 of the data was released in early 2019.  The following table shows trend direction and significance for stations across Canada.  It represents 3993 station-years of data, with an average of 47 years of data at 85 stations.
Some observations:

- out of 85 stations with trends over 9 durations, 7.9% of trends are statistically significant increases

- 1.8% of trends are statistically significant decreases

- the total of significant increases and decreases (7.9+1.8=9.7%) is mostly explained by chance (5% could be explained by random chance, due to the natural variability of the data)

- there are more increases than decreases with the exception of Ontario where southern Ontario has more decreases than increases, while northern Ontario has more decreases

- southern Ontario has 50% more significant decreases than increases

- Alberta is almost even with increases and decreases, and has no statistically significant increases, and just one significant decrease

- statistically significant increases are more prevalent for long durations over 1 hour (10%), than for short durations of 1 hour or less (6.4%) .. so significant increases for short durations are slightly above the % explained by randomness in the natural variability, in contrast, long durations have more significant increases than would be expected by chance

- statistically significant decreases are more prevalent for short durations of 1 hour or less (2.1%), than for long durations of over 1 hour (1.5%)

A review of these trends based on earlier v2.30 datasets, specifically stations with 20 years of record between 1965 and 2005, was presented by Shephard et. al in Atmosphere-Ocean in 2014:

"Summary statistics in Table 6 show that for all durations fewer than 5.6% and 3.4% of the total number of stations have significant increasing and decreasing trends in the AMS amounts, respectively. The highest percentage of stations with significant trends from any duration is 7.8%
(5.6% + 2.2%) for the 24-hour duration, which is close to the nominal 5% significance level. Based on this IDF single station analysis, and the more general single station climate results from the 1965–2005 period presented in Section 4a, we conclude that the annual maximum short duration rainfall values across Canada typically do not show a significant trend. Thus, for most of the single station IDF stations across Canada there is no evidence indicating that the stationarity assumption used in the traditional national EC IDF calculations has been violated. These results are not unexpected given the typical high variability and relatively short time series of the extreme short-duration rainfall observations."

Therefore Environment and Climate Change Canada find 'no evidence' that data used in IDF calculations is changing (values are stationary), and significant trends are generally no more than the natural variability would suggest.

Assessing the Damage. CBC Ombudsman Finds Wrong Flood Damage Values Reported, Notes "broader concern that there is a pattern of imprecision in CBC’s coverage relating to flood events"

The CBC Ombudsman has found violations in the CBC’s Journalistic Standards and Practices related to an April 11, 2019 article entitled "Canada's building code is getting a climate change rewrite. Is your home ready?" (link).

The violations relate to publishing the wrong value for flood damages resulting from a Toronto August 2018 storm, and failing to note corrections to an article.

The CBC has always been very responsive to feedback on extreme weather reporting, including on the frequency of extreme events.  In January 2019, the Ombudsman also found violations related to reporting of more frequent extreme rainfall events (i.e., 100-year storms) - corrections to a couple stories were required.  Those Ombudsman's findings are noted in a previous post.  Other CBC story corrections have been made since 2015, again relating to storm frequency and the causes of flooding, and are noted in this previous post.

The new Ombudsman findings are described here.

While the complaint surrounding the April 11, 2019 article is related to a single storm, the Ombudsman noted that there is a broader issue stating:

"I have a broader concern that there is a pattern of imprecision in CBC’s coverage relating to flood events."

This comment is based on the fact that the cited average flooded basement claim or payout was $43,000 was really based on an extreme 2013 flood event in Toronto - not an average at all - yet it has been repeated over and over by the media including CBC.

A previous post shows how this value started (as $40,000 back in 2017) and how it has been expanded to cover the whole country.  It has been used in Intact Centre on Climate Adaptation's infographics as well:

Intact Financial Corporation's website refers to the $43,000 value too:

Global News. The Globe and Mail. Canadian Underwriter. TVO's The Agenda. All repeat the incorrect $43,000 value. Only CBC has been keen enough to entertain a review and make corrections to the record.

The full review is noted below for reference

Assessing the Damage
  • Sep 20, 2019
    CBC reported that concerns about climate change are causing government to re-think the rules for construction of buildings and infrastructure. Complainant Robert Muir took exception to several details in the online article. Among them was an estimate of damage caused by one particular storm, which led to this review about expert sources, and the importance of precision in journalism.


    You listed four deficiencies in the original version of a story headlined Canada's building code is getting a climate change rewrite. Is your home ready? which was published on April 11, 2019.
    The article concerned various proposals to create tougher standards for the construction of buildings and infrastructure projects in Canada. It explained to readers that governments are considering these changes in order to mitigate the expected impact of a changing climate.
    Two of your points prompted CBC News to make amendments to the article. One concerned wording that implied that predicted changes in extreme rainfall events had already been demonstrated. The other concerned the use of incorrect terminology to describe a backwater valve. Many homeowners will recognize this device which can decrease the risk of a sewage backup in their home.
    Your third point suggested the article should have more fully addressed the cost effectiveness of the various proposals.  In response, CBC News explained that this was outside of the scope of this particular article. 
    You were satisfied that those three points were properly addressed. However, on your fourth point, you requested a review. The remaining dispute relates to a section of the article which included an interview with Natalia Moudrak, Director of Climate Resilience at the University of Waterloo's Intact Centre. At one point she discussed the amount of damage caused to homes by flooding in Toronto.
    Here is the relevant excerpt of the article:
    While architects and construction workers grapple with reducing emissions from large buildings, average Canadians will face other problems. 
    "Flooding is the biggest challenge" linked to climate change for most homeowners, said Natalia Moudrak, director of climate resilience at the University of Waterloo's Intact Centre. 
    And there are measures homeowners can take now to safe address flooding.
    If a homeowner has a pump to get water out of a basement, "it's important to install a backup generator," she said. Widespread flooding often leads to power outages, leaving regular pumps useless when they're most needed.
    Homeowners can also take simple steps to elevate valuables, like expensive electronics, off their basement floor or put items in plastic or steel containers in case water does creep in, Moudrak said. 
    To prevent sewage from flowing into your home during a flood, David Foster, a spokesperson for the Canadian Home Builders' Association, recommends installing a backwater valve, a mechanical backflow prevention device linked to the plumbing and designed to allow water from sewer drains to only flow away from the home.
    "There is not a lot of cost involved in that, it just involves changing the way things are done," said Foster, who has consulted with the government on the new code. 
    When constructing a new home, installing a backwater valve costs roughly $400, Moudrak said. When retrofitting an existing home, it usually costs about $3,000. But municipalities often offer subsidies to help offset that expense.
    The problem, she said, is most people don't know about them.
    Only six per cent of Toronto homeowners took advantage of the city's flood resilience subsidy program, she said. When floods hit the city last year, she said the average cost to affected homeowners was $43,000.
    The sentence at the heart of your complaint is the very final one. You wrote that the $43,000 figure was “misstated”. It reflected the Intact Centre’s Toronto 2013 Flood Report, not the 2018 one (i.e. - the article states “last year”). You also suspected that the calculations of the estimate are based on studies done in the United States by the National Flood Insurance Program.
    You said more accurate numbers could be obtained from the CatIQ database, which you describe as “the definitive source for compiled flood damages from Canada’s insurance companies.” Based on the number of claims and total value of payouts from the 2018 storm, you suggested that a more accurate number was $18,509 rather than $43,000. You wrote:
    I believe that it is important to clarify given the fact that urban flooding is a significant issue, the costs of risk reduction are immense, and sound economic data and analysis is required to make evidence-based decisions on damage reduction management strategies. Flood damage data is a key piece of this economic data and many municipalities have cited the $43,000 value in federal infrastructure grant applications, which may not reflect actual damages, and could therefore adversely affect how scarce resources are allocated to address an important infrastructure challenge. 


    Paul Hambleton, the Director of Journalistic Standards and Practices, responded on behalf of CBC News:
    To be clear, the story quoted Natalia Moudrak, director of climate resilience at the University of Waterloo’s Intact Centre on Climate Adaptation: “When floods hit [Toronto] last year, she said the average cost to affected home owners was $43,000”. That information is also included in Weathering the Storm: Developing a Canadian Standard for Flood-Resilience in Existing Communities, a report published in January and co-authored by Ms. Moudrak.
    In a footnote, the report attributes that estimate to the Insurance Bureau of Canada (IBC) “based on Toronto flooding in 2013”. However, you wrote, the actual source is FEMA’s National Flood Insurance Program (NFIP) cited in a July, 2012 story in Forbes. The story cites the interactive “Cost of Flooding” found on the NFIP page as estimating nearly $40,000 damage to a 2,000 sq. ft. home after a 6-inch flood.   
    It’s interesting to note that in looking at it now, almost seven years later, “Cost of Flooding” estimates damage of a little over $20,000 for a 1,000 sq. ft. home and about $52,000 to a 2,500 sq. ft. one-storey home. (There was no estimate for 2,000 sq. ft. home).
    It’s pretty clear that there is a range of estimates and, it seems, little public information about how those numbers were reached. But you have touched on an interesting issue here.
    On one level, while reporters can tell us what they see and hear, there are many things that they don’t witness or can’t know. In those instances they attribute the information. That way, readers know the source and can make their own judgment about its reliability. In this instance, we attributed the information to Ms. Moudrak, identifying her position and the organization she works for.


    In a perfect world journalists would have expertise in every subject they cover. In the real world, many reporters, along with their editors, are generalists who strive to learn as much as they can in a short time so they can report faithfully and accurately on the subject at hand. 
    This means that there are times where they reasonably rely on subject experts to explain how something works, why something happens, or what might happen next. It might be a doctor, a realtor, or a marketing executive. In each case, the reporter looks to use their expertise as a way to improve the story with informed insights. 
    In such situations reporters willingly put themselves at the mercy of the expert’s knowledge. If an expert were to give bad information, CBC’s Journalistic Standards and Practices doesn’t let either of them off the hook. There is a section called “Responsibility and Accountability Related to Interviews” which reads as follows:
    CBC takes responsibility for the consequences of its decision to publish a person’s statements in the context it chooses. When we present a person’s statements in support of our reporting of facts, we ensure that the statements have been diligently checked. In the case of comments made by a person expressing an honest opinion, we ensure that the opinion is grounded in facts bearing on a matter of public interest.
    The interviewee also takes responsibility for his or her statement. As a general rule, we offer the interviewee no immunity or protection from the consequences of publication of the statements we gather.
    Sometimes the experts provide a recitation of facts, but not always. Often they are called on to analyze a situation or express an opinion related to their field. It is sensible that there is wide latitude in these cases for what constitutes reasonable comment. Realtors may disagree on which way the housing market is going. Marketers may clash over whether that new trend will fizzle. Doctors may have varying levels of enthusiasm for a prospective new drug.  
    The estimate of how much damage the average affected homeowner experienced during Toronto’s big summer storm of 2018 falls into this category of commentary and professional judgment. There is no single demonstrable number that has universal support, so the reporter went looking for someone to estimate the total.
    You disagreed with the Intact Centre’s methodology. Instead, you pointed to the CatIQ database, which is an excellent starting point. However, as you know, that database represents only the payouts insurance companies made to people who put in a claim. Others might think you should add in property damage not covered by the insurance policy, or people who opted not to file a claim. There are other expenses that could be considered as well. Should you include the value of time homeowners missed from work as a result? What about the cost of infrastructure repairs absorbed by government, or the cost of policing, firefighters and ambulance drivers? Should they be included or costed separately?
    Looked at through a different kind of prism, how much of the damage was caused by flooding, and how much was caused by wind, or by lightning? 
    Now, I recognize that you know a great deal about all these subjects. You have your own expertise, and you have told me about work you are doing that seeks to consider both direct and indirect costs to come up with a ratio of overall losses to insured losses. However, it is apparent that determining an estimate has at least some degree of subjectivity. 
    With all that in mind, it was acceptable journalistic practice for the CBC reporter to use the Intact Centre as its expert source and ask them to estimate the damage from a big storm. The Intact Centre is an applied research centre affiliated with the University of Waterloo. That may not bring it reputational immunity, but it does come with an inherent base level of credibility. The reporter was entitled to use Ms. Moudrak as an expert, so long as he attributed the estimate to her. I disagree with you that the JSP standard of “diligent checking” of her statement meant the reporter should have done extensive research to test that estimate. It is more reasonable to believe that diligent checking refers to facts that can be categorically confirmed or refuted, not to a matter of professional judgment such as this. 
    Nonetheless, you are correct that the number in the story WAS the wrong number, regardless of the quality of the estimate. The $43,000 figure did not represent the Intact Centre’s estimate for the 2018 Toronto storm, but instead was their estimate for the 2013 Toronto storm - something raised by you in your complaint, acknowledged by Mr. Hambleton in his response, and confirmed in my own communication with Ms. Moudrak.
    That this was wrong is, naturally, a violation of policy. That it has not been corrected means it continues to be so. It does not matter whether the original misunderstanding was caused by the source or by the journalist. It ought to be clarified for the record, and for the readers. 
    Further, I noted while reviewing the story that there is no note on the web page acknowledging the two other corrections prompted by your initial complaint. This is a second violation of policy.   
    I have a broader concern that there is a pattern of imprecision in CBC’s coverage relating to flood events. You provided me with a list of other recent CBC stories which make reference to the $43,000 damage estimate. Several confuse the matter by not indicating this is a specific estimate for the 2013 Toronto floods. One said, “The average basement flood in Ontario costs the homeowner $43,000.” Another said, “The average payout for a flooded basement is $43,000 and rising.”  These types of references take a single (and unusual) event in 2013 and treat it as if it is now a generic standard.
    Reporters and editors need to ensure they understand what's included (and what's not) in any estimates provided, and they need to ensure that they associate that estimate with the correct event - or events, as the case may be. Based on my review, that is not happening consistently enough. 
    All of this needs to be distinguished from your belief that the Intact Centre’s $43,000 estimate to be incorrect, even when attributed to the 2013 storm. I would encourage CBC News to take your perspective into account, but that is as far as I will go. It is not my intention to take sides on the quality of the Intact Centre’s estimate. If journalists continue to find the Intact Centre credible, they continue to be free to consult them for stories.
    Jack Nagler
    CBC Ombudsman

    Toronto Area Extreme Rainfall Trends - Comparing Engineering Climate Datasets with Future Weather & Climate Study Predicted Trends

    Environment and Climate Change Canada's Engineering Climate Datasets summarize observed annual maximum rainfall over various durations from 5 minutes to 24 hours.  Theses series are used to derive IDF tables and charts that describe the intensity, duration and frequency (i.e., return period) of extreme rainfall.  IDF tables are used to support engineering design of storm drainage and wastewater systems, and are used to define rainfall patterns used in hydrologic modelling.

    The City of Toronto commissioned Toronto's Future Weather & Climate Driver Study - the 2012 results indicate projected changes in extreme rainfall for a few durations and return periods.  Results of the Outcomes Report are here  The baseline period for the study is 2000-2009 and statistics are predicted out to 2040-2049.

    The Engineering Climate Datasets have been updated in early 2019, including for two Toronto-area climate stations with long records called "Toronto City" and "Toronto International Airport".  The following tables compares the predicted increase in extreme rainfall in the 2012 study with trends in the same statistics from 1990 to 2017 at these two Toronto-area stations.

    A key take away is that the Future Weather & Climate Driver Study does not agree with the direction and magnitude of changes in the actual statistics, which are based on real observations (not modelling predictions).  Some actual statistics have been decreasing since 1990, not increasing as predicted int eh study.  When a statistic is increasing, it is at a significantly lower rate that what is predicted in the study.

    The following chart compares the past 100 year daily data to the study predictions - the Toronto study seems to have a hockey stick shape, jumping significantly upward by the 2040's which does not match the past trends.

    The next chart shows changes in 10 year hourly rainfall. The Toronto study significantly understates the value today, suggesting it will double by the 2040's - the predicted future value has already been in place since the 1990's however.

    It is questionable whether the City of Toronto should consider any changes to design criteria for municipal infrastructure considering these future predictions - best to follow ASCE's approach and incorporate flexibility in future design and wait and see with the 'observational method'? - if observations show that there is no change in the statistics, there should be no significant driver in changing design criteria, especially based on models that do not match the magnitude or trend in actual extreme rainfall statistics.


    Bonus: here are a few more predicted 24 Hour 100 Year rainfall values, also going against the observed trends: