Green Infrastructure Capital and Operation and Maintenance Costs - City of Philadelphia Clean Waters Pilot Program Final Report

A previous post summarized budget costs for Philadelphia's extensive green infrastructure program, showing budget costs of $568,00 per hectare, comparable to recent Ontario LID project tenders with an average cost of $575,000 per hectare.

The Philadelphia Water Department's has also reported extensively on green infrastructure costs and performance in their report Green City, Clean Waters Pilot Program Final Report. Highlights are presented below.

Green Infrastructure Capital Costs (Construction)

"The median construction cost per unit of impervious drainage area was $353,719/ac" - that equates to $872,000 per impervious hectare (2015 dollars).

"Median construction cost per unit of storage volume (Greened Acre) is $248,365/ac-in" - that equates to $2416 per cubic metre.

Overall costs appear to be increasing over time as shown in the following chart - to convert cost per acre to per hectare, multiply by 2.47 :

Green Infrastructure Construction Cost by Feature Type

Capital costs vary according to the type of green infrastructure (called GSI in Philadelphia). The following chart shows the variability in cost per managed impervious area for various types, suggesting some economies of scale for larger managed impervious areas.

The following chart shows the range of cost, median and average cost per managed impervious acre. A high variability in costs is shown from project to project.

Construction Cost by Loading Ratio / Efficiency

The cost efficiency of a green infrastructure project can vary according to its loading ratio, i.e., the relative size of the contributing runoff area to the project area itself. The following chart shows how project costs decrease for larger loading ratios - costs at ratios of 15 or greater are 25% less than costs for ratios of 10 and under. Also it appears that costs level-off for ratios of 15 and greater (i.e., the average cost for a loading ratio of 15 or greater is the same as for a loading ratio of 10 to 15).

Green Infrastructure Operation and Maintenance Cost

Operation and maintenance costs have been reported as well and show a wide variability. The following chart shows cost per impervious drainage area by broad type of green infrastructure, whether a subsurface or surface feature. The data indicates that surface features - those that are vegetated - cost on average more than subsurface features to maintain.

The average cost per impervious acre of $8000 equates to about $20,000 per impervious hectare. The following chart shows the variability in operation and maintenance costs according to each specific green infrastructure type. The chart shows for example higher costs for surface bumpouts and rain gardens than subsurface trenches and basins. For example, on average a bumpout costs almost twice as much as a subsurface basin.

The operation and maintenance cost appears to be approximately $20,000/$872,000 = 2.3% of capital cost. Lifecycle replacement / reconstruction of green infrastructure features, based on their deterioration over time,  would generally add to this cost and could be considered to be 1-4% of capital cost depending on the service life of the feature (i.e., features that last 25 years add 4% depreciation, and those that last 100 years add 1%).

Using these unit costs, overall lifecycle costs for Ontario-wide implementation are explored below, assuming an initial 50-year build-out period and a range of green infrastructure measures with service life durations of 25 to 100 years.

Given 852,000 urban hectares in Ontario, and assuming these are 50% impervious, the cost of green infrastructure retrofits in this province would be $370 billion dollars in capital construction cost (using $872,000 per impervious hectare) - that compares to the current Ontario stormwater infrastructure deficit of $6.8 billion. The Ontario-wide annual operation and maintenance cost for 426,000 impervious hectares would be $8.5 billion assuming $20,000 per impervious hectare - that O&M cost is over 1% of Ontario's GDP. Based on these costs, green infrastructure policies that prescribe wide-spread implementation require careful review for affordability. To recap:

Capital cost = $366 billion (using slightly lower unit cost of $860,000 per Row 12 below)
Annual O&M cost = $8.5 billion
Annual depreciation = $7.2 billion
Annual lifecycle cost (O&M + depreciation (reserve/rebuild)) = $15.8 billion

The following table summarizes the unit costs and illustrates the Ontario-wide costs that should be a cause for concern.

Ontario Green Infrastructure LID Capital, Operation and Maintenance and Lifecycle Depreciation / Reconstruction Costs - Units Costs per Philadelphia Green City, Clean Waters Pilot Program Final Report  

The follow chart illustrates the time series of costs including initial capital construction, operation and maintenance ramp-up followed by sustained operation and maintenance, reserve contributions for lifecycle asset reconstruction / rebuild according to service life (assumed 1/3 25-year, 1/3 50-year and 1/3 100-year durations), and rebuild costs (starting in year 26). It is assumed that 50 and 100-year service life assets are rebuilt over 50 a 50 year period, similar to the initial construction period.

Ontario Green Infrastructure LID Capital, Operation and Maintenance and Lifecycle Depreciation / Reconstruction Costs - 50-year initial buildout and ongoing replacement of assets beginning in year 26, funded by annual reserve.

After the initial build, the average annual operation and maintenance and depreciation costs (that are reflected in the reserve and rebuild costs) is $15.8 billion.

Some academics, including those who promote green infrastructure for amenity or other stormwater management values, have proposed green infrastructure for the purpose of flood control as well. In order to achieve flood mitigation benefits, however, widespread implementation in the sewersheds or tributaries that have flood risks is required - in that case, the costs would appear to be prohibitive to achieve quantifiable flood reduction benefits. For illustrative purposes, a York Region 100 hectare catchment has recently undergone sewer capacity upgrades at a capital cost of approximately $20M and with nominal changes in net operation and maintenance cost (larger sewers replace older ones) and a 100 year service life - implementation was over 3 years. In comparison, the green infrastructure capital costs would be in the order of $872,000 * 50% impervious * 100 hectares = $44M with additional operation and maintenance costs and lower service life durations of 25-100 years, and long term implementation (over decades) with challenges on implementation on private properties, challenges with implementation in newer tributary catchment areas with low flood risk and high existing asset value (i.e., no co-benefits of watermain replacement, etc.). Basically, the conventional flood mitigation (grey infrastructure) approach is less expensive, has a shorter implementation time and more reliably addresses the flood risk issue (i.e., green infrastructure infiltration can aggravate wastewater inflow and infiltration stresses, can adversely affect foundations, and can be unreliable in high groundwater tables areas or during saturated conditions when green infrastructure storage in ineffective).

Some further case studies and detailed assessment are required to explore where and how some green infrastructure features can contribute to Ontario urban flood risk goals in a technically effective, timely and cost-effective manner. Similarly, analysis is needed to evaluate the strategic role of green infrastructure for achieving other stormwater management goals beyond flood risk mitigation.

***

How do Philadelphia GSI / green infrastructure costs compare to those of other jurisdictions? One can compare unit costs of $872,000 per hectare for Philadelphia's 1,100 projects with those in Onondaga County, New York. Costs for various types of green infrastructure measures are summarized in a recent article: http://stormwater.wef.org/2015/12/real-cost-green-infrastructure/http://stormwater.wef.org/2015/12/real-cost-green-infrastructure/.

The following chart illustrates lower unit costs with larger projects projects, similar to the Philadelphia reporting.

Green Infrastructure Unit Cost by LID (GSI) Type - Onondaga County, New York

These construction costs may be expressed as costs per area for projects. Considering projects managing 1 to 1.5 acres of impervious area the average cost per acre and hectare are summarized in the table below.

Green Infrastructure unit cost for projects managing up to 1.5 acres of impervious area  - Onondaga County, New York

 Excluding green roof projects, the average construction cost per impervious acres managed is over $368,000, or $783,000 per hectare. This cost is close to the Philadelphia cost of $872,000 per impervious hectare. Assuming 80% impervious surfaces in a catchment, the unit construction costs for project excluding green roofs in Onondaga County, New York is about $627,000 per hectare. This value is in the range of Ontario pilot projects with costs average costs of $575,000 per hectare.

The article citing Onondaga County green infrastructure costs notes that lower costs can be achieved by bundling implementation with other roadway works. In those cases costs were $320,000 per impervious hectare, or approximately $288,000 per total hectare, assuming 90% impervious coverage in those street projects.

Operation and maintenance costs for green infrastructure are summarized by CH2M as well. One observation that is similar to Philadelphia cost reporting is that vegetated systems are more costly to maintain than non-vegetated systems. The following chart summarizes costs per impervious area for various green infrastructure (LID, GSI) measures.

Green infrastructure operation and maintenance costs by type per impervious area managed.

Excluding green roof measures, a annual maintenance costs range from about $500 per impervious acre (low range for infiltration trench) to $3300 per impervious acre for tree infiltration trenches. A typical cost would be about $1500 per acre per year ($3700 per impervious hectare per year) which is 1500/368,000 = 0.4% of capital cost. This is significantly below the Philadelphia unit cost of $8000 per impervious hectare. It is also significantly below reported O&M/capital costs ratios reported in the American Society of Civil Engineers' report Cost of maintaining green infrastructure. In that report O&M costs for infiltration trenches and bioretention ranged from 5-20% and 5-7% respectively per one source (USEPA 1999 summarized by Weiss et al. 2007), and 8% for bioretention per another (Normalized UNHSC Installation and Maintenance Cost Data).

Are LIDs Financially Sustainable in Ontario? Philadelphia Green Infrastructure Costs - 1100 Low Impact Development Projects Define Implementation Funding for Long Term CSO & Water Quality Improvement - Comparison with 24 Ontario Projects

Philadelphia Green Stormwater Infrastructure Projects Map - Over 1100
Low Impact Development Projects for CSO Control

See September 2019 Update at Bottom of This Post

Philadelphia has an extensive green infrastructure retrofit program with cost information - recent Ontario low impact development project costs show comparable unit cost for implementation.

***

The City of Philadelphia implements green infrastructure (GI), aka low impact development (LID) best practices (BMPs), to control combined sewer overflows (CSOs).  Having implemented 1100 features in a retrofit setting, Philadelphia has a clear understanding of retrofit implementation costs. The following is a summary of their green infrastructure design construction costs provided by the city program staff:

City of Philadelphia Green Infrastructure / Low Impact Development Best Management Practices - Construction, Design and Planning Budgets Per Total and Impervious Area

Construction Cost
- $175,000 per acre ($432,000 per hectare)

Philadelphia Green Infrastructure Map by SWP / LID Type 

- $270,000 per impervious acre ($667,000 per hectare)

Design Cost
- Design fees typically 20-25% of construction costs

Total Cost (Design & Construction)

Philadelphia Green Infrastructure Map - Spatial Location
of Low Impact Development Measure

- Total costs of $230,000 per acre ($568,000 per hectare)
- Total costs of $350,000 per impervious acre ($865,000 per hectare)

Budgeting
-  $350,000 per impervious acre ($865,000 per hectare) is the overall target/budget cost that is achieved for the program and that does not include contingencies that could be carried for individual projects within the program.
- If estimated costs exceed $400,000 per acre ($988,000 per hectare) based on design estimates and project cannot be re-scoped, it is deemed too expensive and does not go ahead.

In Ontario, green infrastructure has been promoted for stormwater management in new developments since the Ministry of Environment's 1991 Interim Guidelines. Green infrastructure measures were promoted as part of a 'source control' approach and features that promoted infiltration were called Best Management Practices (BMPs). Since then, Ontario cities have developed design targets for achieving specific water resources management goals and have implemented LID BMP measures in appropriate locations. In the City of Markham and York Region, his history was summarized in a National Water and Wastewater Benchmarking Initiative Stormwater Task Force presentation:

Green Infrastructure / Low Impact Development LID Design Tool and Lifecycle Costing NWWBI Stormwater Task Force Robert Muir City of Markham from Robert Muir

The presentation above summarized LID implementation costs for nine (9) recent Ontario projects including bioswales, bioretention, infiltration galleries and permeable pavement. Theses cost are receiving close attention as LID implementation targets in some regions have been increased, e.g., through the Lake Simcoe Protection Act to meet environmental protection / phosphorus reduction goals, and as generic province-wide targets are now being evaluated by the Ministry of Environment and Climate Change.

Additional Ontario LID project implementation costs have been compiled with information shared by Ontario municipalities and also the Lake Simcoe Regional Conservation Authorit. This expands/updates the project costs in slide 17 of the above presentation. These costs include construction, design, administration and in-kind staffing efforts related to implementation of LID projects in the City of Markham (2 projects), City of Brampton (1 project) Town of Whitchurch-Stouffville (1 project), City of Ottawa (2 projects), Town of Ajax (1 project), City of Mississauga (3 projects), Town of Newmarket (2 projects), City of London (7 projects), Town of East Gwillimbury (1 project), Town of Uxbridge (1 project), Town of Aurora (1 project), Town of Innisfil (1 project).

The project costs and unit costs per total catchment are are shown below:

Ontario Green Infrastructure / Low Impact Development Best Management Practice Implementation Costs (No Adjustment for Inflation to 2018 Dollars) - Normalized Unit Costs Per Catchment Area Managed

This is a link to the above compiled Ontario LID costs (let me know if you have projects to add or can suggest edits / updates): Excel - Ontario Low Impact Development BMP / Green Infrastructure Implementation Cost Summary - 24 Projects

The average cost per hectare of $575,000 for these 24 projects is very close to the City of Philadelphia budget cost of $568,000. Cost per impervious hectare treated by the LID BMP would typically be higher (i.e., catchment is less that 100% impervious). Some notes regarding the project costs:

- complete costs are not available for some projects (e.g., Markham Green Road bioswale vegetation)
- one service area has been adjusted based on different sources (e.g., East Gwillimbury area reflect municipality's project brief and not original TRIECA 2017 presentation value).
- one projects has only tender cost estimate available, not actual construction cost (e.g., Newmarket Forest Glenn Rd)
- one project from LSRCA was not included in the list as it did not proceed to construction, but nonetheless incurred design and administration costs (e.g., City of Barrie, Annadale Recreation Centre, design/administration/geotechnical/in-kind staff cost of over $78,000) - this may reflect go/no go decisions on implementation that the others also consider
- most projects are retrofits, however some are new builds (Markham Green Road, Innisfil Fire Station)
- bioswales/enhanced swales require review given the wide range in unit costs per hectare of $51,000 (Uxbridge) to nearly $1.9M (Newmarket), with obvious sensitivity to the drainage area served

Previous cost estimates cited on this blog considered unit costs of approximately $400,000 per hectare and significant concern regarding the financial viability of any widespread implementation across Ontario's 852,000 urbanized hectares. Considering the expanded project cost review and adjusting for inflation, today's Ontario green infrastructure implementation costs can be estimated to be in the order of $600,000 per hectare. This magnitude of cost is comparable to Philadelphia's budgeting cost, considering over 1100 projects. These costs support the concern related to emerging Ontario policies that have not considered implementation cost impacts or financial viability.

The Ontario Society of Professional Engineers (OSPE) has recently highlighted concerns with the implementation of green infrastructure in Ontario in comments on Ontario's Long-Term Infrastructure Plan (my bold emphasis on the recommendations)

"....OSPE recommends that the Government of Ontario:

i. Critically apply the proposed ‘risk lens’ to infrastructure investments related to extreme
weather adaptation, recognizing variations in observed and predicted trends across the
province.

ii. Evaluate adaptation measures such as green infrastructure for stormwater management,
often cited as key mitigation measure, using the same ‘risk lens’ and consider the cost-
effectiveness of those infrastructure investments.

iii. Recognize that green infrastructure must be viewed through the same lens as
conventional infrastructure, adhering to established asset management principles and
full cost accounting—meaning it must be addressed up-front and directly, considering
system-wide costs."

OSPE has also commented on the limited role of green infrastructure for flood control and life cycle cost concerns in response to Ontario's draft Watershed Planning Guidance.

"Recommendation:

Green infrastructure LID implementation costs should be acknowledged to be potentially higher
than conventional grey infrastructure design, particularly for retrofits, and funding for additional
incremental retrofit costs should be considered in the comprehensive evaluation of alternative
management solutions beside green infrastructure and LIDs, including enhanced conventional
grey infrastructure designs with pollution prevention activities. Higher retrofit costs compared to
greenfield implementation should also be acknowledged.

Consideration for disproportionate costs should be acknowledged as a prohibitive constraint in
general and for linear development retrofits or widespread watershed implementation. A more
strategic approach to green infrastructure implementation, based on local needs and
considering local constraints (infiltration impacts and property flooding) is warranted."

"Recommendation:

The additional lifecycle cost associated with green infrastructure should be acknowledged to
support budgeting for long term operation, maintenance and depreciation.

The cost impacts of green infrastructure in existing communities should also be quantified
including costs in communities that are susceptible to infiltration stresses and sewer back-up
risks, additional treatment costs as infiltrated water is collected in foundation drains and
conveyed to treatment plants and cost of reduced service life of cast iron and ductile iron
watermains due to chloride infiltration in right-of-ways (i.e., accelerated corrosion). Such a
robust and holistic economic analysis can then support more strategic, financially sustainable
implementation policies for green infrastructure."

Let's work toward this sustainable implementation policies for all infrastructure - including green infrastructure - considering costs and strategic goals and specific performance outcomes. Low impact development implementation costs in the order of $600,000 per hectare, as shown through local and other jurisdictions, are simply not sustainable on a broad, system-wide basis.

RJM

***

September 2019 Update

Additional projects have been reviewed in Ontario and a couple have been added from Edmonton, Alberta.  The resulting average cost per hectare (area-weighted) is $581,000.  The following table presents a summary of cost per LID type (porous/permeable pavement, rain garden/bioletention, bioswale and infiltration/exfiltration).

The Ontario/Alberta costs now represent almost 8 hectares of catchment area, close to the EPA BMP database catchment area for projects with costs data (middle column).  Note that the Ontario/Alberta project costs may include several types of LID types in the treatment train.

Green Infrastructure Implementation Funding - Private Sector Costs Proposed as Offsets Paid by Benefiting Municipalities

How to fund green infrastructure and low impact
development stormwater management measures on
private property .... no easy answers. 

The report Economic Instruments to Facilitate Stormwater Management on Private Property is an interesting read, looking at how green infrastructure (GI) could be implemented and funded on private property to advance stormwater management goals. There is a link to the report.

The White Paper / study report explores the costs and benefits of green infrastructure, or low impact development (LID) measures, and looks at the barriers to implementation on private property - and there are many. These Barriers to the Implementation of LID Technologies include:

1. High up-front costs
2. Uncertain ongoing maintenance requriements
3. Low return on investment
4. Limited benefits accrue directly to property owners, yet they incur the high costs
5. High transaction costs

The report illustrates the types of costs and benefits under #4 in the following graphic:

Imbalance in public and private costs and benefits for green infrastructure / low impact development implementation.

The graphic illustrates that private costs are high, but the majority potential benefits are public.  Also, the private benefits are very low, like the potential reduction in stormwater management fees available to compensate for the GI or LID measures.

How high are the costs for implementing GI or LIDsfor improved stormwater management? Another interesting graphic shows annualized costs considering capital costs distributed over a 25 year service life (e.g., like annual depreciation of the asset) and annual operation and maintenance (O&M) cost.

LID capital and operation and maintenance costs greatly exceed the potential annual credit for stormwater fees. 

The report's impervious percentage of 20% seems too low
compared to typical urban development patterns in Ontario.
Typical residential percentages are double the report's
assumed value. Typical non-residential percentages can
even be higher (i.e., lots covered almost entirely by impermeable
roof top and parking lot surfaces.

The annual cost of LID measures averages about $5,000 per year considering a 'lot size' drainage area of 5000 square metres, or $10,000 per hectare. The cost estimates consider an area with 1000 square metres of impermeable area, meaning an impervious area percentage of 20% (i.e., very, very low for many urban areas ... meaning these average costs should be higher - see example impervious area coverage at right - while this is residential development, non-residential development has followed similar trends).

Given the disparity in costs and benefits, an obvious barrier to implementation of GI and LID on private property, what is proposed to incentivize implementation? Make someone else pay of course! Who pays? The Public Sector. They call this "OFFSETS" and explain it as follows:

"Offsets are payments offered to proponents of LID infrastructure in compensation
for costs incurred when significant benefits accrue to other parties. A principle of
equity or fairness underlies this type of compensation based on the argument that
costs should be borne proportionately by those who benefit from the green
investment.

Public sector contributions in the form of offsets are justified to achieve a balanced
approach to cost sharing that reflects how all costs and benefits are incurred. Doing
this requires identification and quantification of benefits.."

So ultimately, the idea is that the public pays regardless of whether GI or LID is implemented on public land or on private land. What could these costs be in Ontario and what are the impacts to Ontario taxpayers?

Ontario has over 850,000 hectares of urban land use that
does not have enhanced stormwater management control, and
could be eligible for green infrastructure (LID) retrofits.

Ontario's SOLRIS land use mapping indicates 852,000 hectares of urban land use as of the year 2000. Previously we've estimated the capital cost considering a unit cost of $390,000 per hectare based on Ontario tender costs - see image ar right. All this urban land would in all likelihood have no water quality treatment and be eligible for stormwater managment enhancements. How do we know? Table 1 in the Economic Instruments to Facilitate Stormwater Management on Private Property report indicates that despite the use of quality controls, "Use of enhanced controls is negligible." (see table below).

If we retrofit the untreated area with GI / LID, the annualized cost would be simply $10,000 per hectare x 852,000 hectares = $8.5 billion per year ... forever.

Assuming this cost is allocated to municipalities who benefit from the green infrastructure, and these municipalities distribute the cost to Ontario households, we can estimate the annual household cost. The 2016 census indicates that there are 5,169,170 private households in Ontario meaning a cost of $1650 per household per year. Given household after-tax income of $65,285, the green infrastructure cost would represent about 2.5% of this income.

The Ontario stormwater infrastructure deficit has been estimated at $6.8 billion. If green infrastructure / low impact development lifecycle costs are not funded annually by taxpayers, and debt is used to fund the infrastructure investment, like a green bond, this deficit would double in a single year, and increase by the more than the existing deficit each and every year.

Allocating GI / LID costs seems like a shell game.

Allocating GI / LID costs seems like a shell game, shifting private property costs to the public sector, shifting public sector costs to
the downstream municipalities that accrue potential benefits. In the end there is only one source of funding however.... all of us. Elaborate credit systems, offset schemes, Drainage Act assessments, and fancy 'green bonds' are ways of spreading out the high up-front cost of LIDs. But ultimately, we all pay.

It will be interesting to see the next stages of the study authors' work and how the White Paper could be applied. The report states for example "The White Paper also provides background for a pilot study to be undertaken in the Southdown area of Mississauga. This study will examine the potential of aggregating private commercial property under the Drainage Act to secure installation of communal LID technologies and realize cost-efficiencies." The exploration of the Drainage Act was part of another study under the banner "Aggregated Communal Approaches to Green Infrastructure Implementation". The Drainage Act allows costs to be distributed to landowners across catchments in which improvements are made - the challenge is that landowners against whom costs are assessed have to buy in to the cost-sharing plan and can appeal.

Green Infrastructure Implementation Constraints in Flood Prone Partially-Separated Wastewater Systems

So what happens when green infrastructure infiltrates runoff into the ground in a densely-developed city? Does it disappear and sustain an aquifer and watercourse baseflows? That's the theoretical benefit. Or does it end up in foundations drains (weeping tiles) making its way to the local wastewater treatment plant on low rain days and contributing to sewer back-ups on the high rain days? its the latter. It is surprising how quickly foundation drains respond to surface water inputs - Toronto Water presented at the National Research Council expert panel this week that it takes only 4 minutes for surface water to end up in foundation drains!

Municipal wastewater engineers have know this for a while - that systems with no apparent direct inflows of rainwater or runoff respond quickly to rainfall. My work on a Municipal Class Environmental Assessment in Kitchener, Ontario showed the greatest correlation of wastewater peak wet weather extraneous flows was to the 5-minutes rainfall intensity. Often we expect groundwater collection systems in cities respond slowly to rainfall volumes - they don't. The respond rapidly to short duration rainfall.

So what does this have to do with green infrastructure and the suite of sweet low impact development measures many are going gaga over? Well, its the impact of GI and LID runoff infiltration on wastewater systems. Quick and clear impact. At the NRC expert panel this week I summarized a list of documents that expressed concern for GI and LID wastewater system impacts including aggravated basement flooding due to this infiltration. This is the list:

1) Water Environment Association of Ontario (July 17, 2017 memo) 

Identifies concerns of interference with wastewater systems (flood impacts), water distribution systems (chlorides/corrosion), human health impacts to drinking water distribution (compliance with Procedure F-6-1), excessive costs:

https://drive.google.com/open?id=1T3vXEJ_nBi8e30KpcawVTfFPKx7A6y_v

2) City of Ottawa (February 23, 2017 letter)

Indicates "While the intent appears to be not to "make things worse or better" (specifically with respect to current condition runoff volumes), there should be recognition of situations in older neighbourhoods (with partially separated sewers, for example) where increased infiltration should be avoided given the cumulative impacts over time that could raise groundwater levels leading to increased risk of basement flooding, increased I & I to sanitary sewers, etc.”:

https://drive.google.com/open?id=12IQjlaKvbCakqx7Brw9DJ97Oi5a0OHx-

3) City of Barrie (July 10, 2017 letter) 

Identifies financial impacts, capital cost increase of 200%, lifecycle cost increase of 550%, concerns for “damage to private properties and excessive sewer infiltration”, LIDs “highly susceptible to failure due to sand accumulation” :

 https://drive.google.com/open?id=1HDd24FpFmLsFTAA7kEdC5mk8N8Oau8Ox

4) City of Guelph (June 28, 2017 memo)

"Guelph downtown stone rubble masonry heritage buildings are prone to flooding with raised groundwater elevation; any additional infiltration measures using LIDs may aggravate basement flooding due to leaky masonry walls and severe impacts on the buildings structural stability; in addition, impacts on aged infrastructures such as, watermain corrosion, potable water quality interference (F-6-1) and enhanced sanitary infiltration can be anticipated.”

https://drive.google.com/open?id=1OAnqraDz9NuBD1ZCsY4dzeDXeyZzf66-

5) City of Markham (July 14, 2017 memo)

Identifies sanitary infiltration impacts, adjacent property impacts, excessive capital cost based on completed tenders, high soft cost, high lifecycle costs, chlorides/watermain corrosion:

https://drive.google.com/open?id=1RGwiyeaqihdmjI2owDY0R-Cw9CcGbEKu

6) Ministry of the Environment / Workshop on Stormwater Quality Best Management Practices (1992)

Identifies impacts of on-site infiltration source controls called Best Management Practices (BMPs):
 " - basement leakage problems related to infiltration near housing
   - surcharging of sanitary sewers by short circuiting of infiltrated water”
Therefore the impacts of green infrastructure have been long-known in Ontario. Unfortunately, green infrastructure is often cited as a panacea for water resources challenges in Ontario, often when only narrow view of is taken that ignores existing municipal infrastructure systems and practical constraints associated with the infiltration of large quantities of chloride and contaminant-laden stormwater runoff.

7) US Transportation Research Board / Evaluation of Best Management Practices for Highway Runoff Control, Issue 565 (2006)

Identified inflow and infiltration (I/I) risks with infiltration green infrastructure (BMPs) in urban areas:
“In urban areas, unrestricted infiltration may exacerbate infiltration and inflow (I/I) problems in both separate and combined systems”

https://books.google.ca/books?id=jKR-CF7PG6AC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

7) City of Seattle / Street Edge Alternatives Project (city web site)

Identified bioretention groundwater impacts to adjacent properties through engineering analysis, indicating that green infrastructure introduces property flood risks:

"Our original hope for retaining flows and allowing infiltration into the native soils throughout the length of the block was not possible because some homes had an existing groundwater intrusion problem. To limit the potential for stormwater to adversely impact the residences of concern, our geotechnical engineers identified some swales that needed an impermeable liner.” :

http://www.seattle.gov/UTIL/EnvironmentConservation/Projects/GreenStormwaterInfrastructure/CompletedGSIProjects/StreetEdgeAlternatives/DrainageImprovements/index.htm

We could go on and on. The InfraGuide on inflow and infiltration, the CSA guideline on IDF curves - these all note the issue with infiltration stresses on wastewater systems.

Green energy in Ontario gave us smart metres that did not improve the flow of money. Green infrastructure can give us smart swales that will not improve the flow of groundwater .. OK, in partially-separated sewersheds.

Urban groundwater flow has been called the darkest of the dark arts, making hydrology look like algebra - call wastewater systems groundwater infiltration analysis something fancy like the RTK method and it sounds scientific, but there is really just a mysterious system of 'urban karst' of hidden pathways and problems lurking under the surface. A black box. Those of us in the industry who have worked closely on wastewater smoke and dye tests know that adjacent laterals 'speak to each other' and the subsurface flow is erratic and unpredictable.

As Jeff Goldblum said in Jurassic Park, 'Nature Finds a Way', and the natural flow of infiltrated water finds a way too ... right into foundation drainage and overtaxed wastewater systems. As Adrienne Barbeau said in The Fog "Be afraid, be very afraid" ... as there is huge fog surrounding green infrastructure and low impact development measures - we should re afraid of what these things will do to our wastewater systems.

Environmental Impacts of Green Infrastructure Construction - CO2 Emissions for Soil Removal and Aggregate Extraction & Transportation, Ontario Impacts

Etobicoke Infiltration System - Green Infrastructure for
Stormwater Infiltration and Low Impact Development

Like any infrastructure that requires material resources and energy to construct, green infrastructure is no different than grey infrastructure. This post looks at a typical low-impact-development (LID) feature for stormwater runoff control and estimates the CO2 impacts of its initial construction, excluding traffic impacts during construction, and excluding impacts for ongoing operation and maintenance, or rebuilding at end of lifecycle. Emissions are then scaled up across Ontario in light of green infrastructure policies being considered province-wide. The GHG emissions are huge for building green infrastructure !

For this example, consider a perforated pipe and gravel trenches for infiltration of stormwater runoff, like the Etobicoke Infiltration system pioneered in pre-amalgamation City of Toronto. This is a typical green infrastructure configuration - see Ryerson University's Planning and Design Manual at this link. We can assume a simple arrangement with the perforated pipe and gravel trench beyond the roadway, say in the boulevard.

Napkin - engineer's friend ... especially when
they run out of envelopes to scribble on the back of.

The construction of the perforated pipe infiltration system requires transport of various materials to and from the construction for initial construction. Lets assume we are considering 1 cubic metre of infiltration storage volume in the system. Some activities and their resulting kilometre-tonnes of transportation are estimated on this blog-napkin, if you will, aka an educated Fermi Estimate:

1) excavation, transport and disposal of native soil material - if the facility is in a retrofit setting the sodium adsorption ratio of the soil (due to road salt chloride accumulation over time) means reuse could be limited. Assume the disposal site may be a distance of 40 km from the construction site. For each cubic metre of infiltration storage, lets assume a 40% voids ratio in the gravel infiltration trench, meaning each cubic metre needs 1/0.4 - 1.2 cubic metres of soil disposed, and at a density of about 2 tonnes per cubic metre. So 40 x 1.2 x 2 = 96 km-tonnes of native soil haulage.


2) transport and placement of clear stone - assume aggregate comes from a quarry 40 km away from the site. For each cubic metre of infiltration storage, and our 40% voids ratio in the gravel, each cubic metre of storage needs 1/0.4 - 1.2 cubic metres of clear stone. At a density of 1.6 tonnes per cubic metre (3/4 inch clear stone), there is 40 x 1.2 x 1.6 = 76.8 km-tonnes of gravel haulage.

The OECD indicates pollution for truck transport in a report that indicates 140 grams of CO2 emitted per tonne-km. So adding 1 +2 above, a total of about 173.8 km-tonnes of green infrastructure construction to achieve 1 cubic metre of runoff storage results in 173.8 x 0.14 = 24.3 kg of CO2 emissions.

3) quarrying gravel - based on 4.32 kg CO2 emitted per tonne from this source, each cubic metre of infiltration storage with 40% voids requires 1/0.4 - 1.2 cubic metres of clear stone. At a density of 1.6 tonnes per cubic metre again, there is 4.32 x 1.2 x 1.6 = 8.29 kg CO2 per cubic metre of storage.

The MOECC is targeting 25 mm or more of green infrastructure storage and/or treatment which means per hectare of urban development with 50% rain/runoff there is 10,000 x 0.025 x 0.5 = 125 cubic metres of runoff and green infrastructure storage needed. So 125 x 24.3 = 3037.5 kg of CO2 emitted per hectare of urban area retrofitted with this low impact development feature. That is just haulage. To quarry the gravel adds 8.29 x 125 = 1036.8 kg per hectare. Total is 4074.3 kg per hectare of green infrastructure runoff treatment. Is that big?

Ontario has 825,000 hectares of untreated urban area.

Given the Ontario-wide 852,000 hectares of urban area that would need green infrastructure retrofits under the draft MOECC policy, the Ontario-wide CO2 emitted to initially build green infrastructure would be 852,000 x 4074.3 = 3,471,303,600 kilograms of CO2 emitted. Say 3.5 million tonnes of CO2 added.

So over 3 billion kilograms to build green infrastructure to manage runoff - you could argue there is some nominal climate mitigation offset-benefit if there is some type of vegetated pre-treatment filter before the perforated pipe / gravel infiltration. If so, that would be offset by the frequent inspection and minor maintenance visits by municipal crews, year after year.

Note in Canada the per capital emission was 20.1 tonnes CO2 equivalent in 2015 according to Environment and Climate Change Canada. So retrofitting green stormwater infrastructure in Ontario will emit CO2 equivalent to all the CO2 emitted by 172,000 Canadians over an entire year. That is just initial construction.

So that is just a neat Fermi Problem on green infrastructure to consider along the the other considerations on cost, cost-effectiveness, impacts to existing infrastructure, and need for scientifically-based local targets for green infrastructure. Currently, MOECC is considering blanket green infrastructure retrofit targets that do not consider any cost constraints or any no environmental impacts of construction like CO2 emissions. Earlier posts note that impacts to iron watermains and flood prone sanitary sewer systems was ignored. Let's hope a more holistic approach emerges that recognizes that we can't build millions of tonnes of infrastructure, green, grey or purple, and not have big impacts to emissions etc.

Green infrastructure for stormwater management, just like green energy for power supply has significant negative impacts. It should not be viewed as a panacea for urban stormwater and water resources management issues in Ontario. Check out this post on costs and other impacts.

Green Infrastructure: Solution to Urban Flooding in Ontario or Overpriced Panacea?

Ontario urban flood damages are real. Green Infrastructure (GI), or Low Impact Development (LID) stormwater management measures have been proposed as the solution to urban flooding as well as water quality impairment, stream erosion, and potable water supply security (aka Source Water Protection in Ontario).  And proponents have cited that it is CHEAPER to rebuild roads with GI or LID, so why not go "all in". It sounds too good to be true, right? The truth is the incremental costs are higher than conventional , so are operational costs. But the absolute costs for achieving targets proposed the Ontario Ministry of Environment and Climate Change (MOECC) are actually PROHIBITIVE, potentially consuming entire municipal capital budgets for decades.

Ontario has 852,000 untreated urban hectares ans a unit LID / GI

cost of almost $400,000 per hectare treated. That results in a very

high province-wide costs over 300 billion. Some recent tender costs

show even HIGHER unit costs for small scale installations.

Here's why GI or LID will not be part of Ontario flood risk reduction for our cities 'existing urban development areas. This is discussed under the topics of i) cost, and ii) existing infrastructure and property impacts that can increase flooding. We have included GI / LID retrofit implementation costs for all Ontario municipalities to show the big green pill we would have to swallow.

Background

These GI or LID stormwater Best Management Practices (BMPs) have been used for years to address stream erosion impacts due to change in water balance following development, and have been used to manage water quality impacts through vegetative source and conveyance controls, promoted in Ontario's 1994 Stormwater Management Practices Planning and Design Manual.

On November 15, 2016, the Environmental Commissioner of Ontario released a report, Urban Stormwater Fees: How to Pay for What We Need. The report cites the issues as follows “Stormwater runoff – from heavy rain or snowmelt – can cause flooding, stream or river-bank erosion, and water pollution" and then "calls on the province to require municipalities to recover the full costs of managing stormwater runoff; for example, by charging landowners a separate stormwater fee based on runoff volumes". It also says the "Ontario government should also require all municipalities to prepare asset management plans for both their grey (pipes, drains, etc.) and green (wetlands, green roofs, permeable pavement, rain gardens, etc.) stormwater infrastructure."

The Environmental Commissioner of Ontario is on the right track to promote asset management plans with full lifecycle accounting of infrastructure capital, operating and renewal costs. This is already a requirement for all municipalities by the end of 2016 as a condition of receiving federal Gas Tax funding. But no municipalities have done the deep dive into GI and LID impacts, because to date only demonstration, or pilot, projects have taken place. The demonstration projects often have heavy subsidies (donated profession design time, donated materials) that it is difficult to know the true implementation cost for a project, or the cost for municipal-wide implementation. Until now, so read on.

Proponents of GI and LID such as Credit Valley Conservation have reported that there are on average savings of 25% on road retrofits by applying LIDs:

"LID road retrofits save 25 per cent on average compared to traditional stormwater management practices."(1)

(1) http://www.creditvalleyca.ca/wp-content/uploads/2015/07/Advancing-Low-Impact-Development-as-a-Smart-Solution-for-Stormwater-Management-v1.pdf

And other proponents have reinforced this cost efficiency message, such as Green Communities Canada indicating "The Credit Valley Conservation has produced a number of case studies detailing road right-of-way low impact development projects, and has found that costs are consistently lower than expected and performance has exceeded expectations".

A thorough examination of cost claims reveals there are no such savings or efficiencies - GI or LID projects cost more, and the literature case studies for cost savings (typical rural estate residential developments in the southern US) are not applicable to the sustainable built form communities in most Ontario municipalities where urban flooding issues exist.

Reality Check - Prohibitive Cost of Green Infrastructure, Low Impact Development Retrofits in Ontario

GI / LID demonstration project, literature, and local project costs indicate excessive, prohibitively high costs for implementation when applied to target management areas

Incremental GI / LID implementation costs for additional elements beyond standard design features has been estimated based on completed projects and unit costs for various measures. The incremental, additional cost is $390,000 per hectare of service area (untreated catchment)(1).

The untreated urban area in Ontario is estimated by urban land use area in place in the late 1990’s – early 2000’s and equates to 852,045 hectares(2).

The incremental GI / LID implementation cost is therefore $390,000 x 852,045 = $332,000,000,000, i.e., over $330 billion. As an example, the City of Markham's portion of this cost is $4.18 billion which is considered prohibitive as it is equivalent to 34 times the city’s 2016 capital budget of $122.9 million(3).

Organizations such as Credit Valley Conservation has identified over 140,000 kilometers of municipal roadway in Ontario(4), equating to 281,621 hectares of right of way(5).

The incremental LID implementation cost for roadways alone, assuming no external property runoff is therefore $390,000 x 281,621 = $110 billion. This is considered prohibitive.

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(1) CVC, University of Toronto and TRCA demonstration projects per City of Markham analysis.

(2) SOLRIS Version 1.2 land cover GIS mapping, as compiled in the Ontario Land Cover Compilation Version 2.0

(3) City of Markham 2016 Budget, https://www.markham.ca/wps/wcm/connect/markhampublic/129bc6d6-2289-49a2-b199-8893c02af011/2016-Budget-Signed-v2.pdf?MOD=AJPERES&CACHEID=129bc6d6-2289-49a2-b199-8893c02af011

(4) http://www.creditvalleyca.ca/wp-content/uploads/2015/01/Grey-to-Green-ROW-Road-Right-Of-Way.pdf

(5) Assuming 20.1 metre, 66 foot right of way width

GI / LID demonstration project, literature, and local project costs indicate only severely limited, technically ineffective implementation of GIs / LIDs can be achieved considering even Ontario’s entire stormwater infrastructure deficit

The entire national infrastructure deficit for water supply, wastewater, stormwater and roads is $170 billion, of which stormwater comprises 23% or $39.1 billion(1). The Ontario stormwater infrastructure deficit has been stated as $6.8 billion (2).

Assuming all Ontario stormwater infrastructure deficit spending is allocated to LID implementation, the area that can be treated is about 17,400 hectares, or 2% of the untreated urban area of Ontario. This would result in an equivalent composite treatment volume of 0.5 mm, assuming a target treatment volume of 25 mm. It is suggested that even this considerable investment, although not prohibitive, would not result in a tangible benefit if only 2% of untreated area is addressed.

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(1) Canadian Construction Association, Canadian Public Works Association, Canadian Society for Civil Engineers and Federation of Canadian Municipalities. 2012. Municipal Roads and Water System. Volume 1

(2) Urban Stormwater Fees: How to Pay for What We Need, Environmental Commissioner of Ontario, November, 2016, https://media.assets.eco.on.ca/web/2016/11/Urban-Stormwater-Fees.pdf

GI / LID project implementation costs are more expensive than traditional servicing projects, contrary to promotional documents that indicate 25% savings

The CVC has reported that there are on average savings of 25% on road retrofits by applying LIDs:

"LID road retrofits save 25 per cent on average compared to traditional stormwater management practices."(1)

The reference for the average costs savings is from USEPA (2), but it does not in fact demonstrate such average savings for the two roadway project included in the reference.

The first road project is the 2^nd Avenue SEA Street in Seattle Washington. The USEPA gives the convention project cost of $868,803, and LID cost of $651,548, suggesting 25% savings. However the Seattle Public Utilities actual project costs of $850,000 (3) for the LID design suggesting very little savings (only 2.2%).  Seattle Public Utilities notes the high soft cost of associated with LID design as follows "This included an extensive design and communications budget due to the need to work closely with residents on the design."

The second project is Crown Street, Vancouver British Columbia, a street redevelopment project. The project added 79% of the capital cost in consultant design fees and aesthetic design features  (capital cost $396k, consultant and aesthetic design features cost $311k), which is line with Markham’s experience on Glencrest Park Raingarden implementation. The USEAP report notes that “Discounting the extra costs, the $396,000 construction cost is 9 percent higher than the estimated $364,000 conventional curb-and-gutter design cost.” The average cost of roadway LID retrofits is therefore 5-6% more than conventional design, or 38% more than conventional design if additional consultant fees and aesthetic design features are considered – this is 63% higher than the average reduced costs cited by CVC.

Other USEPA case studies are for rural, large lot subdivisions (e.g., Auburn Hills Subdivision, Southwestern Wisconsin, Gap Creek Subdivision, Sherwood Arkansas, Laurel Springs Subdivision, Jackson, Wisconsin, Mill Creek Subdivision, Kane County, Illinois, Prairie Crossing Subdivision, Grayslake, Illinois, Prairie Glen Subdivision, Germantown, Wisconsin) that are not relevant to Ontario urban areas and not relevant to urban roadway retrofits.

Detailed economic studies on source control implementation have acknowledged that implementation of source control (SC) GI / LIDs would be more costly in retrofit settings than in greenfield settings. For example, a study of the Rouge River watershed (4) identified:

“The average per-house costs of the intervention strategies for medium density residential development in urban greenfield areas is $2,785 while the average cost is $4,607 in urban retrofit areas. These values suggest that retrofitting old developments is more costly than integrating best practices into the new development. In addition, the Rouge River Study modeling results suggest that the surface water quality improvements from the urban retrofit areas are less than the surface water quality improvements from urban green field development under the SC (source control) scenario, relative to FBO (uncontrolled full build out).”

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(1) http://www.creditvalleyca.ca/wp-content/uploads/2015/07/Advancing-Low-Impact-Development-as-a-Smart-Solution-for-Stormwater-Management-v1.pdf

(2) https://www.h-gac.com/community/low-impact-development/documents/Reducing-Stormwater-Costs-through-LID.pdf

(3)http://www.seattle.gov/UTIL/EnvironmentConservation/Projects/GreenStormwaterInfrastructure/CompletedGSIProjects/StreetEdgeAlternatives/CommunityCostBenefits/index.htm

(4) http://www.greeninfrastructureontario.org/sites/greeninfrastructureontario.org/files/Final%20Rouge%20Report%20Nov%2030.pdf

Reality Check - Existing infrastructure and property impacts of GI / LID infiltration measures have been overlooked

Flooding and operational cost impacts of GI / LID to partially separated wastewater systems have been overlooked

It is commonplace that urban areas built between 1960 and 1980 are serviced by partially separated sewer systems that exhibit high extraneous flow rates during wet weather events. Analysis of historical flooding events in the City of Toronto (May 2000, August 2005, July 2013) demonstrates that the 1961-1980 era developments have the highest relative proportion of reported flooding (1). In the City of Markham, the proportion of properties flooded during the August 19, 2005 extreme rainfall was highest for partially separated properties serviced before 1980, with over 2.5% of properties flooded. In contrast, only 0.3% of fully separated properties were flooded. These data indicate that partially separated sewer systems are at significantly higher risk of flooding than new fully separated areas. Statistical analysis of wet weather flows by the City of Ottawa support the variability in risk for different systems, identifying average 100 year extraneous flow rates of 4.87 L/s/ha in partially separated systems and only 0.57 L/s/ha in newer separated systems (2).

Wastewater systems are sensitive to groundwater conditions that contribute to extraneous flow rates that cause property flooding / sewer back-ups. As indicated in the document Infiltration/Inflow Control/Reduction for Wastewater Collection Systems. A Best Practice by the National Guide to Sustainable Municipal Infrastructure, by the Federation of Canadian Municipalities and National Research Council:

"Uncontrolled infiltration/inflow in sanitary sewers can have very detrimental effects on social, economic and environmental aspects of urban areas. Excessive flows can severely limit the capacity of existing sewer systems to serve expanded populations. They also generate sewer backups, basement flooding and health risks, increase the operation and maintenance costs of the treatment and pumping facilities, and give rise to overflow of wastewater to streets or to watercourses."(3)

And further that inflow and infiltration (I/I) is affected by groundwater levels:

"Groundwater infiltration (GWI) — Flow deriving from groundwater flowing into the sewer cracks in the pipe, manholes, etc. This I/I component tends to be continuous and dependent on groundwater levels. "

City of Ottawa analysis of monitored extraneous flows also identified factors affecting these flows including age of pipe, and noted the importance of groundwater conditions:

“Other factors are more prevalent with respect to extraneous flows such as construction practices, type of material, groundwater levels, etc.” (4)

Given observed flood history data for wastewater systems and infrastructure management best practices, infiltration LID implementation in existing urban areas that is intended to replenish groundwater systems and raising groundwater levels (or have recharge intercepted in trenches or foundation drains in partially separated sewer systems), would put additional stress on wastewater. This would contributing to increased operating costs where infiltrated water enters the wastewater sewer system during moderate conditions, and increased sewer backups and overflows during extreme conditions. Where LID implementation has a tangible benefit on groundwater levels, it will have a tangible dis-benefit on I/I stresses.

The effect of infiltration LIDs on groundwater levels has been identified through numerous monitoring and analysis studies that have demonstrated:

i) local groundwater mounding potential in the vicinity of an infiltration LID, with increases of groundwater level of over 1 m for extreme events (5), and

ii) statistically significant regional scale increases in groundwater level following infiltration LID implementation (6), and

iii) recharge targets of 10 mm will result in extensive groundwater level increases, even up to surface(7).

The US Transportation Research Board in its Evaluation of Best Management Practices for Highway Runoff Control, Issue 565 has identified I/I risks with infiltration BMPs in urban areas:

“In urban areas, unrestricted infiltration may exacerbate infiltration and inflow (I/I) problems in both separate and combined systems; the likelihood of this scenario must be evaluated before constructing unlined infiltration systems.”(8)

Flooding impacts of GI / LID to adjacent properties have been overlooked

Comprehensive analysis of groundwater effects due to LID implementation has been completed for the North Markham Urban Area (Future Urban Area (FUA)), where coupled surface and groundwater modelling at a subwatershed scale allowed effects of groundwater recharge to be assessed in terms of groundwater levels. This comprehensive assessment leverages considerable long-term, investment in the development of the regional groundwater models, refinements to water quantity stress models in three tiers of Clean Water Act refinements, and further analysis refinement at a subwatershed level to refine and calibrate the modelling tools to assess local impacts.

In North Markham, the comprehensive modelling results indicate that groundwater levels will increase above existing levels in some areas even if low LID implementation targets for recharge (i.e., 4 mm event) are implemented. If more moderate targets (10 mm event) are implemented, “Most parts of the FUA show a rise in water table above existing conditions and the potential for ponded water in areas where it rises to ground surface”, according to the Phase 2 analysis report (page 79-80). Based on this detailed modelling, infiltration LIDs implemented in existing urban areas are predicted to impact groundwater levels, which in turn adversely affect I&I stresses as noted above, and also adversely affect adjacent properties.

The MOECC LID design guidance of 25- 33 mm, 625-825% greater than a target that can increase groundwater levels in some areas, and 250-330% greater than a target that can increase groundwater levels in most areas, would clearly increase groundwater levels significantly in most areas, resulting in significantly higher I&I impacts, and adjacent property impacts.

Other jurisdictions have opted to prevent infiltration from LIDs due to adjacent property impacts. This includes the Seattle 2^nd Avenue SEA Street swales where groundwater impacts to adjacent properties were identified through engineering analysis:

"Our original hope for retaining flows and allowing infiltration into the native soils throughout the length of the block was not possible because some homes had an existing groundwater intrusion problem. To limit the potential for stormwater to adversely impact the residences of concern, our geotechnical engineers identified some swales that needed an impermeable liner – for example, a six inch depth of natural clay material was used as the preferred material.”(9)

Similarly the Seattle Swale on Yale is lined to prevent water from infiltrating into the ground adjacent to the proposed developments (10).

****
More - check out this high level assessment of GHG /CO2 emission impacts of green infrastructure construction.

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(1) Analysis by R. Muir: http://www.cityfloodmap.com/2016/04/design-standard-adaptation-vs-climate.html

(2) City of Ottawa, Sanitary Sewer Extraneous Flow Analysis, E. Tousignant, P.Eng., October 1, 2008.

(3) Infiltration/Inflow Control/Reduction for Wastewater Collection Systems, A Best Practice by the National Guide to Sustainable Municipal Infrastructure, Federation of Canadian Municipalities and National Research Council, March 2003 https://www.fcm.ca/Documents/reports/Infraguide/Inflow_Infiltration_Control_Reduction_for_Wastewater_Collection_Systems_EN.pdf

(4) City of Ottawa, Sanitary Sewer Extraneous Flow Analysis, E. Tousignant, P.Eng., October 1, 2008.

(5) Villanova University, The Graduate School, Department of Civil and Environmental Engineering, The Observed Effects of Stormwater Infiltration on Groundwater, Matthew Damien Machusick, 2009

https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjso-_107XQAhWs6YMKHdtPA8gQFggjMAA&url=https%3A%2F%2Fwww1.villanova.edu%2Fcontent%2Fdam%2Fvillanova%2Fengineering%2Fvcase%2Fvusp%2FMachusick%252009Thesis%252004_28_09.pdf&usg=AFQjCNHoQDNxwHISnqTYOPM9le8jHbYYBA&sig2=8VmthXVnITZqjc5Qv8rRJQ

(6) Impact of Storm Water Recharge Practices on Boston Groundwater Elevations, Journal of Hydrologic Engineering 17(8):923-932 · August 2012

https://www.researchgate.net/publication/236325104_Impact_of_Storm_Water_Recharge_Practices_on_Boston_Groundwater_Elevations

(7) North Markham Subwatershed Study, Phase 2 Assessment.

(8) Section 2.2.3.2, https://books.google.ca/books?id=jKR-CF7PG6AC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

(9)http://www.seattle.gov/UTIL/EnvironmentConservation/Projects/GreenStormwaterInfrastructure/CompletedGSIProjects/StreetEdgeAlternatives/index.htm

(10) http://www.seattle.gov/util/cs/groups/public/@spu/@drainsew/documents/webcontent/01_013152.pdf

Conclusions

Ontario urban flood damages are real. Readers of this blog know we do our best to explain the causes. In general it is decades-old low design standards, constrained overland flow paths, and increasing imperviousness:

Low design standards post

Overland flow drives basement back-up risks (flood plain to flood drain) presentation

Increasing imperviousness / urbanization post

It is not aging infrastructure or extreme weather changes as the Environmental Commissioner of Ontario states - that narrative from the insurance industry has been shown to be incorrect and Engineering Climate Datasets for southern Ontario show mostly statistically significant decreasing trends in extreme rainfall.

Insurance industry data gaps / confusing predictions with data presentation

Decreasing southern Ontario rainfall extremes post

The cost to mitigate flooding are also real. If GI / LID is the solution, then the cost is prohibitive - and it would be at best a partial solution because the target storms are smaller than the events that cause flooding in Ontario cities, they may be ineffective for concurrent events (i.e., they are slow draining and may be full with a preceding 'small' storm when the 'big' flood-inducing storm arrives), and can in fact aggravate extraneous flow stresses causing flooding and increased pumping and treatment costs in existing urban areas where flooding is most acute. Here are implementation costs for Ontario municipalities, assuming $390,000 per hectare of untreated runoff and urban areas from the Ontario land use GIS layer:

Table 1 - LID Retrofit Cost per Ontario Municipality
LEGALNAME1 Ontario Municipality per Open Data GIS Dataset	Urban Area Built by 2000 Where LID Retrofit Can Apply per Ontario Land Classification v2 (Hectares)	Retrofit LID Cost at $390k Per Hectare (average unit cost)
City of Barrie	5836	$              2,275,397,213
City of Belleville	3418	$              1,332,359,598
City of Brampton	15925	$              6,208,581,693
City of Brantford	4955	$              1,931,925,803
City of Brockville	1287	$                  501,584,398
City of Burlington	8009	$              3,122,356,516
City of Cambridge	5921	$              2,308,519,800
City of Clarence-Rockland	2144	$                  835,827,798
City of Cornwall	2542	$                  991,133,787
City of Dryden	1861	$                  725,696,949
City of Elliot Lake	2730	$              1,064,168,391
City of Greater Sudbury	19652	$              7,661,598,386
City of Guelph	5678	$              2,213,801,129
City of Hamilton	24115	$              9,401,464,058
City of Kawartha Lakes	12128	$              4,728,354,653
City of Kenora	3367	$              1,312,596,571
City of Kingston	7458	$              2,907,682,499
City of Kitchener	8427	$              3,285,434,384
City of London	17389	$              6,779,305,984
City of Mississauga	24509	$              9,555,173,566
City of Niagara Falls	5748	$              2,240,932,529
City of North Bay	5179	$              2,019,170,839
City of Orillia	1816	$                  707,837,418
City of Oshawa	5985	$              2,333,212,619
City of Ottawa	41720	$            16,265,094,044
City of Owen Sound	1305	$                  508,882,595
City of Pembroke	958	$                  373,558,930
City of Peterborough	3793	$              1,478,849,856
City of Pickering	4208	$              1,640,664,574
City of Port Colborne	1914	$                  746,249,444
City of Prince Edward County	4163	$              1,623,173,462
City of Quinte West	4647	$              1,811,707,301
City of Sarnia	5551	$              2,164,011,985
City of Sault Ste. Marie	7892	$              3,076,804,186
City of St. Catharines	6170	$              2,405,396,352
City of St. Thomas	1925	$                  750,652,924
City of Stratford	1852	$                  722,205,744
City of Temiskaming Shores	1743	$                  679,548,131
City of Thorold	1701	$                  663,320,169
City of Thunder Bay	10507	$              4,096,288,663
City of Timmins	8338	$              3,250,583,737
City of Toronto	53697	$            20,934,317,510
City of Vaughan	12834	$              5,003,659,847
City of Waterloo	4475	$              1,744,655,113
City of Welland	3345	$              1,303,912,418
City of Windsor	10673	$              4,160,875,955
City of Woodstock	2224	$                  867,169,696
County of Brant	5686	$              2,216,581,813
Haldimand County	7119	$              2,775,288,639
Municipality of Arran-Elderslie	1414	$                  551,084,070
Municipality of Bayham	1014	$                  395,155,278
Municipality of Bluewater	1735	$                  676,521,836
Municipality of Brighton	1321	$                  514,996,590
Municipality of Brockton	1927	$                  751,144,149
Municipality of Brooke-Alvinston	850	$                  331,383,770
Municipality of Callander	128	$                    49,868,091
Municipality of Central Elgin	2077	$                  809,731,480
Municipality of Central Huron	1661	$                  647,390,450
Municipality of Centre Hastings	463	$                  180,647,927
Municipality of Charlton and Dack	376	$                  146,604,292
Municipality of Chatham-Kent	13837	$              5,394,323,927
Municipality of Clarington	5832	$              2,273,774,416
Municipality of Dutton/Dunwich	1008	$                  393,111,432
Municipality of French River	807	$                  314,690,899
Municipality of Gordon / Barrie Island	0	$                                     -
Municipality of Greenstone	5313	$              2,071,521,370
Municipality of Grey Highlands	2502	$                  975,432,137
Municipality of Hastings Highlands	733	$                  285,805,125
Municipality of Highlands East	90	$                    34,973,453
Municipality of Huron East	2131	$                  830,836,603
Municipality of Huron Shores	1093	$                  426,172,616
Municipality of Killarney	61	$                    23,736,685
Municipality of Kincardine	2539	$                  989,975,900
Municipality of Lambton Shores	2183	$                  851,038,224
Municipality of Leamington	2894	$              1,128,141,652
Municipality of Magnetawan	0	$                                     -
Municipality of Markstay-Warren	880	$                  342,927,554
Municipality of Marmora and Lake	580	$                  226,112,538
Municipality of McDougall	594	$                  231,498,467
Municipality of Meaford	1860	$                  725,003,971
Municipality of Middlesex Centre	3003	$              1,170,606,283
Municipality of Morris-Turnberry	963	$                  375,392,251
Municipality of Neebing	93	$                    36,298,005
Municipality of North Grenville	2151	$                  838,722,516
Municipality of North Middlesex	1751	$                  682,609,515
Municipality of North Perth	1881	$                  733,267,074
Municipality of Northern Bruce Peninsula	1822	$                  710,416,348
Municipality of Oliver Paipoonge	1245	$                  485,233,629
Municipality of Port Hope	1947	$                  758,959,886
Municipality of Powassan	520	$                  202,674,096
Municipality of Red Lake	872	$                  339,910,030
Municipality of Shuniah	1734	$                  675,872,717
Municipality of Sioux Lookout	2161	$                  842,301,440
Municipality of South Bruce	1325	$                  516,408,861
Municipality of South Huron	1863	$                  726,258,348
Municipality of Southwest Middlesex	1466	$                  571,575,162
Municipality of St.-Charles	16	$                      6,149,082
Municipality of Temagami	1303	$                  508,101,898
Municipality of Thames Centre	2424	$                  944,949,883
Municipality of the Nation	2410	$                  939,485,007
Municipality of Trent Hills	2174	$                  847,415,441
Municipality of Tweed	1185	$                  462,172,378
Municipality of Wawa	1540	$                  600,408,305
Municipality of West Elgin	1243	$                  484,716,088
Municipality of West Grey	2492	$                  971,344,445
Municipality of West Nipissing	1339	$                  522,031,631
Municipality of West Perth	1853	$                  722,240,831
Municipality of Whitestone	353	$                  137,630,668
Norfolk County	8760	$              3,415,266,857
Town of Ajax	3718	$              1,449,481,629
Town of Amherstburg	2071	$                  807,371,846
Town of Arnprior	581	$                  226,314,291
Town of Aurora	2608	$              1,016,659,934
Town of Aylmer	432	$                  168,376,078
Town of Bancroft	289	$                  112,551,886
Town of Blind River	1514	$                  590,232,933
Town of Bracebridge	2509	$                  978,204,048
Town of Bradford West Gwillimbury	2047	$                  797,863,137
Town of Bruce Mines	193	$                    75,131,081
Town of Caledon	6008	$              2,342,124,841
Town of Carleton Place	451	$                  175,867,256
Town of Cobalt	144	$                    56,315,417
Town of Cobourg	1293	$                  504,128,241
Town of Cochrane	1164	$                  453,760,153
Town of Collingwood	1616	$                  629,890,566
Town of Deep River	537	$                  209,481,069
Town of Deseronto	103	$                    40,148,857
Town of East Gwillimbury	2364	$                  921,792,141
Town of Englehart	199	$                    77,543,346
Town of Erin	1415	$                  551,627,926
Town of Espanola	926	$                  361,094,100
Town of Essex	2053	$                  800,459,612
Town of Fort Erie	3964	$              1,545,507,309
Town of Fort Frances	1080	$                  420,944,581
Town of Gananoque	326	$                  127,139,509
Town of Georgina	3197	$              1,246,579,464
Town of Goderich	580	$                  226,024,819
Town of Gore Bay	0	$                                     -
Town of Gravenhurst	1544	$                  602,074,960
Town of Greater Napanee	2169	$                  845,687,382
Town of Grimsby	1478	$                  576,075,133
Town of Halton Hills	3974	$              1,549,191,495
Town of Hanover	471	$                  183,437,382
Town of Hawkesbury	557	$                  217,068,738
Town of Hearst	985	$                  384,067,632
Town of Huntsville	2378	$                  927,265,789
Town of Ingersoll	843	$                  328,655,718
Town of Innisfil	3405	$              1,327,561,384
Town of Iroquois Falls	2241	$                  873,695,969
Town of Kapuskasing	1738	$                  677,425,339
Town of Kearney	0	$                                     -
Town of Kingsville	2644	$              1,030,852,823
Town of Kirkland Lake	1167	$                  454,918,040
Town of Lakeshore	4206	$              1,639,673,352
Town of Lasalle	2024	$                  789,108,809
Town of Latchford	395	$                  154,077,927
Town of Laurentian Hills	851	$                  331,629,383
Town of Lincoln	2321	$                  904,765,938
Town of Marathon	974	$                  379,664,152
Town of Markham	10732	$              4,184,077,556
Town of Mattawa	193	$                    75,367,922
Town of Midland	1307	$                  509,654,520
Town of Milton	5163	$              2,012,855,092
Town of Minto	1137	$                  443,277,766
Town of Mississippi Mills	1400	$                  545,724,456
Town of Mono	1175	$                  457,944,336
Town of Moosonee	277	$                  108,095,775
Town of New Tecumseth	2371	$                  924,379,844
Town of Newmarket	2963	$              1,155,229,192
Town of Niagara-on-the-Lake	2538	$                  989,510,991
Town of Northeastern Manitoulin and the Islands	253	$                    98,473,032
Town of Oakville	7890	$              3,076,128,752
Town of Orangeville	1174	$                  457,593,461
Town of Parry Sound	640	$                  249,515,892
Town of Pelham	1679	$                  654,750,050
Town of Penetanguishene	731	$                  284,989,341
Town of Perth	470	$                  183,323,347
Town of Petawawa	1503	$                  586,136,469
Town of Petrolia	419	$                  163,191,902
Town of Plympton-Wyoming	1450	$                  565,312,046
Town of Prescott	331	$                  129,157,039
Town of Rainy River	0	$                                     -
Town of Renfrew	520	$                  202,858,306
Town of Richmond Hill	6032	$              2,351,554,603
Town of Saugeen Shores	1504	$                  586,443,485
Town of Shelburne	363	$                  141,525,379
Town of Smiths Falls	528	$                  205,665,305
Town of Smooth Rock Falls	776	$                  302,682,206
Town of South Bruce Peninsula	1837	$                  716,258,415
Town of Spanish	596	$                  232,296,707
Town of St. Marys	608	$                  236,893,168
Town of Tecumseh	2187	$                  852,634,705
Town of the Blue Mountains	2173	$                  847,196,144
Town of Thessalon	220	$                    85,955,571
Town of Tillsonburg	1006	$                  392,085,123
Town of Wasaga Beach	2033	$                  792,687,733
Town of Whitby	5046	$              1,967,074,693
Town of Whitchurch-Stouffville	3244	$              1,264,781,098
Township of Addington Highlands	261	$                  101,920,378
Township of Adelaide-Metcalfe	967	$                  377,058,907
Township of Adjala-Tosorontio	1340	$                  522,549,171
Township of Admaston/Bromley	660	$                  257,322,857
Township of Alberton	82	$                    31,798,035
Township of Alfred and Plantagenet	1731	$                  674,863,952
Township of Algonquin Highlands	744	$                  290,208,605
Township of Alnwick/Haldimand	1707	$                  665,328,927
Township of Amaranth	835	$                  325,594,335
Township of Armour	407	$                  158,735,791
Township of Armstrong	151	$                    58,964,522
Township of Ashfield-Colborne-Wawanosh	1712	$                  667,285,055
Township of Asphodel-Norwood	759	$                  295,901,549
Township of Assiginack	0	$                                     -
Township of Athens	472	$                  183,858,432
Township of Atikokan	546	$                  212,910,871
Township of Augusta	1479	$                  576,461,095
Township of Baldwin	436	$                  170,165,540
Township of Beckwith	854	$                  332,769,726
Township of Billings	0	$                                     -
Township of Black River-Matheson	4110	$              1,602,287,635
Township of Blandford-Blenheim	1357	$                  529,110,531
Township of Bonfield	231	$                    90,034,491
Township of Bonnechere Valley	0	$                                     -
Township of Brethour	2	$                         807,012
Township of Brock	1704	$                  664,434,196
Township of Brudenell, Lyndoch and Raglan	0	$                                     -
Township of Burpee and Mills	0	$                                     -
Township of Calvin	291	$                  113,551,880
Township of Carling	95	$                    36,938,352
Township of Carlow/Mayo	0	$                                     -
Township of Casey	23	$                      8,842,047
Township of Cavan-Monaghan	1674	$                  652,469,363
Township of Central Frontenac	0	$                                     -
Township of Central Manitoulin	0	$                                     -
Township of Centre Wellington	2596	$              1,012,045,930
Township of Chamberlain	252	$                    98,385,313
Township of Champlain	1361	$                  530,575,434
Township of Chapleau	412	$                  160,437,534
Township of Chapple	0	$                                     -
Township of Chatsworth	1562	$                  608,934,564
Township of Chisholm	0	$                                     -
Township of Clearview	2436	$                  949,739,325
Township of Cockburn Island	0	$                                     -
Township of Coleman	762	$                  296,998,033
Township of Conmee	165	$                    64,455,714
Township of Cramahe	1071	$                  417,611,270
Township of Dawn-Euphemia	1299	$                  506,610,680
Township of Dawson	0	$                                     -
Township of Dorion	573	$                  223,568,695
Township of Douro-Dummer	1180	$                  460,023,269
Township of Drummond/North Elmsley	1091	$                  425,295,429
Township of Dubreuilville	465	$                  181,297,045
Township of Ear Falls	545	$                  212,586,312
Township of East Ferris	227	$                    88,578,361
Township of East Garafraxa	570	$                  222,305,545
Township of East Hawkesbury	765	$                  298,050,658
Township of East Luther Grand Valley	450	$                  175,516,382
Township of East Zorra-Tavistock	1080	$                  420,979,668
Township of Edwardsburgh/Cardinal	1394	$                  543,557,804
Township of Elizabethtown-Kitley	2054	$                  800,889,433
Township of Emo	0	$                                     -
Township of Enniskillen	888	$                  346,059,112
Township of Essa	1631	$                  635,837,895
Township of Evanturel	160	$                    62,227,658
Township of Faraday	15	$                      5,745,576
Township of Fauquier-Strickland	853	$                  332,743,411
Township of Front of Yonge	546	$                  212,945,958
Township of Frontenac Islands	556	$                  216,656,460
Township of Galway-Cavendish and Harvey	1481	$                  577,320,738
Township of Gauthier	0	$                                     -
Township of Georgian Bay	1426	$                  556,031,406
Township of Georgian Bluffs	2060	$                  803,187,664
Township of Gillies	0	$                                     -
Township of Greater Madawaska	0	$                                     -
Township of Guelph/Eramosa	1496	$                  583,118,946
Township of Hamilton	1958	$                  763,494,944
Township of Harley	214	$                    83,508,219
Township of Harris	78	$                    30,455,939
Township of Havelock-Belmont-Methuen	760	$                  296,103,302
Township of Head, Clara and Maria	617	$                  240,559,810
Township of Hilliard	46	$                    17,903,390
Township of Hilton	56	$                    21,815,645
Township of Hornepayne	732	$                  285,199,866
Township of Horton	498	$                  194,279,415
Township of Howick	861	$                  335,506,550
Township of Hudson	0	$                                     -
Township of Huron-Kinloss	1621	$                  632,048,446
Township of Ignace	778	$                  303,261,150
Township of James	0	$                                     -
Township of Jocelyn	0	$                                     -
Township of Johnson	0	$                                     -
Township of Joly	13	$                      5,035,054
Township of Kerns	0	$                                     -
Township of Killaloe, Hagarty and Richards	0	$                                     -
Township of King	3119	$              1,215,930,544
Township of La Vallee	0	$                                     -
Township of Laird	0	$                                     -
Township of Lake of Bays	978	$                  381,137,827
Township of Lake of the Woods	113	$                    43,859,359
Township of Lanark Highlands	420	$                  163,928,739
Township of Larder Lake	0	$                                     -
Township of Laurentian Valley	1053	$                  410,383,247
Township of Leeds and the Thousand Islands	2142	$                  835,257,627
Township of Limerick	148	$                    57,631,197
Township of Loyalist	1653	$                  644,539,591
Township of Lucan Biddulph	682	$                  265,726,310
Township of Macdonald, Meredith and Aberdeen Additional	54	$                    20,973,545
Township of Machar	96	$                    37,438,349
Township of Machin	1104	$                  430,330,484
Township of Madawaska Valley	0	$                                     -
Township of Madoc	382	$                  148,806,032
Township of Malahide	1462	$                  569,838,332
Township of Manitouwadge	1150	$                  448,532,117
Township of Mapleton	1607	$                  626,688,832
Township of Matachewan	0	$                                     -
Township of Mattawan	108	$                    42,280,422
Township of Mattice-Val Cote	380	$                  148,200,773
Township of McGarry	0	$                                     -
Township of McKellar	0	$                                     -
Township of McMurrich-Monteith	0	$                                     -
Township of McNab/Braeside	911	$                  355,015,193
Township of Melancthon	849	$                  331,173,246
Township of Minden Hills	1215	$                  473,874,055
Township of Montague	664	$                  259,050,916
Township of Moonbeam	459	$                  178,832,149
Township of Morley	0	$                                     -
Township of Mulmur	850	$                  331,445,174
Township of Muskoka Lakes	293	$                  114,209,770
Township of Nairn and Hyman	726	$                  283,059,529
Township of Nipigon	788	$                  307,296,211
Township of Nipissing	130	$                    50,640,016
Township of North Algona Wilberforce	68	$                    26,377,018
Township of North Dumfries	1298	$                  506,084,368
Township of North Dundas	1796	$                  700,030,452
Township of North Frontenac	804	$                  313,278,627
Township of North Glengarry	1948	$                  759,503,742
Township of North Huron	711	$                  277,103,428
Township of North Kawartha	265	$                  103,192,299
Township of North Stormont	1340	$                  522,487,768
Township of Norwich	1629	$                  635,171,232
Township of O'Connor	4	$                      1,614,024
Township of Opasatika	264	$                  102,867,740
Township of Oro-Medonte	3791	$              1,478,139,334
Township of Otonabee-South Monaghan	1442	$                  562,329,609
Township of Papineau-Cameron	665	$                  259,173,722
Township of Pelee	190	$                    74,210,035
Township of Perry	616	$                  240,094,901
Township of Perth East	2200	$                  857,739,934
Township of Perth South	1090	$                  424,769,117
Township of Pickle Lake	857	$                  333,936,385
Township of Plummer Additional	53	$                    20,657,758
Township of Prince	556	$                  216,577,513
Township of Puslinch	1231	$                  480,093,312
Township of Ramara	2010	$                  783,740,424
Township of Red Rock	537	$                  209,516,156
Township of Rideau Lakes	2222	$                  866,257,421
Township of Russell	1399	$                  545,496,388
Township of Ryerson	0	$                                     -
Township of Sables-Spanish Rivers	2525	$                  984,589,971
Township of Schreiber	192	$                    74,964,416
Township of Scugog	2526	$                  984,625,059
Township of Seguin	626	$                  243,963,297
Township of Severn	2678	$              1,044,150,980
Township of Sioux Narrows-Nestor Falls	0	$                                     -
Township of Smith-Ennismore-Lakefield	2575	$              1,003,949,492
Township of South Algonquin	835	$                  325,629,423
Township of South Dundas	2419	$                  942,897,265
Township of South Frontenac	2213	$                  862,617,095
Township of South Glengarry	2597	$              1,012,510,839
Township of South Stormont	2190	$                  853,731,189
Township of Southgate	1530	$                  596,513,594
Township of South-West Oxford	1464	$                  570,890,956
Township of Southwold	1255	$                  489,330,093
Township of Springwater	2971	$              1,158,316,891
Township of St. Clair	3090	$              1,204,570,971
Township of St. Joseph	0	$                                     -
Township of Stirling-Rawdon	803	$                  313,059,330
Township of Stone Mills	1276	$                  497,400,215
Township of Strathroy-Caradoc	1955	$                  762,065,129
Township of Strong	420	$                  163,849,792
Township of Tarbutt and Tarbutt Additional	0	$                                     -
Township of Tay	1054	$                  411,093,769
Township of Tay Valley	548	$                  213,805,602
Township of Tehkummah	0	$                                     -
Township of Terrace Bay	747	$                  291,348,948
Township of the Archipelago	420	$                  163,867,336
Township of the North Shore	1170	$                  456,268,908
Township of Tiny	2636	$              1,027,633,546
Township of Tudor and Cashel	113	$                    44,201,462
Township of Tyendinaga	916	$                  357,111,670
Township of Uxbridge	2328	$                  907,493,990
Township of Val Rita-Harty	1082	$                  421,795,452
Township of Wainfleet	1088	$                  424,312,980
Township of Warwick	897	$                  349,550,317
Township of Wellesley	1148	$                  447,426,862
Township of Wellington North	1766	$                  688,688,422
Township of West Lincoln	1809	$                  705,065,506
Township of White River	556	$                  216,788,038
Township of Whitewater Region	1730	$                  674,285,008
Township of Wilmot	1896	$                  739,319,666
Township of Wollaston	0	$                                     -
Township of Woolwich	2576	$              1,004,098,614
Township of Zorra	1813	$                  706,740,934
United Townships of Dysart, Dudley, Harcourt, Guilford, Harburn, Bruton, Havelock, Eyre and Clyde	563	$                  219,647,668
Village of Burk's Falls	154	$                    59,920,656
Village of Casselman	239	$                    93,201,137
Village of Hilton Beach	0	$                                     -
Village of Merrickville-Wolford	508	$                  198,156,583
Village of Newbury	59	$                    22,903,357
Village of Oil Springs	92	$                    35,798,009
Village of Point Edward	305	$                  119,007,984
Village of South River	170	$                    66,438,157
Village of Sundridge	180	$                    69,990,765
Village of Thornloe	5	$                      2,096,477
Village of Westport	2	$                         666,662
TOTAL	852,045	$ 332,178,923,064
	total hectares	total cost

The Environmental Commissioner of Ontario is right that we have to look at costs to address water resource management challenges in the province, including flooding. We have good models for this in the realm of Source Protection under the Clean Water Act has developed locally-driven, evidence based, semi-quantitative risk management policies for the significant risk. That process has also adopted cost-effective risk prevention policies to prevent future risks from occurring.

We can learn from the 15 year post-Walkerton Source Protection process that risks are not universal, nor are the appropriate solutions. For example, potable water quantity risks are not universal across the province: there are “more than 970 wellhead protection areas and 150 intake protection zones within the source protection areas in Ontario”[1]  But only 22 municipal systems have required Tier 3 water quantity stress assessments[2], indicating that water quantity stresses were confirmed at the earlier Conceptual, Tier 1 or Tier 2 evaluations. Of these systems with Tier 3 assessments, only 18 are groundwater systems that would require recharge management policies – this represents a very small fraction of potable water supplies. Applying this to urban flood risk areas would also show a high variability in risk and required solutions (Toronto basement flooding densities vary from > 4 properties per hectare to less than 0.5 per hectare depending on the topography / slopes).

Unfortunately, Green Infrastructure and Low Impact Development stormwater management measures have been proposed as a universal solution, regardless of local issues to address. regardless of more cost effective pollution prevention measures (ban fertilizers like we did with pesticides), regardless of clearly prohibitive implementation costs, and regardless of impacts to existing wastewater systems in existing urban areas.

When something is promised to solve all our problems and cost less, it is a "Trumpesque" proposition at best. Fulsome economic analysis shows that Green Infrastructure and Low Impact Development stormwater management measures are unaffordable for Ontario urban retrofits, and fulsome technical analyses shows that implementation would be counter productive for flood risk reduction where infiltration is already a chronic challenge in many Ontario cities, and should not be aggravated by additional recharge from well-meaning GI and LID measures.

---

[1] http://conservationontario.ca/what-we-do/source-water-protection

[2]  Personal communication with Program Services Section, Ministry of Natural Resources & Forestry

****

Recent reporting from Philadelphia in the US suggests private sector implementation costs of $625,000 to $750,000 per hectare for green infrastructure installations to address small storms resulting in CSO's:

https://www.environmentalleader.com/2018/03/philadelphia-stormwater-runoff/