Port Whitby
Sustainable
Community Plan
Technical Study:
Water and Wastewater
August 30, 2010
DRAFT
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Port Whitby Sustainable Community Plan
Technical Study: Water and Wastewater
Contents
Page
1.1
Existing Conditions
1
1.2
Opportunities
12
1.3
Challenges
12
1.4
Strategies
13
1.4.1
Water Conservation and Efficiency Measures
16
1.4.2
Rainwater Harvesting
24
1.4.3
Greywater Reclamation
31
1.4.4
Multifunctional Green Infrastructure
38
1.4.5
Stormwater Management Practices
44
1.5
Summary of Recommended Strategies
58
Port Whitby Sustainable Community Plan
Technical Study: Water and Wastewater
Water
This Technical Study summarizes the technical analysis and
research that was undertaken in support of the Port Whitby
Sustainable Community Plan (SCP). The information that is
summarized in this report was used as one of the inputs to the
development of the SCP’s recommendations.
1.1
Existing Conditions
Port Whitby, located on Lake Ontario and traversed by Pringle Creek, has several water
resources that are vital to the community, relied upon by local commerce and industry, and
integral to the natural environment.
Within the Port Whitby area, the main surface water feature (aside from Lake Ontario) is
Pringle Creek, which runs for 39km draining a watershed area of about 3,082ha that is
within the jurisdictions of the Town of Whitby and the City of Oshawa. The watershed, which
is governed by the enhanced water quality standards of the Ministry of Environment (MOE)
of Ontario, is home to several fish species of recreational fishing value (e.g., rainbow trout,
Chinook salmon)1, as well as vulnerable, threatened, or endangered (VTE) species like the
Redside Dace (Clinostomus elongates)2, 3. Overall, the watershed has 10% forest cover,
with the main wooded areas within Port Whitby shown in the figure below4. These
undeveloped areas serve an important watershed source protection function, as well as
providing various other ecosystem services and aesthetic benefits. Development has
generally been restricted in the immediate vicinity of the Creek, as these lands are subject
to seasonal flooding. Despite providing seasonal shelter to migratory birds, the Harbour is
not designated as a significant wildlife area.
1
407 East Draft Environmental Assessment Report, http://www.407eastea.com/downloads/chapterPDF/Chapter3_final.pdf 2
Note that the last recorded presence of four out of the five rare species identified by the Ontario Natural Heritage Information Center (NHIC) for Pringle Creek were last recorded in 1961, http://www.cloca.com/lwc/streams_index.php; http://www.407eastea.com/downloads/chapterPDF/Chapter3_final.pdf 3
http://www.mnr.gov.on.ca/286971.pdf 4
407 East Draft Environmental Assessment Report, http://www.407eastea.com/downloads/chapterPDF/Chapter3_final.pdf DRAFT
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Port Whitby Sustainable Community Plan
Technical Study: Water and Wastewater
Figure 1. Natural features within the study area and surroundings5.
An update to the Pringle Creek Master Drainage Plan Study conducted in 1999 calculated
the 100-year return period flood area in Port Whitby expected for 2017 based on planned
land use changes. The floodline encroaches upon properties in the Study Area (see figure
below).
Figure 2. Port Whitby floodlines for the 100-year storm (shown in blue) for the year 2017,
assuming no SWMPs. Wetlands and 5m topographical contours are also shown.
5
ViewDurham Internet Mapping Application, https://viewdurham.region.durham.on.ca/viewdurham/viewer.htm DRAFT
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Technical Study: Water and Wastewater
Climate change will bring additional stress to the water resources in and around Port
Whitby. According to Natural Resources Canada, Pringle Creek and the surrounding
watersheds are in the higher ranger of sensitivity and vulnerability to climate change (see
figure below). Recent scientific studies such as the “Canada in a Changing Climate 2007”
report indicate that flooding risk will likely increase due to expected increases in the
frequency and intensity of extreme precipitation events. Significant flood events have swept
through various parts of Ontario causing loss of life and damaged property (such as the
North Peterborough flood on July 15, 2005 which resulted in $95 million in insured losses),
and historical records show that these events have been increasing in frequency since the
1990si. In addition to flooding due to changing extreme weather patterns, Port Whitby is
vulnerable to floods resulting from water infrastructure deficiencies, as demonstrated by the
basement flooding that occurred in 2008 due to a backup of the sanitary sewer.
Figure 3. Sensitivity of River Regions to Climate Change6.
Currently there are no “green” infrastructure stormwater management practices (SWMPs) in
place in Port Whitby. Nonetheless, existing natural wetlands, such as the 22.8 ha Whitby
Harbour Wetland Complex (a provincially significant wetland with a high water table),
provide localized flood control and water quality benefits. These wetlands, along with the
Pringle Creek Valley, are classified as Environmentally Sensitive Areas (ESA) and as such
need to be protected from pollution. To address this need and to provide stormwater
management, runoff from roadways and buildings is collected in a dedicated stormwater
sewer system, which discharges to Lake Ontario.
However, concerns remain with surface water quality. Due to high bacteria levels and other
pollutants associated with the stormwater and wastewater discharges to the Lake, there
6
http://atlas.nrcan.gc.ca/site/english/maps/climatechange/potentialimpacts/sensitivityriverregions DRAFT
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Technical Study: Water and Wastewater
have been instances in which beaches in the region have been closed to swimming and
other recreational activities. The Durham Health Department has issued a general advisory
that recommends not swimming if it has rained in the previous two days.
The figure below shows higher than average infiltration potential areas within the Study
Area, which contribute to reducing runoff volumes and attenuating peak flows in the Pringle
Creek watershed. Surficial geology data available from the Ontario Geological Survey
indicates that there are soil groups on the site that are well drained (such as the alluvial
deposits around Pringle Creek), but the fine-textured deposits found throughout the rest of
the site may have low infiltration rates.
Figure 4. Infiltration Potential7.
7
CLOCA Technical Guidelines for Stormwater Management Submissions 2010 http://www.cloca.com/resources/Technical%20Guidelines%20For%20Stormwater%20Management%20Submission
s%20‐%20January%202010.pdf DRAFT
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Technical Study: Water and Wastewater
Potable Water
Water from Lake Ontario is withdrawn and treated to meet the needs of approximately 85%
of Durham’s residents, with the Whitby and Oshawa Water Supply Plants being the primary
sources of water for Port Whitby. The remaining 15% of Durham residents rely on water
withdrawn from private groundwater wells8.
The potable water supply for residential, commercial, and industrial users in Whitby is
provided by the Oshawa/Whitby Drinking Water Supply System, which includes two water
supply plants (WSPs) operated by the Regional Municipality of Durham. Both plants share
one distribution system that delivers a blend of the water to customers. In addition, there are
a small number of private users that rely on groundwater wells. The table below summarizes
some of the key information regarding these two plants:
Table 1. Water Supply Plant data9.
Whitby WSP
Water source
Lake Ontario
Plant
Single Class III direct filtration plant
Description
Approved
118,000 m3/day
Capacity
Major
1976
Construction
Dates
Distribution
Shared with Oshawa distribution
System
system
Adverse Water
Quality Incidents
2009: none
2008: 1 corrected same date
2007: 5 corrected same date
2006: 5 corrected same date
Oshawa WSP
Lake Ontario
Two co-located Class III conventional
plants
134,000 m3/day
Plant 1: 1904,1931,1992
Plant 2: 1953, 1960, 1965
Class III trunk system
1,260km of Class II watermains
5 reservoirs
7 booster stations
SCADA system
2,829 hydrants (in Whitby and Brooklin)
2009: 8 corrected same date
2008: 11 corrected same date, 1
corrected within one day
2007: 7 corrected same date, 5
corrected within four days
2006: 9 corrected same date, 1
corrected within one day
The average household in Whitby uses 449,000 litres of potable water per year, which is
less than the provincial (580,000L/yr) and national (695,000L/yr) household averages. On a
daily basis, the Town of Whitby overall uses a maximum of approx. 86,000 m3/day of
potable water, approaching the approved capacity of the existing Whitby WSP. Durham
Works Department is planning on expanding the Whitby WSP within the next 2-3 years10.
There is also a Water and Wastewater Master Plan study underway for the Region of
Durham.
8
Environment Canada, 2006 Municipal Water and Wastewater Survey. http://www.ec.gc.ca/eau‐water/default.asp?lang=En&n=851B096C‐1 9
Region of Durham, Oshawa/Whitby Water Annual Reports 2009, 2008, 2007, 2006, 2002. http://www.durham.ca/works.asp?nr=/departments/works/reports/reportsinside.htm&setFooter=/includes/works
Footer.inc 10
Personal communication, Ben Kloosterman, Region of Durham, Dept. of Works. 03/22/10. DRAFT
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Technical Study: Water and Wastewater
Figure 5. Location of existing WSPs in the Region of Durham11.
In 2006, the Region of Durham abstracted 7.65 trillion litres of freshwater from Lake Ontario
and 0.55 trillion litres from groundwater wells12. If water consumption increases
substantially, the Region would need to update or obtain a new Permit to Take Water from
the MOE.
As of 2000, the Lake Ontario-based water supply system in Durham served approximately
111,000 residential users; over 3,200 industrial, commercial, and institutional users; and
also nearly 300 municipal users13.
11
http://mddurham.com/departments/works/reports/2009/Map.pdf Environment Canada, 2006 Municipal Water and Wastewater Survey. http://www.ec.gc.ca/eau‐water/default.asp?lang=En&n=851B096C‐1 13
http://www.durham.ca/works.asp?nr=/departments/works/sewer/chartssewerandwater.htm&setFooter=/include
s/worksFooter.inc#sanitary 12
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Technical Study: Water and Wastewater
Figure 6. Existing Whitby Water Supply Plant, located south of Water Street (courtesy Bing
Maps).
Watermain breaks have been an issue in the past, with an average of 4.8 and 8.9 breaks for
every 100km of pipe in 2006 and 2007, respectively. Contributing to this fact is the age of
the watermains, which were reported in 2009 as having an average age of 25 years.
Typically, this kind of break is associated with cold weather and aging infrastructure.
Durham is addressing this issue by implementing a repair and rehabilitation program that
includes cement lining of cast iron watermains and a leak protection program. The average
age of the watermains in Durham is also lower than the average in other areas of Ontario,
but work remains to be done to further reduce the occurrence of breaks (see figure below)14.
Figure 7. Watermain breaks by municipality15.
14
Region of Durham, Annual Report 2008. http://www.region.durham.on.ca/departments/finance/annualreports/2008/2008AnnualReport.pdf 15
Region of Durham, Annual Report 2008. http://www.region.durham.on.ca/departments/finance/annualreports/2008/2008AnnualReport.pdf DRAFT
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Technical Study: Water and Wastewater
Wastewater
The average household in the Durham Region produces 496,000 litres of wastewater per
year. This is lower than averages of both the Province of Ontario and nationwide, which are
608,000 and 786,000 litres per year per household, respectively.
In Durham, wastewater is treated at one of 12 wastewater treatment plants in the region
(except for approx. 15% of users who are on a private septic system). All plants meet
secondary treatment standards and discharge to Lake Ontario. As of 2006, the maximum
daily outflow from the treatment facilities Durham Region was 343,661 cubic meters, nearly
two thirds of the total capacity of 550,912 cubic meters. There are 48 sewage pumping
stations and 1,400km of sanitary sewers16.
The wastewater generated in Port Whitby is treated along with the wastewater from the rest
of the town at one of three Water Pollution Control Plants (WPCPs), which are operated and
maintained by the Region of Durham. The table below summarizes some of the key
information regarding these three plants. Note that these are part of the larger York Durham
Sewer System (YDSS).
Table 2. Water Pollution Control Plant Information17.
Pringle Creek WPCP
Corbett Creek
Courtice Creek WPCP
WPCP
Effluent
Lake Ontario via Pringle
Lake Ontario via
Lake Ontario via Courtice
destination
Creek
Corbett Creek
Creek
Approved
15,000 m3/day
84,000 m3/day
68,200 m3/day
Capacity
Relevant
2008 Decommissioning of Planned modifications 2008 Commissioned
Construction
this plant has begun
to digesters 2010Dates
2014
Collection
392 km of gravity sewers (in Whitby, including Brooklin)
System
Figure 8. Existing Pringle Creek WPCP, located southeast of the intersection of Brock Street
South and Highway 401 (courtesy Bing Maps).
16
http://www.ec.gc.ca/Water‐apps/MWWS/en/publications.cfm Canadian Business Journal, http://www.canadianbusinessjournal.ca/business_in_action/municipal/durham.html; Durham Region, http://www.durham.ca/news.asp?nr=dnews/2008/may0208.htm 17
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Currently, biosolids produced at some of the WPCPs in Durham Region are recovered and
used as fertilizer for agricultural lands. The biosolids must meet the criteria set by the MOE
and the Ontario Ministry of Agriculture, Food, and Rural Affairs (OMAFRA). Contingency
disposal is available at the Duffin Creek WPCP by incineration18.
Figure 9. Wastewater process flow diagram typical of the systems used in Durham.19
Costs for water and wastewater services have been steadily rising in Durham Region, with a
recent combined increase of 7.4% in 201020, on top of past increases of 9.5% in 2008 and
9.5% in 2007. The cost increase is in accordance with the Region’s user pay philosophy21.
In 2010, the average residential user will pay approximately $180 every 3 months for water
and sewer services, though individual bills vary widely as the charges are based on usage.
The current rate structure is a decreasing block tariff (DBT) with three blocks, stepped at
45m3/quarter (which effectively subsidizes homeowners) and 4,500m3/quarter (which
effectively subsidizes industrial users).
Despite having separate sanitary and stormwater sewers throughout most of Durham
Region, there are recorded events when the sanitary sewage system has backed up and
caused basement flooding, as exemplified by the heavy rainfall experienced in August of
200822. There has been discussion in the Town of Whitby about implementing several
18
http://www.bvsde.paho.org/bvsaar/cdlodos/pdf/awardprocess875.pdf Region of Durham, http://mddurham.com/extcontent.asp?nr=/departments/works/sewer/sewageprocess.htm&setFooter=/includes/
worksFooter.inc 20
Region of Durham, How a Bill is Calculated. http://www.region.durham.on.ca/extcontent.asp?nr=departments/finance/water/howabill.htm&setFooter=includ
es/financewaterfooter.inc#rates 21
Region of Durham, User Pay Philosophy. http://www.durham.ca/finance.asp?nr=departments/finance/water/userpayphilosophy.htm&setFooter=includes/f
inancewaterfooter.inc 22
http://www.durham.ca/departments/works/sewer/basementflooding/NoticeBasementFlooding.pdf 19
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different measures to minimize the stormwater flows into the sanitary system to prevent
system backups and flooding, which include23:
ƒ Household level source controls (disconnecting downspouts and foundation
drains from the sewer system) and home isolation (installing backwater valves
and sump pumps)
ƒ Construction of retention facilities
ƒ Specific improvements in key affected neighbourhoods, as well as system-wide
modifications to increase capacity and reduce infiltration and inflow (I and I)
Stormwater
Durham Region has a separate storm sewer collection system, which discharges to natural
waterways and storm retention ponds. The budget for sanitary sewerage operation for
Durham Region includes funding for the maintenance of regional storm sewers.
There are no “green” stormwater management practices (SWMPs) that have been
implemented within the Port Whitby area. One retention pond has recently been constructed
immediately east of the Study Area, on the eastern shore of Pringle Creek, north of Watson
Street East. Stormwater runoff currently discharges directly into Whitby Harbour or surface
water bodies that flow into Whitby Harbour via a dedicated stormwater sewer or open
drainage channels.24
23
24
http://www.durham.ca/works.asp?nr=/departments/works/sewer/basementflooding/basementflooding.htm Development Context Report, Port Whitby Sustainable Community Plan DRAFT
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Technical Study: Water and Wastewater
Figure 10. Existing regulated land under CLOCA’s jurisdiction25.
25
CLOCA, Technical Guidelines for Stormwater Management Submissions, 2010. DRAFT
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1.2
Opportunities
By integrating localized and district-wide sustainable stormwater management practices
(SWMPs) throughout Port Whitby, there is an opportunity to minimize flooding events,
reduce contaminant and thermal pollution loadings, and contribute to the “green” aesthetic
of the site, while improving the water quality in Pringle Creek, Whitby Harbour, and Lake
Ontario. Since “green” SWMP strategies are currently not present in the Study Area, the
connection between their implementation and the benefits they provide will be easily seen.
There are also opportunities to take advantage of synergies with other project features, such
as installing bioswales along the edges of new streets or implementing green roofs atop
new buildings. Public access to surface water features can be enhanced with greater
treatment of stormwater and wastewater, for instance by reducing beach closures
associated with rainfall events.
The water and wastewater service in Port Whitby is already of an above-average quality and
reliability with respect to provincial norms, including resource-efficient practices like the
recovery of biosolids at some of the existing Water Pollution Control Plants. However, there
is still room to improve upon this by setting a new standard of reduced water consumption
and treatment costs through conservation, efficiency, reclamation, and rainwater harvesting
measures, among other strategies. Decreases in water demand are critical to ensure that
the Town is able to meet the challenges ahead from a growing population and greater
climate extremes, such as predicted increases in drought conditions, especially in the
summertime when demand is highest. Analysis of the sources of demand and their
seasonal variations demonstrate that certain types of demand, like irrigation, increase
greatly in the summer months, adding to the stresses in that season due to increased
domestic water use. A comprehensive strategy looking both at population and climate
projections will allow for a robust and holistic water management system for Port Whitby.
The open space available on the site, combined with higher density, more concentrated
development, makes it feasible to implement natural stormwater and wastewater treatment
systems that can provide aesthetic and habitat benefits in addition to low cost, highly treated
effluent. These can increase the resilience of Port Whitby to a changing climate and restore
the water environment to more pristine conditions.
1.3
Challenges
New development on the site should minimize demand for potable water to ensure that
excessive stress is not placed on surface water or groundwater sources. There are strict
permits governing the amount of water that can be withdrawn from Lake Ontario, and
increases would require new or revised permits. Water quality is also a concern, with cases
like elevated chloride levels in the groundwater in the vicinity of the site, and variability in
quality of Lake Ontario’s water due to stormwater and wastewater discharges. Rainwater
quality will also need to be determined in order to assess the possible impacts of acid rain
and on the design of the treatment process for the proposed rainwater harvesting system.
The cold climate and relatively consistent year-round precipitation require special
consideration in selecting and designing any outdoor water strategies. For instance, MOE
has documented cases where roofs with water collection infrastructure have overfilled and
caused flooding damages due to inadequate sizing and overflow systems for extreme
precipitation events.
Any alternative paving systems (e.g. porous concrete, permeable pavers) would need to be
compatible with existing operations and maintenance practices such as salting, sanding and
snow removal. Redundancies would be required for systems that rely on infiltration in order
to allow for proper functioning during freezing conditions.
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Surficial geology data available from the Ontario Geological Survey indicates that there are
soil groups in the Port Whitby area that are well drained (such as the alluvial deposits
around Pringle Creek), but the fine-textured deposits found throughout the area will require
further evaluation to ensure their compatibility with any sustainability strategies that are
being considered. The low-lying nature of much of the Port Whitby area, and high water
tables could also present challenges to implementing some of the recommended
stormwater measures, and would require further study.
The context of growth and development elsewhere in the Town must also be taken into
consideration when examining the opportunities in Port Whitby, because both natural water
processes and municipal water services occur on a larger scale than one community. Many
of the strategies recommended in this plan can have a much more significant impact on
water resource management and protection if implemented on a watershed level.
Figure 11. Average precipitation in Whitby by month, showing rainfall and snowfall.
1.4
Strategies
The water cycle in Port Whitby can be advanced into a sustainable balance by implementing
a total water design that incorporates sound water management principles and appropriate
technologies, considering together all aspects of the natural and anthropogenic hydrologic
cycles. The main principles guiding this design include minimizing water consumption,
maximizing the efficiency of the water supply system and eliminating losses, having a
closed loop of resources within the site, and reducing the energy and resource costs of
providing centralised water and wastewater treatment. A variety of stormwater management
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practices can be integrated throughout the site that would significantly improve water quality
and reduce flooding concerns, while simplifying most construction and maintenance
operations and creating multifunctional space.
Figure 12. Total water design strategies and interrelationships.
The following water strategies and measurable outcomes are proposed. These are
developed in detail in subsequent sections of the report, outlining for each one the main
benefits, technical feasibility, financial feasibility, and supporting case studies where
relevant:
• conservation and efficiency measures
• rainwater harvesting
• greywater harvesting
• multifunctional green infrastructure
• stormwater management practices
As a result of this holistic approach to water management, an overall 82% reduction in
potable water demand (resulting in a 70% reduction in wastewater flows) is targeted through
the various proposed strategies.
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Figure 13. Water management strategies for Port Whitby, presented hierarchically.
Guidelines provided by the Canada Green Building Council’s (CGBC) LEED Green Building
Rating System will be used as a baseline for the analysis. Outlined below are the main
requirements for credits under the guidelines for Water Efficiency (WE)26.
26
•
WE Credit 1.1 – Water Efficient Landscaping: Reduce by 50%
ƒ Limit or eliminate the use of potable water, or other natural surface or subsurface
water resources available on or near the project site, for landscape irrigation
ƒ Reduce potable water consumption for irrigation by 50% from a calculated midsummer baseline case
ƒ Reductions shall be attributed to any combination of the following items:
o Plant species factor
o Irrigation efficiency
o Use of captured rainwater
o Use of recycled wastewater
o Use of water treated and conveyed by a public agency specifically for
non-potable uses
•
WE Credit 1.2 – Water Efficient Landscaping: No Potable Water Use or No Irrigation
ƒ Eliminate the use of potable water, or other natural surface or subsurface water
resources available on or near the project site, for landscape irrigation
ƒ Option 1 – Use only captured rainwater, recycled wastewater, recycled graywater,
or water treated and conveyed by a public agency specifically for non-potable
uses for irrigation
ƒ Option 2 – Install landscaping that does not require permanent irrigation systems.
Temporary irrigation systems used for plant establishment are allowed only if
removed within one to two years of installation.
LEED Canada NC 1.0, 2004. DRAFT
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•
WE Credit 2 – Innovative Wastewater Technologies
ƒ Reduce generation of wastewater and potable water demand, while increasing
the local aquifer recharge
ƒ Option 1 – Reduce potable water use for building sewage conveyance by 50%
through the use of water-conserving fixtures (water closets, urinals) or nonpotable water (captured rain-water, recycled graywater, and on-site or municipally
treated wastewater).
ƒ Option 2 – Treat 100% of wastewater on-site to tertiary standards. Treated water
must be infiltrated or used on-site.
•
WE Credit 3.1 – Water Use Reduction: 20% Reduction
ƒ Maximize water efficiency within buildings to reduce the burden on municipal
wastewater
ƒ Employ strategies that in aggregate use 20% less water than the water use
baseline calculated for the building (not including irrigation) after meeting the
Energy Policy Act of 1992 fixture performance requirements. Calculations are
based on estimated occupant usage and shall include only the following fixtures
(as applicable to the building): water closets, urinals, lavatory faucets, showers
and kitchen sinks.
•
WE Credit 3.2 – Water Use Reduction: 30% Reduction
ƒ Maximize water efficiency within buildings to reduce the burden on municipal
wastewater
ƒ Employ strategies that in aggregate use 30% less water than the water use
baseline calculated for the building (not including irrigation) after meeting the
Energy Policy Act of 1992 fixture performance requirements. Calculations are
based on estimated occupant usage and shall include only the following fixtures
(as applicable to the building): water closets, urinals, lavatory faucets, showers
and kitchen sinks.
To achieve a truly sustainable community, the proposed development must consider sitespecific factors and aim to meet and exceed the CGBC or equivalent guidelines.
1.4.1
Water Conservation and Efficiency Measures
When implementing a sustainable water strategy with new development, the first key step is
to apply conservation techniques and utilize an efficient design. Conservation and efficiency
are the most cost and performance effective strategies in reducing water demand, as
exemplified by the many municipalities throughout Canada that have implemented initiatives
to conserve water.
The water demand for Port Whitby can be reduced through operational, economic, and
socio-political conservation techniques, which include the following:
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•
Operations
o Leak detection systems throughout the potable water supply system using
remote data transmission to speed the discovery of leaks and associated
repairs.
o Water use restrictions for uses that do not require potable water.
o Plant and distribution network improvements.
•
Economic
o Consumption-based water tariffs and other pricing strategies, based on
local willingness-to-pay. This would expand upon the existing “User Pay”
philosophy set in place by the Region of Durham.
o Incentives through rebates and tax credits.
o Sanctions and/or fines for water misuse and other violations.
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•
Socio-political
o Universal building-level metering with real-time display of water usage,
using a system like Lucid Design Group’s Building Dashboard®.
o Consumer education campaigns targeting the full age-spectrum.
o Information transfer and training
o Regulatory changes (e.g., legislation, codes, standards, bylaws)
Figure 14. Real-time consumption monitoring and trend-tracking with Building Dashboard®27.
In addition, a water-efficient design can further reduce water demand by implementing the
following strategies:
• Installation of efficient water fixtures, appliances and HVAC systems within
residential, retail, and office buildings
• Recovery of HVAC condensate and other process water for reuse in large buildings
• Integration of best practices for water use on a building level, such as running full
dishwasher loads, minimizing water used for cleaning, etc.
• Selection of appropriate landscape plantings and use of xeriscaping principles,
including a site-grading plan to allow for optimal usage of rainfall
• High efficiency irrigation systems with appropriate leak detection and climateresponsiveness, coupled with best practices for irrigation
• Fire protection using high efficiency sprinklering and reclaimed water for use in
hydrants
Figure 15. Fire hydrant supplied with reclaimed water and high efficiency sprinklers.
Benefits
Reducing the water footprint of Port Whitby will bring about a number of economic,
environmental, and social benefits, including the following:
• Reduced costs and energy demands throughout the municipal water supply
system, starting with treatment costs at the Water Supply Plants, pumping costs
throughout the system, and minimized wear on the system as a whole
• Target of zero nonrevenue water (losses) for the utility
27
http://www.luciddesigngroup.com/kiosk/features.php DRAFT
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•
•
•
•
Potable demand that must be supplied by the municipal system will be reduced by
51%, freeing up that water capacity for other growth within the region or to provide
system redundancy
Less water extracted from Lake Ontario, minimizing the environmental impacts to
this water body, as well as less water extracted from groundwater, minimizing
depletion of this finite resource
Greater resilience to climate change and mitigation of the climate change impacts
due to water treatment and conveyance
Less cost to the user, as they benefit from the overall system efficiencies and their
own reduced use
Technical Feasibility
Based on the land use assumptions for the Sustainable Community Plan’s Recommended
Land Use Concept, along with typical water demand data, a baseline potable water demand
for the buildings in Port Whitby has been determined. Typical design values relate number
of people or gross floor area to average daily demand per unit. The following table outlines
these calculations, resulting in an average daily water demand of approximately 5,000
m3/day, or 1,800,000 m3/year.
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Table 3. Baseline building water demands.
Average Daily
Water Demand
(L/day)
Building Use
Commercial
Retail
513,750
Commercial Office
2,410,644
Restaurant (Open more than 12 hours)
90,000
Laundromat (self-service)
100,000
SUB-TOTAL
Institutional
3,114,394
Schools (including staff)
With cafeterias, showers and laboratories
47,500
Church
7,500
GO Transit Station
50,000
SUB-TOTAL
Recreational
105,000
Parks
Picnic parks with restrooms
3,500
Assembly Halls
6,250
Iroquois Park Sports Centre
25,000
Harbor Green
2,500
Heydenshore Pavillion
13,750
Public Lavatory
1,800
Sport/Gym
125,000
Marina and Clubhouse
100,000
Whitby Yacht Club
40,000
SUB-TOTAL
314,300
Residential
Multiple Family Dwelling (apt.)
2,473,200
SUB-TOTAL
2,473,200
TOTAL
6,006,894
Project Country Annual Domestic Use (m3pcy)
140
United States Annual Domestic Use (m3pcy)
203
Water Demand Factor
Adjusted Water Demand (L/day)
Annual Water Demand (m3/yr)
69%
4,910,230
1,792,234
NOTES
1. The estimates above have been compiled from the following sources:
- U.S. Department of Energy, Energy Efficiency and Renewable Energy Federal Water Use
Indices from American Water Works Association 1996.
- NJDEP Bureau of Safe Drinking Water Safe Drinking Water Regulations (N.J.A.C. 7:1012.6)
- Tchobanoglous, G., Schroeder, E., Water Quality, 1987.
2. A water demand factor is applied for projects where the water usage demands are different
from the United States average.
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We estimate that conservation strategies can reduce the baseline building demand for Port
Whitby by 22%. This is based on data from other similar communities where the operational,
economic, and sociopolitical strategies outlined above have been implemented. This
reduction comprises:
• 5.0% reduction through advanced leak detection technology, along with plant and
distribution network improvements
• 6.8% reduction in commercial and institutional building demands through
compulsory automated metering,
• 5.0% reduction through consumer education campaigns, mandated building-level
metering and real-time display of water usage, updates to regulations
• 5.1% reduction through economic incentives (sanctions and fines for water
misuse, tax credits and rebates for conservation) and a conservation tariff
structure that account for reuse and encourages water savings (e.g., an
increasing block tariff)
Adding in water efficient building design, the building baseline can be reduced by a further
30%. New and retrofitted buildings can include low-flow fixtures (e.g., dual-flush toilets can
save 73% per use, urinals can save 67% per use, faucets can save 17% per minute,
showerheads can save 50% per minute), high efficiency appliances (e.g., clothes washers
can save 40% per use, dishwashers can save 33% per use), and high-efficiency heating,
cooling, and fire-protection systems. Large buildings can incorporate systems for recovery
of HVAC condensate and other process water for reuse.
Part of a sustainable community design is planting vegetation, including establishing and
maintaining green spaces, to the greatest extent possible. However, green space typically
equates to an increased irrigation water demand. Using native vegetation will help reduce
landscape demand since the plantings are able to survive within the local climate. Another
factor affecting landscape water demand is vegetation density. Densely planted trees with
more leaf cover will lose water faster than less dense plantings. The immediate
environment in which vegetation is planted also has a significant effect on its water demand.
Vegetation planted in large green spaces will maintain an average microclimate as in a
natural setting. Plantings in a cool setting with shading from buildings or tree canopy cover
will have a lower water demand since they will lose water more slowly. However, vegetation
plantings in urban settings such as street tree planters will lose water more quickly due to
the warmer microclimate. Careful consideration to these landscape water demand factors
should be taken when designing a landscape to achieve maximum water efficiency.
The non-potable water demand was estimated based on the recommended land use
concept in the Port Whitby Sustainable Community Plan, with a focus on landscaped areas
that are proposed as well as existing areas that will be maintained. A baseline irrigation
demand has been calculated based on a number of factors, such as:
•
Landscape area
•
Irrigation efficiency
•
Landscape efficiency
Landscape area in Port Whitby was estimated to be 64ha, including the 19ha of the Iroquois
Park Sports Center and the 38ha of the proposed Harbor Green complex. Baseline
irrigation efficiency has been assumed to be 60%. Landscape efficiency was determined
based on three factors: species (Ks), density (Kd), and microclimate (Kmc). Baseline
landscape efficiency calculations were performed using values for a landscaping scenario
which represents a relatively common landscape design (Landscape Efficiency, KL = Ks + Kd
+ Kmc = 0.60). In combination with the landscape efficiency value, a monthly baseline
evapotranspiration rate, provided by the International Water Management Institute (IWMI),
was used to determine the baseline water demand for the overall landscaped area within
the Study Area, which was calculated as 682,000m3/year.
In addition to landscape demand, water features (e.g., wet ponds, fountains) contained
within the site will experience evaporation during warmer months of the year. Frequent
rainfalls may replenish the permanent pond volumes, but during times of drought, the water
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levels may need a supplementary water source. Therefore, an additional water demand of
70,000m3/year for water feature replenishment was incorporated into the overall water
demand.
Using water efficient landscape design can reduce the irrigation demands by 66% by using
xeriscaping principles, native species, and high efficiency irrigation systems with climateresponsive automated controls.
Overall, the water efficiency and conservation measures are expected to reduce the
baseline potable water demand for Port Whitby by 51%.
Figure 16a. Baseline vs. design water demands on a monthly and annualized basis.
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Figure 17b. Baseline vs. design water demands on a monthly and annualized basis.
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Financial Feasibility
Each of the conservation and efficiency strategies outlined above will have initial
construction or start-up costs, but will be expected to recover these costs and begin
achieving monetary savings after a payback period. A full financial analysis would include
not only these economic values, but also the environmental and social benefits that would
begin immediately after implementation, which can also be monetarized through a detailed
analysis that would be beyond the scope of this report.
For instance, using the 2010 billing rates, an average household in Whitby using 449m3/yr
of potable water (billed quarterly) would see an annual savings of $360 (or 46%) if their
consumption was reduced by 51% to 229m3/yr through conservation and efficiency. As
water and sewer rates increase, these savings will become even more pronounced.
There is a large number of case studies in which water efficiency and conservation
measures resulted in significant water usage reductions, with their associated monetary
benefits to both the municipality and end users. For instance, the American Water Works
Association did a household water use study to compare indoor water use rates for a single
family home with and without conservation measures, and found that a savings of 31% was
achieved.
Table 4. Residential water use for a single family home with and without conservation28.
Another study compared the water use of a typical 2.7-person household with a series of
fixtures with variable flow rates. The potential water savings from efficient fixtures are quite
dramatic, with overall reductions of 39% with respect to a conventional design with
replacements of only the toilets, showerheads, and faucets.
28
AWWA WaterWiser, Household End Use of Water Without and With Conservation, 1997. DRAFT
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Table 5. Water demand comparison for varying fixture efficiencies29.
Case Study: Region of Durham Efficient Community, Ontario, Canada30
A yearlong study conducted in 2006-2007 involving 175 homes in the Region of Durham
demonstrated significant savings in water, electricity, natural gas, and CO2 emissions.
Approximately half the homes received upgrades (efficient clothes washers, dishwashers,
toilets, showerheads, fridges, and landscape packages), and the other half served as a
control group. The average water savings in the study group with respect to the control
group were 132 L/day per household, or 22.3% of their consumption. Based on all the
savings achieved, a payback period of 3.4 years was calculated to cover the cost of the
upgrades. The project was conducted with support from Natural Resources Canada
(NRCan) and the Federation of Canadian Municipalities (FCM).
Table 6. Annual cost savings in study homes.
1.4.2
Rainwater Harvesting
Because of the high and consistent precipitation that Whitby receives throughout the year,
there is an opportunity to use rooftops and other areas to collect rainwater, which can be
stored in tanks and treated for use in irrigation, non-potable, agricultural, and municipal
systems. These include public parks, landscaped areas, water features, community
gardens, municipal street-cleaning, and firefighting needs.
29
30
Amy Vickers, Water Use Efficiency Standards for Plumbing Fixtures: Benefits of National Legislation, 1990. Veritec Consulting Inc., Region of Durham Efficient Community Final Report, 2008. DRAFT
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Benefits
Implementing a rainwater harvesting scheme for Port Whitby would result in the following
benefits:
• Decreased potable water demand by 9%
• Reduced stormwater runoff from the site by capturing approximately 10% of the
annual precipitation falling on the site
• Decreased hard infrastructure requirements for stormwater management and water
utilities, as rainwater harvesting will reduce peak flows
• Realization of energy savings through reduced water treatment and transport
• Greater resilience to climate change by decreasing site runoff and storing water for
use between precipitation events
Technical Feasibility
Rainwater harvesting systems are implemented in a wide variety of contexts, from simple
garden collection barrels to more sophisticated treatment and storage systems. A more
formal design typically requires the components outlined in the table below.
Table 7. Elements of a complex rainwater harvesting system.
Element
Drainage collection
system
Preliminary
treatment system
Coarse filtration
Storage
Overflow
Top-up connection
Secondary
treatment
Distribution
system
Description
Gutters, outlets, and downpipes to collect runoff from roofs or from
paved areas where suitable
If required to remove pollutants from roads or parking lots. This
could also include a first-flush diverter or roof washing system.
Either in-pipe or in-line filters
Tank with cleaning access, typically at lowest building level
(although a high level secondary tank can be installed for gravity
distribution)
For flood storage; can lead to a sewer, infiltration basin, or other
SWMP
Either to the storage tank or the distribution pump
Optional fine filtration and disinfection (only where required, as this
significantly increases overall energy demand)
Gravity or pressure pipeworks leading to the distribution network to
supply the design uses (e.g., toilets, washing machines, irrigation)
For a development on the scale of Port Whitby, there are two main approaches to rainwater
harvesting to be considered: either centralized, or on an individual building-level, as shown
in the figures below.
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Figure 18. Centralized, collecting from various buildings on-site vs. individual building-level.
There are additional challenges associated with rainwater harvesting design in cold
climates. However, these can be successfully addressed by following these guidelines:
•
Rainfall Patterns: generally, cold climates receive a fair amount of rainfall. However,
precipitation during winter months typically falls in the form of snow or ice. In the
coldest climates, the design will need to account for snowfall and snowmelt patterns
(both in volume and timing).
•
Storage Tank Location: if the storage tank is located outside, there are some key
issues to review. For example, if the tank is above ground, the water in the tank
may be subject to freezing during winter months. Providing heat to the tank is a
possibility, but there is additional energy required. By providing the storage tank
underground, consideration needs to given to the frost depth in the area, as the tank
should be installed below the specified frost depth.
•
Consideration for End Use: in colder climates, consideration will need to be given to
the potential deficit in rainwater during winter months for non-potable uses in the
building because of snow accumulation. If the end use is for irrigation there are two
design considerations:
•
•
DRAFT
Irrigation will not occur during the winter season. If water is collected on
paved surfaces which will be salted, the salt may be detrimental to the
growth of plants. A salt sensor can be used to monitor the rainwater and
alert maintenance staff of high levels in salt content. Pre-treatment
strategies such as manufactured hydrodynamic separators, filtration
techniques, sedimentation basins and catch basin sumps may help to
reduce the road salt loading to the tank.
If the rainwater is used for irrigation only, then one design/operational
feature to include would be a valve or gate to close off the system during
the winter season and reopen prior to the irrigation season. The closing of
the system during the winter season would also provide an opportune time
to maintain and disinfect the system, if necessary.
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Figure 19. Schematic of a rainwater harvesting system used for irrigation in a cold climate.
For rainwater harvesting storage systems, it is important to provide adequate maintenance
access using manholes and chambers. The system should be inspected for clogging of the
inlet and outlet, as well as any trash, debris, sediment or standing water. Structural
components must be inspected for cracking, subsidence, spalling and erosion. Inspections
should take place at least four times annually and after a major storm event. Sediment or
debris should be removed using a vacuum truck and repairs must be made to any structural
components with damage.
For Port Whitby, the proposed rainwater harvesting storage scheme accounts for seasonal
variability in precipitation, evapotranspiration rates, and landscape demands. A series of
under- and above-ground tanks will be used to store the water. Since not all proposed
buildings will be suited to rainwater harvesting, only about 28% of the total rainfall volume
that lands on the site can be captured. In order to optimize the amount of rainwater
captured to meet the water demands it can be used for, the design storage volume for
rainwater harvesting was set at approximately 10,000 m³. This volume is a tradeoff between
the savings that can be realized by meeting approved demands with rainwater, and the cost
and land area required to install the system. Area-wide irrigation and water feature demands
will be reduced by two-thirds, which will translate to an overall reduction for Port Whitby of
5%.
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Figure 20. Annual rainwater harvesting balance.
Finally, it is important to note that if harvested rainwater is to be used for any potable
applications, appropriate permissions will need to be secured from the Region of Durham,
which is responsible for all water and sewer infrastructure used in the Town of Whitby. All
potable water must meet the requirements of the Safe Drinking Water Act (SDWA) and the
Ontario Drinking Water Quality Standards (ODWQS). Water and sanitary sewer systems are
subject to the standards of the Ontario Building Code.
Financial Feasibility
The main capital costs associated with rainwater harvesting are for the collection and
treatment system, the storage and overflow tanks, and the distribution system. Additionally,
consideration must be given to the operations and maintenance costs associated with the
system, which will include pump maintenance, filter cleaning, tank cleaning, etc.
Some of the most commonly used tank materials are presented in the table below along
with their costs, available sizing, and general comparison.
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31
Figure 21. Tank material costs for a range of tank sizes .
Cost range (US $ / m3) Tank Material Size range (m3) Comments Fiberglass $ 130 $ 530 2 Concrete $ 80 $ 330 40 Polyproylene $ 90 $ 260 2 Can last for decades without deterioration; easily repaired; can be painted Risk of cracks and leaks but these are easily repaired; immobile; smell and taste of water sometimes affected but the tank can be retrofitted with a 3,800 plastic liner Durable and lightweight; black tanks result in warmer water if tank is exposed to sunlight; clear/translucent 40 tanks foster algae growth 80 Wood $ 530 3 Aesthetically pleasing, sometimes preferable in public areas and 190 residential neighborhoods Welded Steel $ 210 $ 1,060 120 3,800 Durable Using the data on concrete tanks and other available unit costs, we have developed a
simplified cost estimate for a series of rainwater harvesting systems that captures water
from 75% of Port Whitby’s roofs and 25% of park areas.
Table 8. Simplified rainwater harvesting system costing32.
Element
Metal Tank
Galvalume
Gutters
Sand Filter
Shallow Well Jet
Pump
Pressure Tank
Cartridge Filter
UV Light
Disinfection
TOTAL
31
32
Dimension(s)
508m3
50m
Unit Cost
$75,000
$1,500
Qty.
20
5
Total Cost
$1,750,000
$7,500
NA
NA
$2,500
$1,000
5
10
$12,500
$10,000
NA
NA
NA
$1,000
$100
$1,000
10
10
10
$10,000
$1,000
$10,000
$1,801,000
Texas Manual on Rainwater Harvesting, 3rd Edition, 2005. Texas Manual on Rainwater Harvesting, 3rd Edition, 2005. DRAFT
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A simplified payback calculation is presented below33:
Overall, the annual water bill savings will be $92,954. Thus, a simple payback period would
be:
This is a very simplified approach and should not be used for design. It does not include any
financial incentives that may be available for using rainwater harvesting, nor does it take into
account maintenance costs or the cost of a comparable irrigation system. It also considers a
level water service cost, whereas the recent trends for the region show substantial annual
increases. Nonetheless, it demonstrates that a rainwater harvesting system can pay for
itself within a reasonable timeframe.
Case Study: New Songdo City Central Park, South Korea
Constructed on reclaimed land along Korea’s Incheon waterfront, Songdo Central Park
forms the focal point of Songdo International Business District, a new business gateway to
northeast Asia. The sustainable park has been designed to echo the diverse indigenous
landscapes of the Korean peninsula, and features two boat houses, two foot bridges, a
visitor’s center, a children's play area, and an extensive canal system and a water taxi route,
among other amenities. Arup's design scope on Songdo Central Park included the canal
system, a three-level underground parking garage, drainage and utility design, pavement
analysis, lighting, rainwater harvesting for sustainable irrigation, and a remediation strategy
geared toward creating a plantable landscape on a platform of sea-dredged soils.
As the consultant in charge of hydraulics, hydrology, maritime, civil and geotechnical
engineering, Arup had to balance several, sometimes conflicting, drivers. From an aesthetic
standpoint, the park needed to reflect Korea’s varied landscapes, and the canal system
needed to meld seamlessly into all of these diverse physical settings. Equally important was
ensuring that the canals were constructible, durable and efficient, and that the canal waters
met strict water quality and sustainability criteria.
After evaluating several potential water sources for the canal system, from rainwater to
groundwater to potable, Arup’s engineers determined seawater to be the most sustainable
water source. While seawater was plentiful and locally available, it did bring with it certain
challenges, including red tides. Caused by plankton blooms, these discolorations can kill
fish and lead to inferior water quality and odours. To counteract these issues, Arup
designed an intake treatment facility capable of flushing the canal with large volumes of
33
Based on 2010 billing rates for Durham Region, http://mddurham.com/extcontent.asp?nr=departments/finance/water/howabill.htm&setFooter=includes/finance
waterfooter.inc#rates. DRAFT
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fresh seawater using the Danish Hydraulics Institute’s MIKE 11 software. The intake system
was designed to provide flexible flow rates to adapt to changing environmental conditions.
To avoid sediments from accumulating in the canal system, screening, self-cleaning depth
filters, media filtration and backwash treatment were used, and the use of environmentally
hazardous chemicals was avoided to treat the water. The park was opened to the public in
August of 2009 and serves as the centerpiece of 1500-acre New Songdo City development.
Figure 22. Rainwater storage installation for New Songdo City Central Park.
1.4.3
Greywater Reclamation
After minimizing potable water demands through conservation, efficiency, and simple
treatment for rainwater harvesting, further reductions can be achieved through greywater
reclamation. A separate greywater plumbing system can be implemented in commercial and
residential buildings, which will carry untreated flows from approved sources (e.g.,
showers/tubs, clothes washing machines) to be treated appropriately onsite for toiletflushing, irrigation, and other non-potable uses. Not only does this reclaimed water reduce
the burden on the public potable water system, but it also diverts wastewater flows that
would otherwise require treatment at a centralized plant.
Building water fixtures are typically divided into greywater and blackwater sources as
follows:
DRAFT
•
Sources of Greywater:
o Showers
o Bathtubs
o Bathroom sinks
o Clothes Washers
•
Sources of Blackwater:
o Water Closets
o Urinals
o Dishwashers
o Kitchen Sinks
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Due to high drinking water quality standards, reclaimed water is typically not used for
potable uses such as drinking, showering and washing. However, a relatively high
percentage of the personal water demand comes from flushing toilets. Traditionally, the
wastewater generated from all uses is piped to a wastewater treatment plant, where
pollutants are removed and treated effluent is discharged into a body of water. Instead, the
treated effluent can be used as a resource, and used for uses which do not require the
highest quality standards. The reclaimed water can then be distributed throughout the
community via a dual distribution system (i.e., one water main for potable and a second for
non-potable use). In certain cases, it is feasible to treat reclaimed water back to potable
water standards.
Figure 23. Reclaimed water signage (left) and distribution system using purple pipes (right).
Like harvested rainwater, reclaimed water can also be used to supplement permanent water
pools in stormwater features. Reclaiming water for non-potable use will greatly reduce the
water demand on the local supply, and decrease the effluent load to Lake Ontario, thereby
helping to mitigate high nutrient levels from wastewater discharge, as well as other
pollutants that are difficult to treat (e.g., pharmaceuticals, endocrine disruptors).
Benefits
A greywater reclamation strategy implemented in several of the large buildings and
residential developments in Port Whitby would yield the following benefits:
• Reduce potable water demands by 23%
• Reduce the wastewater volume from buildings that is sent to the municipal system
by 40% through the conservation and efficiency strategies discussed previously,
and the resultant flow volume will be reduced by a further 75% through greywater
reclamation
• Limit the discharge of treated effluent to Lake Ontario, which is sensitive to nutrient
and trace pollutant loadings
Technical Feasibility
All building uses throughout the Study Area contribute to the overall wastewater discharge.
A portion of this wastewater could be treated and reused again within the buildings for nonpotable uses (toilets, washing machines, etc.). Based on projected water demands from the
various building uses, it is estimated that 85% of the water demands from the various
building uses is for non-potable applications (e.g, toilets, irrigation). This volume of water
could be supplied using reclaimed water.
In addition to reusing water for non-potable building uses, if there is any excess treated
wastewater effluent, it can be allotted for reuse to supplement irrigation demands of the
open spaces, including public parks, residential lawns, community gardens, and open space
associated with buildings. Similar to the landscape demand for rainwater harvesting, the
demand associated with the lawns and fields was calculated based on the overall land area
of these spaces.
DRAFT
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The following table summarizes the site-wide water demands that can be met using
reclaimed water, with 921m3/day being treated. Treating reclaimed water to potable
standards was not considered given the high non-potable demands, along with the many
regulatory and public perception challenges associated with using reclaimed water for
potable purposes.
Table 9. Water demands that can be met by onsite sources, including reclaimed water and
rainwater harvesting.
DEMAND
Potable
(m3/day)
Non‐
Potable
(m3/day)
SUPPLY
Reclaimed Rainwater Non‐Potable WSP
Water
Harvesting Demand Met By 3
(m /day)
Onsite Sources
(m3/day)
(m3/day)
Commercial
569 1,579
1,558
590
‐
37.3%
Institutional
15
18
66 7
‐
37.3%
Recreational
35
77
188
29
‐
37.3%
Residential
1,682
791
2,178
296
‐
37.3%
‐
685
197
‐
489
71.3%
90
90
116
‐
64
71.3%
2,390 3,240
4,302
921
553
45.5%
Irrigation
Water Features
TOTAL
All developments in the Province of Ontario must comply with the regulations of the Ministry
of the Environment (MOE). The central piece of legislation is the Ontario Water Resources
Act. The normal level of treatment required for municipal and private wastewater plants
discharging to surface waters is secondary treatment, although higher levels of treatment
may be required based on site-specific assessments34. It is assumed that the effluent from
the water reclamation treatment system(s) within Port Whitby will meet or exceed these
effluent guidelines. Water and sanitary sewer systems must also meet the standards of the
Ontario Building Code.
34
MOE, 1994, Levels of Treatment for Municipal and Private Sewage Treatment Works Discharging to Surface Waters DRAFT
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Table 10. MOE Effluent Criteria.35
In the area of water reuse, the draft Canadian Guidelines for Household Reclaimed Water
for Toilet and Urinal Flushing (2007) have been developed by Federal Provincial Territorial
Committee on Health and the Environment, which will be eventually superseded by formal
guidelines. The guidelines outline a risk assessment based approach to water quality
standards for reclaimed wastewater. Canada Mortgage and Housing Corporation has
implemented several household-level scale water reuse projects. A selection of these and
other reuse projects are included in the table below to demonstrate the feasibility of this kind
of system.
35
MOE Procedure F‐5‐1, Determination of Treatment Requirements for Municipal and Private Sewage Treatment Works Discharging to Surface Waters DRAFT
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Table 11. Water reuse guidelines.36
To maximize the efficiency of the treatment system, wastewater is usually separated into
two streams: blackwater and greywater. Typical characteristics of blackwater and greywater
are outlined below37:
•
Blackwater
o Biological Oxygen Demand (BOD) 80 gpcd (grams per capita-day)
o Total Suspended Solids (TSS) 90 gpcd
o Total Kjeldahl Nitrogen (TKN) 13 gpcd
•
Greywater
o BOD 25 gpcd
o TSS 18 gpcd
o TKN 1 gpcd
Blackwater is collected in the sanitary system and is piped to a treatment system. The
resulting effluent from the blackwater treatment is then piped back into the building
greywater system and is collected with the building’s greywater for further treatment.
36
Water Reuse in Canada: Opportunities and Challenges, by Exall, K., Marsalek, J., and Schaefer, K., National Water Research Institute, Environment Canada, 2006. 37
Asano, Takashi (2007) Water Reuse: Issues, Technologies and Applications. Metcalf and Eddy DRAFT
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The wastewater treatment technologies listed in the table below are examples of the types
of systems that could be considered for either greywater or blackwater treatment.
Table 12. Wastewater treatment technology comparison.
System
Advantages
Membrane BioMost compact system
Reactor (MBR)
Most scalable to future capacity
Fully automated/Low maintenance
Accepts high pollutant load
Conventional
Most common system type
Activated Sludge
(RAS)
Rotating Biological
Accepts high pollutant load
Contactor (RBC)
Living Machine®
Visual amenity – can be showcased
Quiet & low cost operation
Disadvantages
Higher level of operator training
Higher energy use for treatment
Higher energy use for mixing
Higher energy use
Potential for odor/noise
High level of maintenance
Larger footprint/system size
Insufficient water quality
A preliminary analysis of a wider spectrum of treatment technologies was carried out to
ensure that proper consideration is given to those that might meet the needs of Port Whitby.
An overall weighted score is calculated for each one, based on the following criteria:
Figure 24. Wastewater treatment design criteria relative weights.
Given these criteria, the technologies in Table 13 emerged as potentially viable alternatives.
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Table 13. Preliminary ranking of wastewater treatment technologies based on project
requirements.
Technology
UV
SBR
RO
MF/NF/UF
MBR
CAS
Wetlands
Footprint (m²)
O&M Cost (per year)
16 $
63,820
1,392 $
49,531
Design Flow as % of Max. Influent Effluent for Capacity
Reuse?
5 $ 2,401,552
4% Yes
Nutrient and BOD removal
Robustness Overall Weighted Score
N: ; P: ; BOD: 0
Medium
70%
N: 0.2; P: 0.15; BOD: 0.9
High
55%
43% Yes
N: 0.85; P: 0.85; BOD: 0.9 High
50%
43% No
N: 0; P: 0.65; BOD: 0.35
Medium
45%
N: ; P: 0.68; BOD: 0.99
High
45%
1646% No
6,328 $
120,173
2 $
818,355
1,303 $
192,657
0% No
N: 0.2; P: 0.15; BOD: 0.9
High
40%
549,523 $
30,435
43% No
N: 0.7; P: 0.3; BOD: 0.7
Medium
35%
0% Yes
In addition, emerging technologies such as algae photo-bioreactors for wastewater
treatment may become available by the time of the detailed design phase. These should be
evaluated alongside the technologies listed above.
Financial Feasibility
A membrane bioreactor (MBR) treatment plant technology was considered for the financial
feasibility analysis due to its compact size and reliable operation across a large spectrum of
influent characteristics. It was also one of the top technologies that emerged from our
preliminary technical feasibility analysis. It can be seen in the figure below that as the
population served increases, efficiencies of scale allow for a reduced cost per unit volume of
treatment (at least for the population ranges considered).
Figure 25. MBR wastewater treatment plant preliminary costing38.
The separate plumbing system recommended for dedicated greywater and reused flows
would require an initial investment, but some of the cost would be recovered over time due
to the water and energy savings it would yield.
Case Study: Beddington Zero Energy Development, Hackbridge, London, UK
The “BedZED” mixed use sustainable community was completed and occupied in 2002. A
total water strategy was implemented which provides treatment for greywater that can be
reused for toilet flushing. The main treatment plant is housed in an elevated greenhouse,
incorporating hydroponics where plants on the roof of the tanks reduce the nitrogen and
phosphorous content of the water. Overall, a 58% reduction in water use was achieved
through water reuse and rainwater harvesting.
38
Based on consultations with GE regarding their DRAFT
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Figure 26. Beddington Zero Energy Development (BedZED).
Case Study: Irvine Ranch Water District, Irvine, California39
The Irvine Ranch Water District (IRWD), located in Irvine, Calif., is one of the pioneers in
water reclamation through a dual piping system. IRWD operates a tertiary treatment plant
and a totally separate distribution system consisting of 245 miles of pipeline, eight storage
reservoirs and 12 pump stations for reclaimed water. Reclaimed water now makes up 20
percent of IRWD's total water supply and provides irrigation for 80 percent of all commercial
and community landscapes, including parks, schools, golf courses and open space. Over
5,650 acres of landscaping are irrigated with reclaimed water. A few estate-sized residential
lots also use the water for irrigation and most water features are filled with reclaimed water.
Reclaimed water has also been used in industrial applications. A carpet mill estimates they
save from 500,000 to 1 million gallons per day of potable water by using reclaimed water in
their production process.
In addition to outside use, IRWD has received health department permits for interior use of
its reclaimed water. Reclaimed water is currently used for toilet flushing in the district's
offices as well as several high-rise office buildings. Potable, or drinking, water demand has
dropped by as much as 75 percent in these buildings due to reclaimed water use.
1.4.4
Multifunctional Green Infrastructure
Natural treatment systems for stormwater and wastewater can reduce both upfront and
operation and maintenance (O&M) costs over the lifetime of the system with respect to
traditional manufactured and/or centralized systems. In addition, they provide aesthetic and
habitat benefits, as well as valuable educational opportunities.
Benefits
As a decentralized approach to wastewater treatment, a constructed wetlands system can
bring about the following benefits:
• Reduce the wastewater volume sent to the municipal system
• Reduce energy demand through natural treatment vs. conventional treatment
• Make productive use of available land within the Study Area that is not suitable for
buildings by accommodating the constructed wetlands
• Provide habitat for wetland flora and fauna
39
This case study is a direct quote of the article by David Crane, “Case study in the use of reclaimed water systems: Irvine (Calif.) Ranch Water District” DRAFT
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•
Greater ease of adaptation than a centralized wastewater treatment plant to
changes in the population it is serving or other factors that affect its performance, as
illustrated in the figure below
Figure 27. A decentralized wastewater system can adapt more flexibly than a centralized
40
wastewater treatment plant to changes in demand over its expected life .
Technical Feasibility
Constructed wetlands can be used to perform two functions in wastewater treatment:
secondary or tertiary treatment. Constructed wetlands for secondary treatment are
designed to remove TSS, BOD and FC. Tertiary wetlands are designed to remove
nutrients, metals and chemicals.
Figure 28. Pollutant Removal Pathways in Constructed Wetlands.
40
Rocky Mountain Institute, http://www.rmi.org/rmi/Library/W04-21_ValuingDecentralizedWastewater
. DRAFT
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Based a typical design as outlined in the MOE’s 2003 Stormwater Management Planning
and Design Manual, along with other relevant design guidance, the total area required for
constructed wetlands to treat the stormwater from a 27ha watershed within Port Whitby was
determined to be approximately 0.9ha. In order for a wastewater wetland to serve 10% of
the residential buildings, it would require approximately 0.8ha of land.
Figure 29. Typical constructed wetland elements in plan and profile41.
There are two types of constructed wetlands commonly used for secondary treatment: free
water surface (FWS) wetlands and vegetated submerged bed (VSB) wetlands.
Free Water Surface Wetlands consist of one or more shallow basins with a liner to prevent
infiltration. The liner is required to prevent contamination of groundwater supplies with
partially treated wastewater. FWS typically have three zones: a fully vegetated zone 1, an
open water zone 2 with submerged vegetation and a fully vegetated zone 3. If greater
hydraulic retention is required additional zones may be added by alternating open water and
vegetated zones with the last zone being a vegetated zone.
41
California Stormwater BMP Handbook, TC‐21, 2003. DRAFT
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Figure 4.6: FWS Wetland Treatment Zones42
FWS wetland size may be estimated by using typical areal loading rates for biological
oxygen demand (BOD) and total suspended solids (TSS). The table below lists areal
loading rates for FWS wetlands with significant open water.
Table 14. Areal loading rates43.
Parameter
BOD
TSS
Areal Loading
(kg/ha-d)
Effluent Conc.
(mg/L)
60
45
50
30
30
<20
30
<20
Low temperature can cause a decrease in the removal rates of some constituents, such as
nitrogen and phosphorous. However, removal of BOD and TSS is less affected by
temperature because removal is achieved primarily by physical methods such as
flocculation and sedimentation.
Algae growth can be detrimental to wetland performance because it blocks sunlight,
preventing lower level plant growth and lowering dissolved oxygen (DO). Open, unshaded
water, near wetland outlets can lead to season algae bloom. Algae control would be a
design consideration because low DO levels are typically of concern in waterbodies like
Pringle Creek and Whitby Harbour.
In addition to providing physical treatment, the proposed constructed wetlands could also be
designed to provide biological treatment. This requires a Schedule C Class EA, under the
Municipal Class EA44.
Vegetated submerged bed (VSB) wetlands, also known as subsurface flow wetlands,
consist of a vegetated basin with a gravel base surrounded by an impermeable liner.
42
EPA Constructed Wetlands for Treatment of Municipal Wastewater EPA Constructed Wetlands for Treatment of Municipal Wastewater 44
MOE, Stormwater Management Planning and Design Manual, 2003. 43
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Figure 4.7: Vegetated Submerged Bed Wetland
45
The main difference between FSW and VSB wetlands is that VSB wetlands have no
standing water. This eliminates the risk of breeding mosquitoes and other vectors and
minimizes the human health risk. Also in comparison to FSW wetlands, VSB wetlands
provide greater thermal insulation allowing them to operate at lower temperatures. VSB
wetlands are generally smaller systems, typically handling less than 40,000 gallons per day
(GDP). At approximately 60,000 GPD, VSB wetlands become an uneconomic option when
compared to FSW. VSB’s are not recommended for Phosphorous removal. Because of the
project scale and nutrient concerns, VSB wetlands are not a recommended option.
Polishing wetlands are used for tertiary treatment and can remove nutrients, chemicals and
trace metals such as Cadmium, Chromium, Iron, Lead, Manganese, Selenium and Zinc.
Polishing wetlands follow some form of secondary treatment and are often used before
discharging to estuaries or other particularly sensitive water bodies. Polishing wetlands
generally are free water surface wetlands. Similar to secondary FWS wetlands, they are
sized by the controlling pollutant based on influent characteristics and treatment goals.
Tertiary or polishing wetlands are often used as environmental education centers. Public
visitation is not appropriate for secondary treatment wetlands, because there is significant
risk of dermal contact and communication of disease, especially in near the inlet where the
water is essentially primary effluent.
Financial Feasibility
Constructed wetland treatment systems are financially competitive with other treatment
options, and can provide a significant advantage over time due to their low operations and
maintenance requirements. A comparative study conducted in Belgium demonstrates this,
as highlighted by the figure below. Based on their data, a wastewater wetland serving
approximately 1,500 persons would have an up-front capital cost for installation of
approximately $500/person. The ongoing operational costs would only be approximatey
$10/person-year.
45
EPA Technology Fact Sheet Wetlands: Subsurface Flow DRAFT
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Figure 30 Capital cost (left) and operation and maintenance (O&M) cost (right) per person
equivalent for wastewater systems in Belgium based on five years of data (note that “reedbed”
is equivalent to constructed wetlands)46.
Case Study: Free Water Surface Constructed Wetlands (Arcata, California)
Arcata is located on the Northern coast of California and has a population of around 15,000.
In 1949, the community constructed a primary treatment plant which discharged effluent to
Arcata Bay on the Pacific Ocean. In 1957, oxidation ponds and chlorine disinfection were
added. A 1974 law requiring communities to prove the quality of wastewater before
discharging into estuaries was passed. This prompted the community to test the
performance of a pilot scale constructed wetlands.
Figure 4.18: Arcata Treatment Wetlands47
46
Magliaro, J., Lovins, A. 2004. Valuing Decentralized Wastewater Technologies: A Catalog of Benefits, Costs, and Economic Analysis Techniques. Rocky Mountain Institute. http://www.rmi.org/rmi/Library/W04‐21_ValuingDecentralizedWastewater 47
Humbolt State Environmental Resources Engineering DRAFT
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The city proposed and tested a novel form of constructed wetlands composed of densely
vegetated cells followed by enhancement marsh cells with a large percentage of open water
for polishing. The National Pollutant Discharge Elimination System (NPDES) permit for the
project allowed 30 mg/L BOD, 30 mg/L TSS, pH from 6.5 to 9.5 and 200 CFU/100mL fecal
coliforms.
Because the enhancement marshes are used as recreation and habitat areas, disinfection
was required before the marshes. Final disinfection and dechlorination is required before
discharge to Arcata Bay.
The full scale treatment wetland is divided into three parallel cells and has a total design
flow of 2.9 MGD. Cells one and two have surface areas of 2.75 acres each and cell three
has an area of 2.0 acres. The operational water depth is approximately four feet. The
hydraulic retention time in these cells is 1.9 days. These cells were not designed for
nutrient removal. The enhancement marshes have a total area of 31 acres.
The long term performance of the system was tracked and the results are presented in
Table 4.7.
Table 4.7: Arcata Wetland System Performance48
1.4.5
Stormwater Management Practices
The design methodology for sustainable stormwater management in Port Whitby follows the
following hierarchy:
Figure 31. Approach to Sustainable Stormwater Management.
Preventative source control strategies focus on minimizing the amount of pollutants and
waste that enter into the stormwater management system. These include:
48
EPA Constructed Wetlands Treatment of Municipal Wastewater DRAFT
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•
•
•
•
•
Preventing trash and debris from entering the drainage system by providing trash
receptacles at key locations, and trash racks in stormwater management features
A regular program of street sweeping and litter collection
Pet waste stations in residential developments
Site design features to prevent and contain contaminated spills including knee
walls, berms, secondary containment areas, oil/water separators
Minimizing or eliminating the use of fertilizers and pesticides
Low impact development (LID) design will decrease runoff at the source (rather than end-ofpipe management), and also promote on-site infiltration and groundwater recharge. Several
LID techniques can be implemented to achieve this goal, such as:
•
•
•
Open Space and Landscaping
Reducing Impervious Surfaces
Time of Concentration Modification
Stormwater management practices (SWMPs), with an emphasis on natural systems, where
possible, are intended to ensure that both the waters discharged from the system meet
water quality requirements, and appropriate retention facilities will control discharge water
volumes to attenuate the peak flows associated with large storm events. It is estimated that
a minimum of 15ha should be devoted to implementing SWMPs. These could be integrated
into roads, public spaces, parks, and the open space system.
In cases where space is limited, underground manufactured stormwater management
devices should be considered to provide retention and treatment.
Examples of natural and manufactured stormwater management systems are included in
Figures 31 and 32.
Figure 32. Natural stormwater management practices.
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Figure 33. Manufactured stormwater management systems.
Benefits
A comprehensive stormwater management strategy for Port Whitby will lead to the following
benefits:
•
•
•
•
•
•
Enhanced water quality
Restoration of a more natural hydraulic regime, with benefits to Pringle Creek and
Lake Ontario
Use of stormwater as a resource on site, rather than simply a waste product
Reduced flooding
Replenishment of local aquifers through new high infiltration areas and recharge
zones
Reduction of the heat-island effect and prevention of thermal pollution to Pringle
Creek through tree plantings, surface water features, and underground detention.
Figure 34. Heat-island profile generated by the abundance of dark, impervious surfaces and
lack of vegetation typically found in highly developed areas.
Technical Feasibility
A sustainable development design implements measures to decrease the amount of
impervious surfaces by promoting open space, and including porous pavements and green
roofs. Our assessment considers each component of the recommended land use concept,
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and determines appropriate design options based on the parameters described previously.
The assessment is divided into the following components:
• Building-level
• Parcel-level
• Street-level
• Neighbourhood-level
Building-level strategies
On a building-level, the main strategies are green roofs and green walls. Green roofs can
transform large building roof areas into vegetated green space. Green roofs are capable of
absorbing rainwater that would ordinarily become runoff. When properly designed, green
roofs will have minimal potential for overtopping and flooding during extreme events. They
are used successfully in the Toronto area49. Similarly, green walls add aesthetic value to a
project and contribute to the evaporative cooling which reduces the urban heat island effect.
50
Figure 35. A sloped green roof landscaping and roof runoff comparison .
On a parcel-level, rain gardens and community gardens are proposed. These can be
irrigated with harvested rainwater and recycled greywater if there is excess supply.
Figure 36. A community garden in highly urbanized lower Manhattan.
49
50
MOE Stormwater Factsheets, 2001 Roofscapes, Inc. and Rain Gardens by Nigel Dunnett and Andy Clayden DRAFT
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Street-level Strategies
On a street-level, green streets incorporating bioswales, biofiltration planters, and porous
pavements are the predominant strategies proposed.
Bioswales consist of a soil bed planted with native vegetation above an underdrained sand
layer and are designed to convey and filter stormwater runoff. The following images present
an example of bioswales integrated within the street framework.
Figure 37: Bioswales.
Similar to bioswales, subsurface biofiltration planters consist of a soil bed planted with
native vegetation above an underdrained sand layer and are designed to filter stormwater
runoff. The planters are fully underground and are composed of a bioretention soil mix
within an enclosure cell. These planters, which can also incorporate tree pits, collect runoff
from the roadway via openings in the curb or drainage inlet connections. The image below
presents an example of biofiltration tree planters under construction.
Figure 38: Biofiltration Tree Planters.
In areas of high pedestrian traffic, consideration should be given to integrated sidewalk icemelt systems, which increase pedestrian safety and accessibility.
Figure 39. Integrated sidewalk ice-melt system.
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Porous pavements such as porous concrete, porous asphalt or porous paver systems can
installed instead of conventional concrete and asphalt. Porous pavements decrease
stormwater runoff by allowing rainwater to seep through the pores and infiltrate into
subsurface soils. Porous pavements typically cannot achieve the compressive strength
properties of conventional pavements; therefore the most practical applications for such
pavement surfaces are parking areas, pedestrian walkways, and roads with low traffic
volume. Furthermore, where possible, pavements can be eliminated altogether by
implementing structural grass paving. Structural grass paving grids provide the same
service as asphalt, but with significantly less impacts to stormwater runoff. It provides the
same runoff characteristics as a lawn, but has a high enough structural integrity to withstand
vehicle loads. Some grass paver grids are available in 90-100% recycled plastic. A
geotechnical investigation will reveal optimal locations on-site (based on soil types) to install
porous pavements.
51
Figure 40. Porous Concrete (left) and Porous Paver Roadway (right) .
Figure 41. Grass pavers52.
Neighborhood-level strategies
On a neighbourhood scale, the main strategies proposed include stormwater wetlands, wet
ponds, groundwater recharge areas, and prominent water features.
The discussion provided in a previous section on constructed wetlands for wastewater
treatment applies in the case of wetlands designed for stormwater treatment as well. Based
on our analysis of the pre-development watersheds, stormwater wetlands would require an
area of 0.80ha.
51
52
www.tececo.com and North Coast Stormwater Coalition www.grassypavers.com and www.boddingtons-ltd.com DRAFT
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Figure 42. Pre-development watersheds on the site.
Table 15. Watershed areas.
Watershed A (Yacht Club) B (Park) C (Rec Center) D (Rail/Hwy) E (Open Channel) F (Core) G (East) H (Brookfield) Total Drains to Whitby Harbour Whitby Harbour Whitby Harbour Ditches Open Channel Whitby Harbour Pringle Creek Whitby Harbour Pre‐development Area (m2) 99,773 230,682 218,918 174,220 229,923 150,769 480,743 141,291 1,726,318 Most communities surrounding Lake Ontario extract their water supply from the lake.
Developments further from the lake can receive water from individual wells or by pumping
from underground aquifers. Regardless of the location or means of acquiring water, it is
important to replenish the local supply as much as possible. Pumping water from
underground aquifers will, over time, diminish the water supply and cause necessary drilling
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deeper and deeper to reach the underground water surface. Depleting aquifers can have
deleterious effects on bodies of water, such as Lake Ontario, because rivers and lakes often
receive a portion of their volumes from underground baseflow. Decreased baseflow can
reduce water volumes in such bodies of water.
Despite strategies that reduce, reuse, and reclaim water throughout the development, a
significant portion of the water supply will come from local water distribution systems.
Therefore, water resources such as aquifers and lakes will be drawn down to provide such a
supply. In combination with depleting water resources, the increased impervious areas and
compacted soils from the development will prevent infiltration and groundwater recharge,
which occurs at a higher rate in a natural setting. In order to mitigate the depletion of water
resources, infiltration practices should be implemented where possible. Infiltration basins
(underground or above-ground) and bioretention systems are two common recharge
practices. Infiltration basins are more efficient in providing groundwater recharge since the
vegetation in a bioretention system will absorb a significant portion of runoff. Reducing
water demand and recharging groundwater can significantly decrease the rate at which a
water resource is depleted.
Prominent water features throughout the project area bring a sense of connectedness and
transparency to the community, as well as serving aesthetic, recreational, educational,
habitat, and stormwater management purposes. Examples of this include fountains, ponds,
and canals.
Figure 43. A variety of water features.
Regulatory framework
New regulations have been promulgated that require additional actions to ensure that
source protections are implemented for Ontario’s water supply. The Town of Whitby is
located within the Credit Valley, Toronto and Region, and Central Lake Ontario Source
Protection Region, specifically in the Central Lake Ontario Source Protection Area.
All developments in the Province of Ontario must comply with the regulations of the Ministry
of the Environment (MOE). The Ontario Stormwater Management Planning Design Manual
(2003) recommends the implementation of Stormwater Management Practices (SWMP),
and includes design criteria and considerations for modifications to suit cold climates.
The Pringle Creek watershed is regulated as an enhanced treatment area because it drains
to Provincially Significant Wetlands (PSW). Thus, it is subject to the MOE enhanced “level
1” stormwater quality protection. Under the guidance of the Central Lake Ontario
Conservation Authority (CLOCA), stormwater management in Port Whitby must comply with
the local Watershed Management Plan and Watershed Studies. The Regulatory Storm is
defined as the greater of the 1 in 100 year design storm or Hurricane Hazel. Design storm
data is available from CLOCA, which can be used to calculate rainfall depths for the design
storms shown in the table below.
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Table 16. Rainfall depth for the Town of Whitby design storms.
Return Period (years)
Rainfall Depth
(mm)
2
5
10
25
50
100
0.25
16
23
28
33
38
42
1
25
35
41
49
55
61
Storm Duration, td (hours)
2
12
30
44
40
57
47
66
56
76
63
85
70
93
24
51
65
75
85
95
104
Based on this data, the rainfall intensity for the design storms in the Town of Whitby can
also be calculated, as shown in the figure below.
Figure 44. Rainfall intensity for the Town of Whitby design storms.
In addition, Lake Ontario has a Lakewide Management Plan (LaMP) that has been
developed jointly by Region II of the U.S. Environmental Protection Agency (USEPA),
Environment Canada (EC), the New York State Department of Environmental Conservation
(NYSDEC), and the Ontario Ministry of the Environment (MOE) (the Four Parties), in
consultation with the public53. Within Canada, the Canada-Ontario Agreement (COA)
supports the restoration and protection of the Great Lakes Basin Ecosystem, which includes
monitoring progress on elimination of harmful pollutants.
In light of these concerns, the SWMPs proposed will make a significant positive contribution
to the water quality and overall health of Pringle Creek and Lake Ontario. The results of
several studies on removal efficiencies of total suspended solids (TSS) and total
phosphorus (TP) are presented below. These also serve as proxies for other treatment
benefits, such as removal of total nitrogen (TN), heavy metals, total petroleum hydrocarbons
(TPH), heavy metals, etc.
53
Lake Ontario LaMP, http://www.epa.gov/glnpo/lamp/lo_2008/index.html DRAFT
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Figure 45. Typical removal rates of SWMPs.
Financial Feasibility
The USEPA conducted a study in 2007 that compared the cost between conventional
versus low impact development (LID) approaches. The results show that LID approaches
had a 15-80% lower capital cost through savings in grading, stormwater infrastructure, site
paving, and landscaping.
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Table 17. Cost Comparison between conventional and LID approaches.
Green streets provide not only environmental benefits, but economic benefits as well. A
green street will incorporate a combination of “green” techniques such as porous concrete,
porous pavers, and infiltration planting beds. Three street typologies were evaluated:
•
Traditional Street
•
“Light Green” Street
•
“Deep Green” Street
A traditional street is comprised only of impervious paving such as asphalt and concrete,
conventional catch basins, and an underground hydrodynamic separator to meet water
quality requirements. If desired, a combination of a traditional and fully green street may
actually reduce up front installation costs. This “light green” approach would include less
porous and more impervious paving, as well as fewer planting beds, than the “deep green”
scenario. For a fully green street (“deep green”) with paver sidewalks, frequent infiltration
planters and porous pavement street parking lane, the cost of installation can increase by
30%. However, the water quality treatment and storage capacities of the green street
SWMPs will reduce the costs of excavation and installation of SWMPs downstream. This
reduced cost can shrink the difference in (or completely eliminate) the gap between the cost
of deep green and traditional streets. Also, reduced maintenance may reduce cost over an
extended time period.
A cost estimate has been performed for a sample section of roadway to compare the cost of
a green street and a traditional street. The cost calculations were performed for a sample
roadway section 150 m (500 ft) in length with a 9 m (30 ft) roadway and 20 ft (6 m) wide
sidewalks. Sidewalks and roadways vary in each scenario as described above. The
estimates demonstrate that the deep green street costs will be about 33% higher than
traditional, while a light green street would reduce initial construction cost by 5%. The
following table summarizes the results of the cost estimates.
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Table 18. Green Street cost comparison.
Street Type
Construction Cost
Traditional Street
$ 360,000
Light Green Street
$ 341,000
Deep Green Street
$ 483,000
Given that there are approximately 155,000m2 of roadways within Port Whitby, the potential
benefits of implementing a light green or deep green street approach would be magnified. In
particular, we recommend that green street elements be considered for Brock St S, Watson
St W, and Henry St, which have been designated as “shared roads.”
A comparison of various SWMPs based on their upfront construction costs and annual
maintenance cost has been conducted, showing the following relative magnitudes.
Figure 46. Costs for construction and ongoing O&M for SWMPs.
Case Study: Southeast False Creek Constructed Wetlands, Vancouver, BC
The Southeast False Creek Olympic Village developed for the 2010 Winter Olympics was
built on 32ha of former industrial land and is now a mixed-use neighbourhood that is
certified LEED Platinum. It includes an innovative wetland system designed to treat the
stormwater that runs off the site, allowing the community to be disconnected from the City of
Vancouver’s storm sewer network. This freshwater wetland system was designed to
accommodate the flows resulting from a 100-year return period storm event, and during lowflow periods is augmented with reclaimed potable water from buildings in the
neighbourhood, ensuring that the habitat it provides remains viable year-round. There is a
dam at the downstream end of the wetland that allows the treated flows to spill over into the
receiving water body, False Creek, and prevents saline water from intruding into the
wetland.
To increase community access to the wetland, there is a children’s play park adjacent to the
wetland. Furthermore, the Southeast False Creek Neighbourhood Energy Utility uses
localized sewer heat recovery to generate electricity for use onsite. The project was made
possible in part due to special funding provided by the Federal Gas Tax Fund and the Green
Municipal Fund.
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Technical Study: Water and Wastewater
Figure 47. Stormwater wetland system in SE False Creek, with community access
features (image credit: Danny Singer).
Case Study: PlaNYC, New York, New York
New York City has developed a comprehensive sustainability plan for the city’s future called
PlaNYC. As part of the study of stormwater strategies for the city, they developed a
comparison on the basis of the cost per unit volume of water detention (see figure below).
Figure 48. Comparison of SWMPs based on cost per gallon of stormwater detention54.
54
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Case Study: NRDC City Comparison, USA and Canada
The Natural Resource Defence Council has developed a comparative study of the
progressive stormwater management strategies implemented in several major cities in the
USA and Canada. Their findings are summarized in the table below.
Table 19. NRDC city comparison.
Case Study: Grey to Green, Portland, Oregon
Portland has implemented a “Grey to Green” program, investing $50M USD over the period
2008-2013 to improve the water quality in their rivers. The program has set out the following
ambitious objectives:
•
•
•
•
•
•
Add 17.4 hecatares of ecoroofs
Plant 83,000 trees
Construct 920 green street facilities (streetside planters and curb extensions)
Restore native vegetation and control spread of invasive species
Protect 170 hectares of public lands (preserving watershed functions and
floodplains)
Replace 8 culverts that block fish passage
To date, the city sustainable stormwater management plan has reduced CSOs by 72%.
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Technical Study: Water and Wastewater
Figure 49. Grey to green strategies implemented in Portland, Oregon.
1.5
Summary of Recommended Strategies
Based on the research and analysis contained in this Technical Study, as well as other
considerations such as the feedback received through the public and agency consultation
process and the opportunities for synergies with other sustainability themes, the following
recommendations are made in the Port Whitby Sustainable Community Plan (SCP) with
respect to water and wastewater (these recommendations are elaborated in the SCP):
a) Limit potable water demand through conservation and efficiency measures.
b) Augment water supply through rainwater harvesting.
c) Design new developments to support the reuse of greywater.
d) Consider opportunities for using multifunctional green infrastructure, such as
constructed wetlands, for stormwater and wastewater treatment.
e) Minimize the extent of impervious surfaces in Port Whitby.
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