Water Balance, Quality & Efficiency for Low-Rise Residential Development

Toronto Green Standard Water Quality Icon

Development Features

  • Protect water quality during construction and demolition
  • Capture and manage rainfall to improve stormwater runoff and enhance resilience of infrastructure to extreme rainfall events
  • Manage and clean stormwater that leaves the site
  • Reduce demand for potable water through efficient fixtures and appliances and reusing non-potable water

Tier 1

WQ 1.1 Erosion and Sediment Control

Follow the Erosion and Sediment Control Guideline for Urban Construction during construction and demolition activities. (1)

Specifications and Resources

  1. Refer to the Greater Golden Horseshoe Area Conservation Authorities Erosion and Sediment Control Guideline for Urban Construction.

Tier 1

WQ 2.1 Stormwater Retention and Reuse

Retain runoff generated from a minimum of 5 mm depth of rainfall from all site surfaces through infiltration, evapotranspiration, water harvesting and reuse.1,2,3,4

Tier 2

WQ 2.2 Advanced Stormwater Retention and Reuse (Core)

Retain runoff generated from a minimum of 10 mm depth of rainfall from all site surfaces through infiltration, evapotranspiration, water harvesting and reuse.2,3,4

Tier 3

WQ 2.3 Stormwater Retention and Reuse (Core)

Retain runoff generated from a minimum of 25 mm depth of rainfall from all site surfaces through infiltration, evapotranspiration, water harvesting and reuse.2,3,4,5

Specifications and Resources

  1. Refer to the Wet Weather Flow Management Guidelines for additional detail.
  2. Prioritize the use of green infrastructure and low-impact development practices including: tree and shrub plantings, green roofs and other landscaping to increase evapotranspiration from the site and to increase the amount of permeable surfacing on-site. Refer to the Green Streets Technical Guidelines for more details on at-grade green infrastructure design options.
  3. For water harvesting and reuse, applicants must demonstrate that the water demand would be equal or greater than the rainfall over the site; and ensure proper facilities to balance out any fluctuations in the rainfall and usage as much as possible. Acceptable uses may include but are not limited to: toilet flushing and landscape subsurface irrigation.
  4. Cash-in-lieu of Water Balance will not be permitted.

Tier 1

WQ 3.1 Total Suspended Solids (TSS)

Remove 80 per cent of total suspended solids (TSS) on an annual loading basis from all runoff leaving the site based on the post-development level of imperviousness.1

WQ 3.2 E.Coli Reduction

Control the amount of E. Coli directly entering Lake Ontario and waterfront areas as identified in the Wet Weather Flow Management Guidelines.2

Specifications and Resources

  1. Refer to the Wet Weather Flow Management Guidelines for additional detail.
  2. Refer to the Water Quality Targets for E.coli in the Wet Weather Flow Management Guidelines.

Tier 1

WQ 4.1 Drought-Tolerant Landscapes

Where potable water is used for irrigation, provide drought-tolerant plants for at least 50 per cent of the landscaped site area (including at-grade landscapes, vegetated roofs and walls).1,2

Tier 2

WQ 4.2 Water Efficient Fixtures (Core)

Install water fixtures that achieve at least a 40 per cent reduction in potable water consumption for the building (not including irrigation) over the baseline water fixtures.3,5

WQ 4.3 Efficient Irrigation (Core)

Where soft landscaping exists on the site, reduce potable water use for irrigation by 60 per cent. 4,5

Tier 3

WQ 4.4 Water Efficient Fixtures (Core)

Install water fixtures or use non-potable water sources to achieve at least a 50 per cent reduction in potable water consumption for the building (not including irrigation) over the baseline water fixtures.3,5

Specifications and Resources

  1. Drought-tolerant landscapes and species are provided in accordance with the following City of Toronto guideline document, Drought Tolerant Landscaping: A Resource for Development. This requirement does not apply when non-potable water is used for irrigation.
  2. In choosing tree species, preference should always be given to those native to the area. Where it can be clearly demonstrated that the planting of native tree species would not be appropriate due to site constraints often encountered in urban settings, Urban Forestry may accept non-native, non-invasive species better suited to the particular site.
  3. Refer to LEED® V4 BD+C: WE Credit indoor water use reduction, for further details on how to achieve this requirement. Calculations will be based on estimated occupant usage and baseline fixtures including toilets, urinals, faucets, shower heads. Baseline fixtures include the following: toilets (6.0L), urinals (3.8L) residential faucets (8.3 LPM at 414 kPa), commercial lavatory (restroom) faucets (1.9 LPM at 414 kPa), shower heads (9.5LPM at 550 kPa).
  4. Refer to LEED® V4 BD+C: WE Credit: Outdoor Water Use Reduction Option 2 for further details on how to achieve this requirement. Reductions in potable water must be calculated from a midsummer baseline case. Methods to reduce potable water use for irrigation include high-efficiency irrigation and use of captured rainwater and use of greywater.
  5. Non-potable water sources include greywater or rainwater. Greywater may be used for subsurface irrigation if treated as per the requirements of the Ontario Building Code and CAN/CSA-B12.