Performance measures for stormwater management, green infrastructure and potable water reduction.Toronto Green Standard Water Quality Icon


WQ 1.1 Water Balance, Quality & Quantity Control

Design the site to achieve all Water Balance, Water Quality and Water Quantity control targets required by the Wet Weather Flow Management Guidelines: 1,2,3

  1. Water Balance- Retain a minimum of 50% of the total average annual rainfall volume (or equivalent 5 mm from each rainfall event) generated from all site surfaces through infiltration, evapotranspiration, water harvesting and/or reuse, in accordance with the Wet Weather Flow Management Guidelines.
  2. Water Quality- Provide an enhanced level of protection for water quality through the long-term average removal of 80% of Total Suspended Solids (TSS) on an annual loading basis from all runoff leaving the site, in accordance with the Wet Weather Flow Management Guidelines. Provide E.coli control for direct discharges to Lake Ontario or for discharges generated from waterfront sites, where deemed necessary and in accordance with the Wet Weather Flow Management Guidelines.
  3. Water Quantity- Provide peak flow control following applicable Wet Weather Flow Management Guideline requirements for flood flow management, erosion control and discharge to municipal sewers.

WQ 1.2 Green Streets

Where new streets are proposed, capture and control stormwater runoff to the maximum extent possible, from all contributing drainage areas using Green Infrastructure in accordance with the City’s green infrastructure standards and specifications for the Right-of-Way. 3,4

WQ 1.3 On-site Green Infrastructure

Ensure that the total landscaped site area, located at and above grade, includes at least one of the following features: 5,6,7,8,9,10

  • A Green Roof covering at least 80% of Available Roof Space;
  • An Intensive Green Roof for 80% of the Green Roof Area provided;
  • Biodiverse green roof to support pollinator species covering a minimum of 50% Green Roof Area;
  • 25% of the Lot Area at or above-grade, planted with native flowering/pollinator species;
  • At-grade Bioretention facilities provided to capture and control 75% of runoff from on-site hardscape surfaces; or
  • Reforestation of a portion of the site (beyond the limit of a stewardship plan).

Specifications and Resources

  1. Refer to the Wet Weather Flow Management Guidelines for additional detail.
  2. Rainwater harvesting and re-use options must be in compliance with the Toronto Municipal Code, Chapter 681 and the Ontario Building Code. Currently, allowable re-use options for harvested rainwater include flushing of water closets/urinals and sub-surface irrigation/infiltration.
  3. Prioritize the use of green infrastructure and vegetated low-impact development practices to increase evapotranspiration and infiltration through pervious surfaces on-site, where feasible. Refer to the Green Streets Technical Guidelines for more details on at-grade green infrastructure design options.
  4. Refer to the City of Toronto Green Infrastructure Standards for design criteria, Construction Specifications and Construction Drawings for Green Infrastructure in the Right-of-Way. For questions on implementation contact GreenStreetsTO.
  5. Refer to the Green Roof By-law for definitions of Green Roof and Available Roof Space, details on calculating the green roof area required and the Toronto Green Roof Construction Standard. Green Roof Area is the total roof area occupied by a Green Roof.
  6. Intensive Green Roofs have deeper substrates that can support a greater variety of plant species. They meet the definition of a Green Roof under the Green Roof By-law, and must include:
    1. A deeper growing medium with a minimum depth of 150 mm; and
    2. A diverse mix of plants appropriate to the growing media depth and roof height. Plants may include sedums, grasses, drought tolerant perennials, and larger plants and trees where appropriate.
  7. Biodiverse Green Roofs are designed to support pollinator species. They include an Intensive Green Roof that is located at or below the 8th storey of the building and follow the recommended plant species found in Appendix A of the Design Guidelines for Biodiverse Green Roofs, with at least two species in bloom at all periods over the growing season. The design must also address two or more applicable Design Strategies from section 4.2 of the Guideline.
  8. To support green roof performance, regular ongoing maintenance is required for Intensive and Biodiverse Green Roofs. Install a permanent irrigation system to provide supplemental watering when necessary; provide direct access to the roof for maintenance through a door or hatch located away from the edge of the roof to enable safe maintenance. A Green Roof maintenance contract with a qualified green roof professional is recommended for at least the first 5 years of the green roof.
  9. Native plants provide pollen and nectar for food, as well as places to nest and overwinter for native pollinator species. At-grade planting areas must be designed to meet PollinateTO garden requirements, and include the following:
    1. 75 per cent of plants must be native perennial species;
    2. at least twelve perennial plants, one type of native goldenrod and two different types of larval host plants including milkweed;
    3. plants providing continuous bloom with a minimum of 2 species in bloom in the spring, summer and fall; and
    4. nesting and overwintering sites – such as dead wood, hollow and pithy stems, access to bare sandy soil, fallen leaves.

    For suggestions on species selection, refer to the City of Toronto native wildflower, trees and shrubs lists. Above-grade planting areas must meet the requirements for a Biodiverse Green Roof to support pollinator species. Lot Area is the horizontal area within all the lot lines of a lot. Refer to City of Toronto Zoning By-law 569-2013.

  10. Bioretention facilities are structural stormwater controls effective at improving stormwater runoff quality and reducing total stormwater runoff using a combination of soil filter media and vegetation to filter, treat, temporarily retain, and infiltrate stormwater runoff. Examples include: Bioretention planters, bioretention curb extensions/bump-outs, bioretention cells and rain gardens.


WQ 2.1 Water-Efficient Fixtures

Install water fixtures or use non-potable water sources that achieve at least a 40% reduction in potable water consumption for the building (not including irrigation) over the baseline water fixtures. 1

WQ 2.2 Efficient Irrigation

Where soft landscaping exists on the site, reduce potable water use for irrigation by 60%. 2

Specifications and Resources
  1. Refer to LEED® V4.1 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).
  2.  Refer to LEED® V4.1 BD+C: WE Credit Outdoor Water Use Reduction.