Municipality: Toronto and Region Conservation Authority (TRCA) Implementation: 2012-06-21
Policy Name: Preserving and Restoring Healthy Soil Contact: Dean Young
Department: Watershed Management Title: Project Manager, Sustainable Tech
Focus:
Community profile:

The Greater Toronto Area is the largest metropolitan area in Canada – home to six million people and counting with a   population expected to grow to nine million by 2036. It spans an area of 7,125 square kilometres and includes the City of Toronto and surrounding regional municipalities of Durham, Halton, Peel and York. 

The Toronto and Region Conservation Authority (TRCA) jurisdiction is 2,506 square kilometres and includes the City of Toronto, parts of the Regions of Durham, Peel and York and a small portion of the Township of Adjala-Tosorontio and   Town of Mono. It includes nine river systems – from the Etobicoke Creek in the west and Carruthers Creek in the east, and approximately 60 kilometres of the Lake Ontario waterfront.

Short Description:

Guidance document describing recommended best practices and minimum standards for preserving and restoring healthy soil in landscaped areas during urban construction for stormwater management, water conservation and urban tree health benefits.

Background:

The way in which landscaped portions of urban environments are constructed and managed affects how absorbent they are to stormwater, in addition to the level of effort that will be required to re-establish and maintain healthy vegetation and the lifespan of the plantings. If best practices to preserve or restore healthy functioning soils in these areas are not applied during construction, changes to soil structure, biology and organic matter content and the effects of compaction can cause them to function more like impervious surfaces. This makes the standard practice of directing roof drainage to them (i.e., roof downspout disconnection) less effective than it could be at reducing urban runoff and contaminant loads to receiving waters. Furthermore, poorer quality planting environments are produced that require more irrigation, fertilizer and effort to re-establish and maintain vegetation and urban tree canopy.

This best practices guide provides both the rationale and practical guidance needed to improve conventional urban construction soil management practices in Ontario such that landscaped areas that are more absorbent, drought tolerant and healthier growing environments are produced. It is a useful resource to designers and engineers involved in urban and landscape design, government agencies involved in the permitting and inspection of urban construction projects and contractors involved in urban construction and landscaping.

Soil preservation and restoration practices qualify for credits in green building certification systems like LEED and The Sustainable Sites Initiative. Including soil testing requirements and the recommended minimum standards for soil depth and quality in all landscaped areas as part of municipal design standards would help them achieve environmental objectives related to stormwater management, water conservation and urban tree health.

Step by Step Process:

  • Recommendations for minimum soil quality standards in landscaped areas that receive roof drainage were included in the Low Impact Development Stormwater Management Planning and Design Guide (CVC & TRCA, 2010) as a non-structural best management practice but detailed guidance on other soil management best practices was not provided nor how to implement and inspect them on construction sites.
  • Funding to develop more detailed guidance on soil management best practices for urban construction for stormwater management benefits was received by TRCA in 2011 from the Ontario Ministry of the Environment through the Toronto Area Remedial Action Plan, City of Toronto, Regional Municipality of Peel Regional Municipality of York, and the Department of Fisheries and Oceans Canada.
  • TRCA prepared a draft guidance document based on similar guidance provided in several jurisdictions throughout the United States (e.g., Western Washington, Maryland, Minnesota, Pennsylvania, Virginia, New York) and green building certification system guidelines (e.g., The Sustainable Sites Initiative™) with adaptations to suit an Ontario context.
  • TRCA coordinated internal and external reviews of the draft guidance document.  Internal reviewers provided perspectives ranging from development proposal review and approvals, water resource engineers, ecologists, and ecological restoration practitioners.  External reviewers provided perspectives ranging from municipal planning, public works, parks and recreation and urban forestry department representatives, land development engineering consultants and landscaping industry representatives. 
  • Information sharing meetings were hosted by TRCA to answer any questions that internal and external reviewers had about the guidance provided in the document and to solicit feedback on the recommended minimum standards and options for promoting widespread implementation of the best practices.
  • TRCA finalized the guidance document, incorporating revisions suggested by reviewers and posted it to the Sustainable Technologies Evaluation Program website (www.sustainabletechnologies.ca).

Primary Drivers:

The health of urban rivers, lakes and wetlands continues to decline with increasing urbanization, even with implementation of current stormwater management standards. Widespread implementation of the best practices described in this guidance document will help to reduce the volume of runoff leaving individual properties as well as the pollutant load to receiving waters and are suitable in both greenfield and redevelopment/renovation contexts.

Secondary Drivers:

Urban trees provide a multitude of environmental benefits including air quality improvement, shading to reduce the urban heat island effect, habitat for wildlife, aesthetics and interception and evaporation of stormwater. To reap these benefits, urban trees need growing environments that allow them to reach maturity. Widespread implementation of the best practices described in this guidance document will help to improve the drought tolerance and lifespan of urban trees (i.e. urban tree health). They will also help to produce lawns and gardens that require less fertilizer and irrigation to become established (i.e. water conservation).

Enablers:

Funding to develop this guidance document was received by TRCA in 2011 from the Ontario Ministry of the Environment through the Toronto Area Remedial Action Plan, City of Toronto, Regional Municipality of Peel Regional Municipality of York, and the Department of Fisheries and Oceans Canada.

Champions:

The Director of Watershed Management and Director of Ecology at the Toronto and Region Conservation Authority were champions of this initiative. 

Obstacles:

Achieving widespread adoption of these best practices through policy/urban design guidelines will required considerable additional effort to promote them to Ontario municipalities and other conservation authorities which was beyond the scope of the project.

Opportunities:

Promoting these best practices on a voluntary basis by working with land developers and their engineering consultants and landscape construction contractors and evaluating the costs and benefits will provide opportunities to demonstrate their effectiveness and potentially to refine or further develop the guidance document in the future.

Obstacles:

The land development industry questioned the technical feasibility and cost associated with some of the best practices, particularly scarifying subsoils prior to topsoil spreading. 

Opportunities:

The landscaping industry showed interest in training opportunities on the best practices described in the document.

Outcome:

Key informant interviews with water resource engineering consultants suggest that some land developers are willing to double the depth of topsoil typically applied to landscaped areas and to implement improved topsoil stripping and stockpiling practices, soil testing, subsoil scarification and compost amendment on a pilot study basis.

Lessons Learned:

Consultation across internal divisions and with external stakeholders and technical disciplines was critical to the development of this guidance document.

There is a clear interest in training on the best practices in this guidance document so in future initiatives this should anticipated.

Applicability Across Ontario:

The guidance contained in this document is applicable across Ontario (not specific to the Toronto and Region Conservation jurisdiction).

Similar Tools Used by Other Municipalities:

Some Ontario municipalities require soil testing prior to its use in constructing landscaped areas and/or have standard specifications for soil depth and quality for landscaped areas in the public realm. A comprehensive review of where these types of requirements exist was beyond the scope if this project.

Conservation authorities have control over the quality of soil placed within regulated areas.

Further Information:

For more information, please contact Dean Young, Project Manager, Sustainable Technologies, Toronto and Region Conservation. Tele: 289-268-3904; Email: dyoung@trca.on.ca

Sustainable Technologies Evaluation Program (STEP) website on this topic

http://sustainabletechnologies.ca/wp/clean-water/soil-management/preserving-and-restoring-healthy-soil-best-practices-for-urban-construction/ 

Preserving and Restoring Healthy Soil: Best Practices for Urban Construction

http://sustainabletechnologies.ca/wp/wp-content/uploads/2013/02/TRCA_2012_Preserving-and-Restoring-Healthy-Soil_Full-Report-REDUCED.pdf