Assessing Urban Impacted Soil for Urban Gardening: Decision Support Tool Technical Report and Rationale

"Urban gardening is gaining momentum in North America. Urban gardening can provide broad health, environmental, social and economic benefits. The City of Toronto recognizes that urban gardening plays an important role in making Toronto a healthier city. In 2007, City Council directed City staff to promote local food production and remove barriers to urban gardening (City Council Climate Change Action Plan, 2007), and in 2009, City Council adopted a recommendation to support strategies and initiatives that will achieve the overall goal of expanding opportunities for local food production and other urban agricultural activities in the City of Toronto (TEO, 2009).

Often the land available for increasing the urban land base for community gardening are lands that are vacant, abandoned, or previously used for purposes other than food production. As urban gardening expands in Toronto there will be a growing interest to garden on these lands. Previous and current activities on or next to these sites might have resulted in contamination of the soil.

Toronto Public Health (TPH) in collaboration with Parks, Forestry and Recreation (PF&R) and in consultation with the Toronto Environment Office (TEO) developed an urban gardening soil assessment guide to assist City staff in the assessment of potential sites for community and allotment gardens. The guide is a decision-support tool used to identify areas that may be contaminated but could be suitable for food production and to identify appropriate exposure reduction actions based on the condition of the site.

This report begins with a summary of the policy context and drivers supporting urban gardening in the City of Toronto. It outlines some of the potential challenges posed by gardening on urban impacted soils and the need for a decision support tool to guide the assessment, interpretation, selection and risk management for urban gardens. The report summarizes the purpose, scope, objectives and expected outcomes of the initiative. The report provides a step-by-step summary of the guide and a description of a pilot study that was conducted in 2009 to assess the feasibility of the soil sampling guidance. The report then discusses the expected outcomes of the application of the guide and the proposed next steps. Appendix A provides details on the process to develop the guide. Appendix B summarizes the review of the existing decision support tools and soil standards, guidelines and screening values to assess soil safety. Appendix C provides a summary of the evidence informing each step of the guide and Appendix D describes the derivation of Soil Screening Values for urban gardening. Appendix E summarizes a semi-quantitative case-example of the potential health benefits of implementation of this guide. "

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Dakota McGovern