Soil standards
Soil quality standards for agriculture may vary between the federal and provincial/state level. Community groups are advised to take a precautionary approach and follow the most stringent standards for each contaminant.

Land use history
Certain land use histories are associated with specific types of soil contamination. For community groups operating on a restricted budget, determining previous land use can help to narrow the range of contaminants in a given plot that must be tested for and therefore reduce soil testing costs. Previous land use history is usually available at the City Hall of any town.

Soil testing
Testing soil for contamination is generally expensive. Soil testing can range from $10 per sample to $850 per sample depending on how comprehensive the test is. Several samples from different areas of the site are needed to make an accurate assessment of the level of contamination. Additionally, testing must be done after remediation to verify that the technique did indeed work. All testing must be preformed by a certified lab as to adhere to agricultural standards. This tends to increase testing costs.

Given that remediating brownfields for the purpose of urban agriculture can be high-priced, we looked into subsidies for such projects. The main financial assistance program in Quebec was developed by the provincial government's Ministry of Environment and is known as Revi-Sols. Its goal is to encourage landowners and developers to remediate contaminated sites that have the potential for economic development, which may or may not be helpful for community gardens. In the US, the Environmental Protection Agency has set aside $850 million over the next five years for remediation projects, under the name Brownfields Federal Partnership Action Agenda. Not-for-profit organizations may apply for this subsidy.

Analytic framework
The eight remediation techniques were evaluated for the purposes of urban agriculture based on several criteria. These included:
  • Accessibility: Is this technique readily available to non-expert individuals and groups? Is it commercially available, or still in the development phase?
  • Cost: Relatively inexpensive techniques are desirable, as community gardens generally don't generate revenue to pay back the costs of remediating. The costs of consulting and soil testing were not included for the comparison, as they are a necessary first step in every situation.
  • Timeframe: Well-established and funded organizations may plan up to ten years into the future, while funding for younger or smaller groups may be insecure. Remediation techniques vary in the speed in which they can bring soil up to agricultural standards. Therefore, it is crucial for organizations to know how much time must be allotted for remediation. The timeframe considered was from the beginning of treatment to the point when the area is ready for planting
  • Effectiveness for urban agriculture: This refers to the ability of the technique to bring the soil up to agricultural standards. Some techniques can do this in every situation, some depend on the nature and extent of contamination, and some are not effective at this time. A scale of 1 - 3 was used: 1 is unconditionally effective, 2 is conditionally effective, and 3 is ineffective.
  • Environmental effects: Remediation techniques will vary in how environmentally sound they are. Some have toxic by-products, others involve placing materials in the soil that are not biodegradable, while still others have no adverse environmental effects. Often, the disposal of contaminated soil is required at a landfill. Specific environmental effects were listed for each technique.

Using this analytic framework, we evaluated the applicability and feasibility of each remediation technique for use by community organizations. Our results are summarized in Tables 1 & 2.

Table 1. Analytic Framework Applied to Physical Remediation Techniques


Table 2. Analytic Framework Applied to Biological Remediation Techniques

Case studies

The Food Project
The Food Project, a community organization based in Lincoln and Boston, Massachusetts, remediated gardens contaminated with lead. The chosen methods of remedition were composting, phytoremediation and raised beds.
Full remediation was done by bringing in enough soil and compost to act as an adequate barrier between the contaminated soil and the garden vegetables. The soil had to be deep enough so that the roots of the vegetables would not reach the contaminated soil. The remediation of two acres of land cost $26,600 US ($42,000 CAD). Setting up this form of remediation required only a few days work. Gardeners were also encouraged to plant mustard plants and sunflowers. These two plants are known to absorb lead and other metals.
In addition to compost and phytoremediation, the Food Project also built two raised beds for gardeners. This proved cheaper than buying compost and soil, and allowed gardeners to continue gardening every season. For a bed measuring 10x10 ft, the frame costs $300 US ($450 CAD) while the soil/compost mix costs $200 US ($300 CAD). It takes about two and a half hours to build a raised bed.

Phoenix Garden
Eco-Initiatives, the client for this research project, undertook soil remediation to establish the Phoenix community garden on land provided by the Unitarian Church of Montreal. Soil analyses revealed high levels of PAHs, lead, zinc, and copper. The chosen method of remediation was geotextiles.
An area 6 x 20 feet was lined with geotextile along the bottom and sides, after excavation. On the bottom of the plot ¾ inches of gravel was laid, with another sheet of geotextile on top. Eighteen inches of new soil was brought in and laid on top of the geotextile to form the garden.
The total cost of the project was $17 197, not including the donations (soil testing and 33 shrubs). The entire process took 3 days to complete. Rather than disposing of the contaminated soil in a landfill, the soil was simply placed in another area of the garden where vegetables were not going to be cultivated. This helped reduce costs.

© 2002 McGill School of Environment
McGill University
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