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.
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
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
The eight remediation
techniques were evaluated for the purposes of urban agriculture based
on several criteria. These included:
Is this technique readily available to non-expert individuals and
groups? Is it commercially available, or still in the development
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.
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
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.
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.
1. Analytic Framework Applied to Physical Remediation Techniques
2. Analytic Framework Applied to Biological Remediation Techniques
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.
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.
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
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
3534 University, Montreal, Quebec, Canada H3A 2A7