Land Reuse for Urban Agriculture

Hava Blair – Minnesota Brownfields, Program Coordinator:

My first job after college was transforming a golf course into an urban farm. I graduated with a degree in geology and a passion for food and community service, and I jumped at the opportunity to participate in the growing urban agriculture movement. Although the term “brownfield” was not in my vocabulary back then, I recognize now that our work to develop the urban farm at Riverview Gardens in Appleton, Wisconsin touched on several key considerations that apply broadly to reusing urban land to grow food.

Understand Historical Use  
As with other brownfield sites, knowledge of historical activities at your site can help identify potential contamination risks. In the case of our golf course, this meant understanding the types and locations of pesticide, fungicide, and fertilizer applications that were used during the 100+ years that the site was a private golf course. Possible soil contaminants will vary depending on the previous uses of the land.

Aerial view of the Riverview Gardens – Appleton, WI.

You can start learning more about environmental investigations and clean-ups in your community by searching the Minnesota Pollution Control Agency’s (MPCA) “What’s in My Neighborhood” (WIMN) mapping tool. This resource contains a wealth of information about potentially contaminated sites, clean-ups, environmental permits, and registrations issued by the MPCA. The Minnesota Department of Agriculture (MDA) has a WIMN mapping tool with information agricultural chemical spills and clean-ups throughout the state.

Identify Possible Contaminants
Some common and widespread soil contaminants in the urban environment include lead, arsenic, cadmium, and poly-aromatic hydrocarbons (PAHs).  These contaminants can be found throughout many urban areas on residential, commercial, and industrial sites.  Depending on the previous use of a given site, other contaminants may be present. Some examples of previous uses that involve potential contaminants include: gas stations, dry cleaners, metal finishing operations, and body shops. These uses and others are red flags that require caution and further investigation before a site is used for food production.

Test the Soil
For home gardeners, the Minnesota Institute of Sustainable Agriculture and University of Minnesota Extension have developed a helpful fact sheet that outlines more information about common urban soil contaminants, soil testing, and ways to minimize potential exposure if contaminants are a concern.  Eligible non-profits and local government units in Hennepin County may apply for grant assistance to test the soil in community gardens – see our Brownfield Gap Financing page for more information. For prospective urban farm businesses like the urban farm I was involved with, it may make sense to hire an environmental consultant to assess the potential risks of reusing an urban site to grow food. At Riverview Gardens, we identified the former tees and greens as areas that were at risk of heavy metal build-up from historical pesticide/fungicide use.

Consider Innovative Growing Techniques
Urban agriculture takes many forms, from small backyard gardens to intensive commercial production. Back at Riverview Gardens, we had the luxury of a large 72-acre site across the Fox River from downtown Appleton, WI to develop into vegetable gardens, orchards, and community park space. However, large open sites suitable for farming are not the norm in a fully developed urban area. Urban agriculture offers some exciting opportunities to utilize technology and existing infrastructure to grow food with a fraction of the space, water, energy, and fertilizer used in conventional farming systems.

In some cases, urban farming may involve the adaptive reuse of existing structures for indoor food production using innovative techniques such as aquaculture, hydroponics, or aeroponics. Urban Organics in St. Paul is a great example of an urban agriculture business that leverages the existing infrastructure from historic breweries on both of their sites for access to water for aquaculture systems, thus using a tiny fraction of the water used in traditional farming systems.

Recognize Gaps in Science and Policy
The land clean-up standards used today were developed to protect people from exposure to unsafe levels of contaminants during the activities associated with living or working on a site, but these do not account for specific farming activities or the risk of consuming food grown on the site. Currently, there are no definitive standards for urban soil contaminant levels that are safe for food production. The U.S. Environmental Protection Agency (EPA) advises the use of residential clean-up values as a benchmark for safe urban food production until research can provide a more definitive standard specifically for agricultural reuse on potentially contaminated sites.

Hava pictured with cabbage grown at Riverview Gardens.

Some complicating factors that impact exposure and health risk assessment for urban agriculture include many site-specific considerations: soil quality, soil chemistry, cultivation practices, plant uptake and bioavailability, and more. The U.S. EPA explains that despite these complicating factors, research has found that the predominant exposure routes of concern are direct contact with or ingestion of potentially contaminated soils. Knowing this information, it is possible to implement best management practices (BMPs) like raised beds, mulch, and building soil organic matter that can reduce risk of exposure to contaminants.

Learn More and Grow
The U.S. EPA’s “Brownfields and Urban Agriculture: Interim Guidelines for Safe Gardening Practices” provides a more detailed process for identifying and investigating potential risks at a site intended for agricultural reuse, and recommends common-sense best practices that all gardeners can use to minimize risk. Many additional resources are available about urban agriculture – a few are listed below.