This problem of contamination of urban soils is a difficult problem -- and people can get downright stubborn about it. I attended the second public meeting of the Mayor's Working Group on Urban Agriculture in March, facilitated by planner John "Tad" Read from the Boston Redevelopment Authority. He had brought someone to speak from the Public Health Commission, Robert Plant, I believe, who is advocating geotextile soil barriers and testing of all produce before sale. In talking over with him the logistics of the geotextile barriers after the meeting, he is envisioning that the barriers will need to be inspected every year -- he sees this as a "natural" part of the process, since soil is turned over every year.
In my view, this is completely unworkable as a procedure. First, not all systems of agriculture turn over the soil, for example, no-till and permaculture systems. Second, if you plant perennial crops, such as asparagus or fruit bushes, you cannot disturb the roots or you will lose the plants. Robert sees no problem with this -- he'll just restrict the plants that can be used. This will impact not just perennials, but those annual crops whose roots grow too deep and would attempt to penetrate the geotextile barrier into the untreated soil. This raises the third objection: under this scheme, the public health commission will dictate the kinds of plants that can be grown, whether or not these are commercially feasible. Fourth, the process of digging up the soil without damaging the barrier, removing the soil and storing it, inspecting the barrier, and then returning the soil is prohibitively difficult. Where would you store the soil? A great deal of the site area would need to be dedicated as open space for this purpose with no other productive use. Most of the small farmers are going to use hand-tools -- thus it is a LOT of extra work at the beginning or end of the season to dig up all the soil, move it, and then put it back --plus it seems that the BRA staff is particularly squeamish about the use of power tools, trucks and other machinery anyway due to perceived public outcry in residential neighborhoods so limited types of tools could be used.