How Safe Is Your Soil?
Urban farming has become hugely popular in the East Bay, but lead and other heavy metals in the soil pose potential health risks. Meanwhile, there’s little consensus on what to do about it.
By Nate Seltenrich
East Bay Express
Aug 3, 2011
These are the dilemmas that cities and urban gardeners now face. Yet organizations like City Slicker Farms are working hard to develop safe, practical solutions to soil contamination. Since 2005 the organization has set up 170 backyard gardens, including about 140 in West Oakland, all at no cost to the recipients. The initial step is always a soil test. While few lots exhibit truly dangerous levels, most are elevated and require some form of remediation — typically, covering the soil with mulch and growing vegetables in raised beds.
“So many backyards have lead paint in it, because lead paint was prevalent everywhere,” said executive director Barbara Finnin. “So we’re figuring out instead of digging out all the soil, how can we do that safely here?” In a two-foot-tall raised bed over an impenetrable root barrier, the risk of plant contamination is virtually eliminated, she said. Mulch as thick as six inches elsewhere in the yard helps protect children and animals from direct soil contact.
It’s a simple solution supported by urban farming celebrity Novella Carpenter, who runs Ghost Town Farms on a vacant lot in West Oakland. In her backyard, which is adjacent to a gas station, she tested and found high levels of lead. So she topped the soil with landscape fabric and mulch to protect her animals, which can bio-accumulate lead just like humans and pass them along through their meat, milk, and eggs. Yet she won’t grow any produce there. The majority of her front-yard beds are built directly atop a concrete patio that’s covered with a few inches of dirt. “It’s actually a nice thing to build on concrete,” she said — the danger of contamination is always nil.