I want to create a vegetable garden in my garden, but I have a privacy fence that is treated with copper, chrome and arsenic (CCA). How far should I plant from the fence to avoid CCA contaminants that may have leached from the fence into the ground?
CCA treated wood, often referred to as pressure treated wood, is very common and you are right to be concerned that it will affect your garden. The three main chemicals that can get into your soil – copper, chromium, and arsenic – are likely concentrated just inches from the base of your fence. Studies analyzing the chemical content of the soil in raised beds with CCA-treated wood found high concentrations of arsenic in the soil within 2 inches of the wood and normal arsenic concentrations within 2 feet of the wood. Because wooden fences have more surface area for chemicals to leach from and shade from, I recommend being careful and allowing a 3 foot buffer between your fence and your vegetables. That way, they should be protected from contamination and excessive shade.
In 2003, consumer pressure finally forced the wood industry to switch to less toxic, arsenic-free treatment alternatives.
– Barbara Pleasant, contributing editor