As regular followers of this blog may recall, we did some soil tests last year that revealed elevated levels of lead and zinc in our backyard. The cause? Most likely, paint from our 92 year old house and nearly a hundred years of auto exhaust and dust from brake linings.
Applying a little alchemy to turn lead to gold, I think the most productive thing I can do is to help get the word out about lead soil and how common this problem is in urban areas. Towards that end I though I would share five things that we learned from our backyard lead crisis:
- Buyer Beware. When you are shopping for a house do multiple soil tests. Once you buy the house it’s too late. Real estate contracts in California (and I suspect elsewhere) have been loaded up with disclaimers about lead and old houses. I’m no legal expert, but I suspect it would be difficult to go after the seller given the lead clauses we signed in our ignorance.
- The dirt on soil labs. Choose a soil lab that gives detailed results and is willing to do some phone consultation. We used to recommend the cheap tests form UMass, but their results were significantly different than Timberleaf Soil Testing and Wallace Labs, which were more in line with each other. Both Wallace and Timberleaf give you more detailed reports and are both willing to chat on the phone. They cost more but are worth it.
- Raised beds. Not much else to say other than those two words if you want to grow vegetables and have a lead problem. Right now I have a big compost pile going that I made with hay, straw and horse manure. I’ll use this compost along with imported soil to fill the raised beds that I’m going to build this winter. And you can bet that I’m going to test that imported soil first.
- Philosophical lesson. The future health of the human species requires us to be a lot more conservative in the use of chemicals. Lead was known to be a problem since the Romans, but we went ahead and used it anyways in paint and in gasoline and the results have been tragic. Nassim Taleb has written eloquently about the need to approach complex systems like nature and the economy with an attitude of humility and admit our ignorance. When we fool around with complex systems we’re asking for trouble.
- Rhetorical lesson. There should be a logical fallacy called the “appeal to technology.” It’s the idea that there just has to be a technological solution to every problem. This is a very common fallacy in our age. Some people have suggested that I try phytoremediation, the process of growing plants like sunflowers that accumulate lead. At the end of their growing cycle you pull the sunflowers and send them to a toxic waste dump. Sadly, this is just not practical in a residential yard. I would have to pull every living thing, including a mature avocado tree, and grow nothing but sunflowers for the next 20 years. Others have suggested mushrooms as a remediation technique, but they don’t grow well in this dry climate. Lead is an element and it simply doesn’t go away. Once it’s in the ground it’s in the ground. The best way to deal with it is not to use it in the first place. The city of Oakland is trying a more practical solution to deal with lead: applying fish bone meal to lead contaminated soil. Fish bones contain phosphates which bind up lead and make it less bioavailable to plants. Our soil tests indicate that we already have lots of phosphates in our soil, so I’m not sure if adding more would help.
Of all of these points I think the first is the most important. I’ll repeat it again, if you are shopping for property get a soil test.