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:

1. 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.
2. 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.
3. 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.
4. 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.
5. 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.

White sage, yarrow, rosemary and aloe vera–the kind of plants we’ll be planting more of.

Let’s assume that we have a lead problem in our backyard. That’s a big assumption at this point because we now have two very conflicting test results. But, for the sake of an argument, let’s say the first alarming test is true, what are we going to do about it?

• Radical remediation: Remove all the soil in the yard and replace with new soil.
• Cover the contaminated soil so that it doesn’t give off dust, and so people can’t come in direct contact with it, e.g. lay sod, cover the yard with concrete or decking, or lay down a thick layer of mulch.
• Grow ornamental plants only
• Grow all food in raised beds
• Attempt phytoremediation (grow plants that uptake lead, pull them and send them to the dump)
• Move

It turns out we were already doing some of these things, so we’re just going to keep on going as we were with a few changes. Our yard has always been covered in a thick layer of mulch and we do most of our growing in raised beds. We will stop growing edibles directly in the ground. We’d already planned to redesign the yard to include lots more native and Mediterranean flowering plants. These we can’t eat, but will secure the soil and provide food and shelter for lots of beneficial insects who will aid our food crops. We’re really happy that we’ve always mulched, because it has helped keep the (potentially) contaminated soil in place and has increased bio-activity as the mulch decomposes.

This raised be would have to be raised higher.

Regular readers have probably already got this message, but right now we can’t repeat it enough. If there’s a lesson with our backyard lead scare , it’s to practice due diligence when beginning a garden –or better yet, when you buy property–and that means getting a soil test from a soil lab. They’re not that expensive, especially when you consider the high cost of remediation, and the well being of your self and your family.

Test soil for both nutrients and heavy metals when:

• Buying a house or land
• Starting to grow food in your yard  
• Are growing food and have never tested
• Starting a plot in a community garden or a school garden
• Buying soil in bulk

Property does not have to be on the former site of gas station to be suspect. Lead contamination comes not only from lead paint on older houses, but was also deposited all over urban centers and near busy roads via a constant rain of fine particulates from auto emissions.

It really is a shame that lead testing is not a standard part of the inspection phase of home-buying, especially as this is a pervasive problem in urban areas.

Do companies that sell bulk soil test that soil for lead? A few phone calls Darren Butler made to local companies indicate that they don’t. So let the buyer beware here too. Wondering about bagged soils? Susan Carpenter, at the LA Times, tested a bunch and found no problems.  She did find a possible lead link to fish fertilizer, however.

We’ve used all three of these services. UMass is the cheapest by far, but gives the least analysis. However, if you just want your lead level numbers, that’s not a problem.

Wallace Laboratories
UMass Soil Testing Service
Timberleaf Soil Testing

In our next lead post we’ll let you know what our plan is. And we know there’s interest in all this, so over the week we’ll talk about remediation, raised beds, what’s dangerous, what’s edible, and more. Fun for all, guaranteed!