Thursday, July 25, 2013

Latest SACG Soil Test

When we received from the City the loan of our second rain tank last August, it also came with a requirement that we submit our soil for free testing by OSU.  However, no one ever contacted me about submitting a soil sample.  New gardener Sabrina then started asking about soil tests in April because of her young son, Zephyr, so I gave her copies of our 2009 results from UMass at Amherst and nudged and pushed until arrangements were made in June for a new test.   After all, I’m sure that some of the dust from the demolition of the eyesore next door probably landed on the Garden (particularly when last year’s June 29 derecho hit us about 30 minutes after the building came down).   While Rebuilding Together and the City attempted to make contact with the right people at OSU to provide the soil test, I discovered from Dr. Darraugh that CLC Labs would tests for lead in our soil (and CLC says their test is better than the UMass test we received in 2009) for $45.  CLC would also test for the EPA Heavy Metals (including arsenic and 9 other heavy metals) for $190.  CLC would not test for organic toxins, like dioxin or petroleum.

Once the City and Rebuilding Together made arrangements with OSU for a free test, however, I dropped off the sample myself at Cottman Hall on June 14.  OSU still hasn't finished our soil testing (for nutrients and pH) and hasn’t give me an ETA on the rest of the test. (In past years, we have tested off the charts for nutrients, slightly alkaline in 2009 and neutral in 2011 when CLC tested our soil). However, wunderkind Kristin Minca did get back to me a few weeks ago with the results of the total soils extraction test (the test used by the Ohio EPA) for contaminants.  I have attached those results for your edification.

Soil Test Results for Stoddart Ave. Community Garden
Total concentration in soil
Ohio background concentration
Ohio EPA
VAP standards
mg kg-1
mg kg-1
mg kg-1


The first column reflects our soil.  The second column is the amount of that element one naturally finds in the soil in rural areas.  You will note that our urban soil has very elevated levels compared to rural soil.    Of course I became concerned by that and this is what I was told:

Your sample had elevated levels for all the metals we tested for, but none of the metals exceed the risk based standards for Ohio. What this tells me is there was activity on the properties that added metals to the soils (possibly from lead paint, or galvanized metal plumbing), which is common for the urban gardens I've tested.

I recommend you continue to use your soil for food production, but be sure to wash all the produce you grow there very thoroughly before consumption to remove any soil residue that could be present.

(emphasis in original).  Still concerned, I pushed for more information and was told:

You should know that the concentrations of your soil are similar to other urban soils. The background concentrations that have been done in Ohio and the US are typically rural agricultural soils and don't reflect the anthropogenic influence of urban cities. But your soil isn't a risk. People should thoroughly wash produce from any place including the grocery because dust can adhere to those products too and pose the same risks.

Still concerned, I pushed again -- as you all know only I can do --  and this morning she gave me the soil contamination standards used by the Ohio EPA.  They are apparently the standards used in the Voluntary Action Program (VAP) to remediate contaminated sites.   Those standards are reflected in the third column above.   Our soil is well below those levels.  So, I breathed a sigh of relief.

Nonetheless, Kristen -- who now also works for the Ohio EPA and knows I'm thinking about the neighborhood kids and Zephyr -- tells me this about the VAP standards reflected in the third column:

Attached are your results with the standards for noncarcinogenic risk for soil ingestion based on a child. Carcinogenic risk is slightly lower for these compounds (mostly As at 6.7 mg/kg but background concentrations suggest this may be unrealistic).

Again, this concerned me a bit.  So, our children are at risk just for walking out the door?  She responds as follows:
Recent soil surveys in Ohio show that the natural background for Arsenic ranges between 5 mg/kg and 30 mg/kg because of the subsurface geology in our state. Most soils I've seen has Arsenic levels around 10 mg/kg. Risk assessment standards are based on the very worst case scenario, a child with hand to mouth tendencies eating soil while fasting. So the exposure for community gardeners wouldn't be the same, especially if they practice good gardening by washing their hands, tools, and especially the produce.
I feel better now, don’t you?

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