Safe for gardens? Giant beams used for garden beds
We just bought a house near Fern Ridge reservoir and there are 5 massive garden beds built out of very large beams about 8-12 feet long X 12 X 16 inches. They do not show any of the marks of pressure treated wood and they have plenty of signs of decay but they are dark. The last owners told us they are old beams from a bridge that was built temporarily "ages ago" and it was dismantled. How can I determine if they have been treated with something dangerous for growing food? It would be great if I can reuse them as a retaining wall at the edge of my garden but if I need to toss them I will. I can send photos if you like.
Thanks for your inquiry. Please send photos so we can better respond to your question. Try to capture some details and any marks, stains or stamps that might help clarify whatever processes might have been used to preserve the wood.
Most bridge timbers would be treated. Looking at the age of the timbers, they are very old. The fact the timbers are rotting means the "treatment" is almost gone.
Many chemicals were used to treat wood.
An extensive research was done by Lane County showed research showing railroad ties treated with creasote - some reports showed no effect and some reports shows some effect on plants.
The timbers can be used, to make raised beds or barriers or walls. Then with paint with an exterior latex paint and/or cover with plastic so the wood has NOT contact with the soil or plants.