I made a mistake and installed a retaining wall in my garden made out of creosote-treated wood from an old bridge, which contains chromium copper arsenate. Our strawberries planted below the wall shortly began to wilt, and our raspberries followed suit the following year. I was concerned about arsenic toxicity, so I got a soil test — fortunately, arsenic levels are fine, but copper is about 40x higher than it should be (24ppm).
My main question is, how can I remove the copper from my soil? Is there something I can plant that will extract the copper? I know there is something similar for arsenic, and I also know grasses do better than woody plants in copper. This page explains that ensuring ample zinc can help, and my soil test suggested adding nitrogen via blood meal would help reduce copper bioavailability, but I'd rather not spend lots of time and money amending, when I can find a more permanent fix.
Secondarily, should I remove the wall? I was hoping I could maybe install a French drain below it to avoid runoff from getting into the garden soil below it.
Below are screenshots of my soil test.
