Phew. This was my first question. 

"(Old bowling greens are often doused with a range of toxic chemicals, but soil tests were run before anything was planted and came back completely clear, Barnes says)."

Out of old bowling green, hundreds of kilos of fresh food, thanks to volunteers | Stuff.co.nz
https://www.stuff.co.nz/life-style/homed/garden/133015868/out-of-old-bowling-green-hundreds-of-kilos-of-fresh-food-thanks-to-volunteers 

 @3660532c 

Huh that is unusual. 

When a local bowling green was built over the soil was removed to a depth of several meters and replaced with clean fill!

Down at the Chateu the old bowling green there has slowly been replaced with quite a diverse mix of local grasses and mosses.