World's Largest Floating Solar Plant built over former Coal Mine

The world’s largest floating solar power plant is now online in China. The 40MW plant is now afloat in water four to 10 meters deep, and successfully linked to China’s grid. The placement was chosen in large part because the area was previously the location of coal mining operations; and, as a result, the water there is now mineralized and mostly useless. The lake itself was only formed after years of mining operations, the surrounding land collapsed and created a cavity that was filled with rainwater.

https://futurism.com/the-worlds-largest-floating-solar-plant-is-finally-online/