For anyone else out there that looked at the picture and their first thought was "are those tanks open to the rain?" thinking they were just open cylinders see

For anyone else out there that looked at the picture and their first thought was "are those tanks open to the rain?" thinking they were just open cylinders seems it's called a floating roof tank : https://en.wikipedia.org/wiki/External_floating_roof_tank https://en.wikipedia.org/wiki/External_floating_roof_tank And it prevents vapor loss or needing vapor overhead as the roof floats directly on the surface. Rain/snow water is pumped out off the top of the roof as needed.