I noticed that when I do laundry in the basement, (machine drains to
basement sink), the sink backs up and drains veeeery slowly. There's
no lint in the sink pipe. So I looked around, and found that both of
my basement floor drains (the large holes in the floor) are full of
SOIL and some LEAVES (mostly soil), nearly to the floor level. The
soil seems densely packed (I spooned some out), which means I can't
DIY the problem by a hand snake.

I wonder: is it something doable by drain specialists with a motorized
snake? Or too serious and requires heavy machinery (knock on wood)?
What might have caused the drains to fill with all this debris?

Thanks for all your tips!