...But where does it go?

Okay, I need help with some meditation-visualizations here. I've been taking an awesome yoga class for the past several months, and when we end in the final corpse pose, the instructor always talks about letting go of whatever stress we've pulled loose, letting it fall away, letting it sink down into the floor.

I love that idea, but I can't help imagining the space about six feet below the floor as a dark seething cesspool of accumulated stress dumped by class after class, week after week, of yoga practitioners. It's a little unsettling. So lately I've been trying to visualize the space beneath the floor as a river, carrying all that stress away and washing us clean. But then I can't help wondering where the river goes, and picturing a big karmic dead zone like where the Mississippi dumps all its nasty fertilizer and chemical load into the Gulf of Mexico, killing everything off.

I'm so attuned to environmental issues that I keep thinking of stress like toxic psychological waste: sure, I can get rid of it and that's nice for me, but where does it end up??