On Tue, 25 Jun 2013 17:35:22 -0500, The Daring Dufas wrote:

I wonder if it could have been damage done by a drain bamaged individual
wielding a wild weed eater or a lawless lawnmower?

Most likely, it was some big fat guy who was composting
kitchen scraps with pick and shovel and rake ... who didn't
realize what was buried under the soil prior to his arrival.