I suspect they are referring to a pitch pan filled with pitch, a more or less dead level, hot (or possibly cold?) applied asphalt. Fill the pitch pan, then top it off making the top of the pitch slope upward to drain water.
Now there is a novel idea ... topping the pitch pan off, not to mention sloping the top to drain water.
Pitch Pan
http://www.ibroof.com/details/fa_details/fa_15.pdf