singular debris?

[Arnold Zwicky]

barbara need asks when DEBRIS became singular.  i've used
it all my life as a mass noun, hence as singular in its
agreement pattern.  and i don't recall ever having heard/seen
it used as a plural count noun; LOTS OF DEBRIS WERE SCATTERED
ON THE BEACH makes me break out all over in asterisks, in fact.

arnold (zwicky at csli.stanford.edu, in urbana, illinois,
  for another week)