Chad on the airstrip

[Douglas G. Wilson]

On the Web, I find

http://www.airnav.com/airport/INS

--  a description of the Indian Springs AF Aux. Airport in Nevada. The
runway has a "smooth packed chad surface"!

Is it an alternative spelling of "chat" = "gravel"? Or an erroneous
spelling thereof? Or a joke (the page is dated 30 Nov. 2000)? Or is the
runway covered with confetti? Or does someone use "chad" = "gravel"
currently in the US?

["Packed chat surface" is found on the Web here and there.]

-- Doug Wilson