"External floating roof" means the cover of an open-top storage tank, which consists of a double deck or pontoon single deck that rests upon and is supported by the VOL being contained, and that is equipped with a closure seal to close the space between the roof edge and tank shell.

Source. (See Revision Note at chapter heading for Env-A 1200) #9933, eff 6-1-11; ss by #12899, eff 10-17-19