(a) For the purposes of this section, the term “threshold limit” shall apply to any structure or addition thereto (1) having four stories, (2) sixty feet in height, (3) with a clear span of one hundred fifty feet in width, (4) containing one hundred fifty thousand square feet of total gross floor area, or (5) with an occupancy of one thousand persons.
(b) The following use groups shall have the following additional threshold limits: