(a) The Assistant Secretary may partially approve a plan under part 1902 of this chapter whenever:
(1) The portion to be approved meets the requirements of part 1902;
(2) The plan covers more than one occupational safety and health issue; and
(3) Portions of the plan to be approved are reasonably separable from the remainder of the plan.
(b) Whenever the Assistant Secretary approves only a portion of a State plan, he may give notice to the State of an opportunity to show cause why a proceeding should not be commenced for disapproval of the remainder of the plan under subpart C of part 1902 before commencing such a proceeding.