A regulated activity that was approved prior to the passage of this chapter and to which significant economic resources have been committed pursuant to such approval but which does not conform to this chapter may be continued subject to the following:
A. No such activity shall be expanded, changed, enlarged, or altered in any way that increases the extent of its nonconformity without a permit issued pursuant to the provisions of this chapter.
B. Except for cases of discontinuance as part of a normal agricultural activity, if a nonconforming activity is discontinued for twelve consecutive months, any resumption of the activity shall conform to this chapter.
C. If a nonconforming use or activity is destroyed by human activities or an act of God, it shall not be resumed except in conformity with the provisions of this chapter.
D. Activities or adjuncts thereof that are or become nuisances shall not be entitled to continue as nonconforming activities.