A use, building or structure lawfully in existence
on the effective date of this chapter which shall be made nonconforming
at the passage of this chapter or any applicable amendment thereto
may be continued except as otherwise provided in this article.
When a nonconforming structure or use is destroyed
or damaged beyond repair by fire or other casualty or an act of God,
the nonconforming structure or use shall thereafter be terminated.
Damage "beyond repair" for purposes of this section shall occur when
the cost of replacement exceeds 50% of the assessed value of the structure
as adjusted by the county's current equalization rate immediately
prior to the damage.