Any lawful nonconforming use which existed at the time of adoption of this chapter may be continued and any existing structures designed, arranged, intended or devoted to a nonconforming use may be structurally altered subject to the following regulations:

In the event that there is a cessation of operation of any nonconforming use for a period of 12 consecutive calendar months, the same shall be prima facie evidence of an abandonment of the use. Any subsequent exercise of such abandoned nonconforming use shall be deemed a violation of the terms of this chapter.

Any nonconforming building which has been destroyed or damaged by fire, explosion, act of God or by a public enemy to the extent of 70% or more of its assessed valuation shall thereafter conform to the provisions of this chapter. Where more than 30% of the assessed value of the building remains after such damage, such structure may be restored to the same nonconforming use as existed before such damage.

Any existing principal structure on a residential lot which is nonconforming as to one or more bulk standards of the Zoning Ordinance may be expanded, enlarged or altered, provided that any existing nonconformity is not further violated and that no new nonconforming conditions are created.

Nothing in this chapter shall require any change in plans, construction or designated use of a structure for which a building permit has been issued when construction has been diligently prosecuted within six months following the date of such permit, and completed within the term of such permit.

Any nonconforming use or structure existing at the time of adoption of this chapter may be continued upon the lot or in the building so occupied and any structure may be restored or repaired in the event of partial destruction thereof.

Nothing in this chapter shall be interpreted as implied authorization for or approval of the continuance of the use of a structure or premises in violation of zoning regulations in effect at the time of adoption of this chapter.

The foregoing provisions of this section shall also apply to structures, land or uses which hereafter become nonconforming due to any reclassification of zones under this chapter or any subsequent change in the regulations of this chapter.

Land, buildings and appurtenances thereto shall be held as nonconforming and subject to all provisions regarding nonconforming use upon completion of actions authorized by a variance of exception to the zoning regulations or the meeting of conditions required.