(a) Any use, where otherwise legally permitted, listed in section 661.5 of this Part as a use not requiring a permit (NPN) for a particular tidal wetland zone or for an adjacent area, may be undertaken in such tidal wetland zone or adjacent area without a permit under this Part, provided such activity does not involve a regulated activity.

(b) Any alteration of a tidal wetland or adjacent area with respect to which a moratorium permit has been issued pursuant to Part 660 of this Title, or with respect to which a permit pursuant to Part 608 of this Title shall have been issued prior to September 1, 1973, may be undertaken or continued pursuant to the terms of such permit without a permit under this Part; provided, however, that any such alteration that is defined in this Part as a regulated activity, shall be treated for all purposes as a new activity under the provisions of this Part as of August 20, 1977, if such activity has not been substantially commenced as of that date. The department may extend the exemption herein provided for an alteration covered by a moratorium permit or Part 608 permit beyond August 20, 1977, if in the department's judgment the pertinent natural or man-made conditions which existed at and adjacent to the site at the time such permit was issued have not substantially changed and the site is still suitable for the permitted activity. Notwithstanding the foregoing, no alteration of a tidal wetland zone or adjacent area authorized by a permit pursuant to Part 660 or 608 of this Title that is treated as an incompatible use for such zone or area under section 661.5 of this Part shall be undertaken or continued in that zone or area after August 20, 1977, except in compliance with the provisions of this Part.