Subjects to the provisions of section 9, where alterations or additions are to be effected, or any part of a building is to be re-elected, the plans to be submitted shall be those mentioned in subsection(1) of section 6:

Provided that-

i) no sewerage plan need be supplied where-

a) the existing sewerage system is not to be affected by or built over by the proposed work; and

b) no new connexions are to be made to the sewerage system;

ii) no plans other than the site-plan and plans and sections of the sewerage work to be undertaken need be provided where the proposed works affect the sewerage system only.