(1) Every retaining-wall which does not comply with the provisions of section 46 or 46 shall be designed in accordance with the requirements of section 63 to 82.

(2) A French drain or other efficient form of drain shall be provided behind a wall over 400 millimetres in height, intended to act as a retaining -wall, to drain fill, and steps shall be taken, where needed, to prevent erosion of the fill near the drain.

(3) weep-holes to carry off water from such drain shall be provided through such a wall, of size and spacings suitable in the opinion of the local authority, for the soil conditions prevailing.

(4) A surface-drain shall be provided in front of the retaining-wall to dispose of water from the weep-holes.

(5) Notwithstanding the provisions of subsections (2) to (4), the local authority may approve other similarly adequate means to drain the fill behind the retaining-wall, and to dispose the water so drained off.