(1) If it appears to the Board that any group or block of premises may be drained more economically or advantageously in combination than separately, and a Board sewer of sufficient size already exists or is about to be constructed within thirty-five metres of any part of that group or block of premises, the Board may cause that group or block of premises to be drained by a combined operation.
(2) The expenses incurred in carrying out any work under sub-section (1) in respect of any group or block of premises shall be paid by the owners of such premises in such proportion as the Board may determine and shall be recoverable from them as an arrear of charges payable under this Act.
(3) Not less than fifteen days before any such work is commenced, the Board shall give to each such owner,—
(a) written notice of the nature of the proposed work, and
(b) an estimate of the expenses to be incurred in respect thereof and of the proportion of such expenses payable by him.
(4) The Board may require the owners of such group or block of premises to maintain the work executed under this section.