The contracting and participating municipalities may, by supplemental or further contract, replace, enlarge or otherwise increase the capacity of any improvement or works authorized by section 40:63-70 of this title, contracted for or completed, and build and equip all such supplementary sewers, disposal and purification plants and other works and apparatus, as shall be deemed necessary or proper by such municipalities.

All plans and specifications for the construction of such additions, enlargements, or other works, shall be submitted to and approved by the state department of health before the construction thereof is begun; and no works, devices or plants for the disposal, purification or other treatment of the sewage of such municipalities shall be located or constructed in any municipality, without the consent of its governing body.

Such contracts shall provide for the payment of the cost of the construction and maintenance of such additions, enlargements or other works so contracted for, the proportion of the cost to be paid by each of the contracting municipalities, and the manner of the payment of the same. The execution of any such contract shall be first duly authorized by ordinance or resolution of the governing bodies or boards of each of the municipalities charged by law with the duty of constructing sewers and drains in the same.