N.J. Stat. § 58:5-22
The cost of the construction or acquisition of said water supply shall be borne by the contracting municipalities in proportion to the amount of water contracted to be taken in the contract between each of the municipalities and the commission. The commission may call upon each of the contracting municipalities to pay from time to time an account of said costs such sums as the commission shall estimate to be needed for that purpose, and shall request payments from each of the municipalities in accordance with the contract until the total cost of the acquisition and construction of the water supply has been completed, and each municipality shall make such payments when so requested. Such cost shall include the salaries and expenses of the commission up to the time of the actual completion of the plant and the commencement of the actual supply of water therefrom.
N.J.S. § 58:5-22