The Public Utilities Commission, upon application, shall determine and allocate the cost of fluoridation among the customers of a public water system and shall from time to time review that determination and allocation as required. In the event that a community water district which has approved fluoridation votes to discontinue fluoridation, the public water system may amortize the remaining cost of its investment in these facilities and allocate the cost of that amortization among its customers, over such period of time as is approved by the Public Utilities Commission.   [PL 1983, c. 463, §4 (NEW).]