In Etowah County, the chair and board members of the Gadsden Water Works and Sewer Board are hereby entitled to expense allowances to be paid as follows: The chair of the board shall receive one hundred fifty dollars ($150) per month; the members of the board shall receive a per diem allowance of twenty-five dollars ($25) for each day on which the board meets. The expense allowances provided herein shall be in lieu of all other compensation or expense allowance heretofore provided by law.