No grant of franchise and no renewal, extension or amendment of such grant shall be valid unless special contract provision is made therein between the city and the grantee or grantees, and which shall inure to the benefit of the patrons of such grantee or grantees, to the effect that for all rate making purposes, whether before the Board of Commissioners of said city or in the courts of the county, the valuation of such utility shall be the physical value of the plant at the time of such inquiry and in no case in excess of its original construction cost, plus the cost of its additions and betterments, and less reasonable depreciation.
(Adopted May 8, 1923)