(1)Any person liable to the payment of a betterment fee may, at his option, instead of making a payment thereof to the Board, execute an agreement with the Board to leave the said payment outstanding as a charge on his interest in the land, subject to the payment in perpetuity of interest at the rate of [ten per centum per annum] [Words substituted for the words 'six per centum per annum' by W.B. Act 43 of 1983.], the first annual payment of such interest to be made one year from the date referred to in section 85.
