If the board of viewers deems it advisable it may, prior to the issuance of refunding bonds, order the cancellation of the assessments levied for the payment of the bonds refunded, except in so far as such assessments were levied for the payment of bonds not actually retired by the issuance of refunding bonds, and may direct the preparation of new assessment rolls and the levy and collection of new assessments sufficient for the payment of principal of and interest on such refunding bonds.