No person to whom a permit has been granted under the provisions of Section 62.105 to 62.116, inclusive, shall perform any of the work mentioned in Section 62.105 in an amount or quantity greater than that specified in the permit, except that upon approval by the City Engineer, additional work may be done under the provisions of this permit in an amount not greater than ten per cent (10%) of the amount specified in the permit. Any bond posted in connection with the original permit shall be deemed to cover any such additional work as may be approved pursuant to this section, within the limit mentioned herein.