Whenever in any district reorganized under the provisions of this chapter, extensions or additions are made to the system of improvements of the district to provide drainage or protection from overflow for lands previously found benefited and assessed for the construction of the original system of improvement which are not receiving benefits therefrom in proportion to the benefits found and the assessments levied against such lands, the costs of such extensions or additions shall be included as a cost of maintenance of the improvements of the district and shall be levied and collected in the manner provided for the levy and collection of such costs.