If any project, whether original, modified, substituted or other, already adopted under this part, remains uncompleted, whether in whole or in part, and any assessment levied under Part 9 (commencing with Section 46000) of this division on the basis of the project remains uncalled, either in whole or in part, and if the board finds, through resolution adopted by a two-thirds vote of its entire membership, that, for reasons explicitly stated in the resolution, the project should be materially modified or should be completely abandoned and another project be substituted in its place, then the board shall proceed under Chapter 1 (commencing with Section 42200) of this part to prepare a new report which shall be complete in itself and which shall set up the existing project as materially modified or a new project to be substituted in its place.