Cal. Gov. Code § 59214.5

Less than all of the original bonds of a district or more than one overlapping districts may be acquired and canceled in a single proceeding when all of the original bonds to be acquired and canceled have been issued pursuant to the Improvement Act of 1911. When less than all of the original bonds of a district or districts are to be acquired and canceled the boundaries of the new district shall encompass all properties described in the original bonds to be acquired and canceled.