Cal. Water Code § 75781

The failure of any person interested in the district, other than the holders of bonds thereof outstanding at the time of the filing of the petition for exclusion of lands, to show cause, in writing, why the tract or tracts of land mentioned in the petition should not be excluded from the district shall be deemed and taken as an assent by him to the exclusion of such tract or tracts of land, or any part thereof, from the district; and the filing of such petition shall be deemed and taken as an assent by each petitioner to the exclusion from the district of the lands mentioned in the petition, or any part thereof.