Wat. Code, § 55187

All acts and proceedings heretofore or hereafter taken by or on behalf of a county waterworks district for the formation of a district or for the annexation to an existing district and for the authorization, issuance, sale, or exchange of bonds of the district or for the annexed territory may be confirmed, validated, and declared legally effective in the manner provided in this section.

The board may instruct the clerk of the board to mail a notice to all owners of property within the county waterworks district, as their names and addresses appear on the last equalized county assessment roll, or as known to the clerk. Such notice shall include the name of the district, the date the district was ordered formed or the date of the annexation to an existing district, the amount of bonds authorized, and a statement that, commencing with the date of mailing of said notice there shall be a 60-calendar-day period during which period any property owner may file an action contesting the validity of the district’s formation, the annexation to an existing district or the bond authorization. The clerk shall make and file, with the board a certificate of mailing of the notices. The board may order the clerk to include such other additional information that it deems pertinent.

If no action is filed during the 60-day period, the district’s formation or the annexation to an existing district and the bond authorization are valid and uncontestable.