A petition for incorporation must be signed by registered voters resident within the limits of the proposed city or town equal in number to at least ten percent of the number of voters residing within the proposed city or town and filed with the auditor of the county in which all, or the largest portion of, the proposed city or town is located. The petition must be filed with the auditor by no later than one hundred eighty days after the date the public meeting on the proposed incorporation was held under RCW
35.02.015, or the next regular business day following the one hundred eightieth day if the one hundred eightieth day is not a regular business day.