A special assessment under this chapter shall be levied only by vote of a majority of the qualified voters of the municipality voting at an annual or special meeting duly warned for that purpose. However, the question need not be submitted to the voters if all of the owners of record of property to be assessed, or of any interest therein, other than mortgagees or lien holders, consent in writing to the assessment. Either the vote or the consent shall include approval of the method of apportionment of the assessment. (Added 1969, No. 170 (Adj. Sess.), § 10, eff. March 2, 1970.)