This chapter provides an alternative procedure for authorizing assessments pursuant to this division. It is not intended to alter or restrict authority to authorize assessments pursuant to other provisions of this division in any way. This chapter does not apply to proceedings to finance public facilities unless 80 percent or more of the district is developed for residential, commercial, or industrial use at the time that proceedings are commenced. This chapter shall not be used for the acquisition of existing works, appliances, or property except insofar as the acquisition is incidental to a proposed improvement not already installed.