Ala. Code § 11-81-121

In exercising the powers conferred by Sections 11-81-119 and 11-81-120, it shall not be necessary to make a separate issue of refunding bonds with respect to each outstanding issue, but two or more of such outstanding issues or portions thereof may be grouped together in a single refunding issue, in which event all assessments thereafter collected with respect to any of the improvements financed by the separate issues or the proper proportionate part thereof shall be applicable to the payment of such refunding bonds.