Conn. Gen. Stat. § 7-251: New and supplementary assessments.

If any assessment is not valid or enforceable for any reason, a new assessment may be made. If any assessment is made which is not sufficient to cover the entire cost of the work to be paid for by such assessment, a supplementary assessment may be made by the water pollution control authority against those properties previously assessed to the end that a sum sufficient to pay the cost of such work may be obtained, provided no such supplementary assessment, together with the original assessment, shall exceed the value of the special benefit to accrue to the property against which the benefit is assessed.