The Hawaii Superferry has been kaput for about eight years, but a new audit shows the state won’t finish paying off its more than $70 million in harbor upgrades and interest for the privately owned service until 2028.

The new State Auditor’s report released today found the state on the hook for more than $45 million in vehicle-ramp and barge systems to accommodate the Superferry at Honolulu, Kahului and Kawaihae and other capital improvements.

The state also faces $24.6 million in interest on the bonds for that work and it won’t finish paying the full cost until 2028, according to the report.

Meanwhile, state leaders appropriated $50,000 to the state Department of Transportation last year to study whether it’s feasible to move forward on a new interisland ferry system. The state further received $500,000 from the U.S. DOT to assess different scenarios for a ferry system, the study also notes.

In 2009, the state Supreme Court deemed that the 2007 law that had allowed the Superferry to proceed was unconstitutional and the company filed for bankruptcy protection about two months later.