Port of San Diego Harbor Police Department boats combat a fire on board USS Bonhomme Richard (LHD 6) at Naval Base San Diego.
CNN  — 

The US Navy has decided to de-commission and scrap the USS Bonhomme Richard after a damage assessment found that restoring the ship would cost billions of dollars.

The amphibious assault ship was in port in San Diego in July so that it could be upgraded to accommodate the new Marine Corps F-35B jets when a massive fire broke out aboard the vessel in one of the costliest conflagrations in modern Navy history.

Navy officials said that restoring the ship would cost $2.5 billion to $3.2 billion and take five to seven years, saying that some 60% of the vessel would need to be replaced.

“Following an extensive material assessment in which various courses of action were considered and evaluated, we came to the conclusion that it is not fiscally responsible to restore her,” Secretary of the Navy Kenneth Braithwaite said in a statement.

The Navy also looked at how much it would cost to convert what remains of the Bonhomme Richard into another type of vessel, such as a hospital ship, but such a conversion could cost over $1 billion – more than building a brand-new similar ship.

De-commissioning and scrapping the vessel is estimated to cost only $30 million and take nine to 12 months to complete.

“We reached the conclusion we needed to de-commission the platform,” Rear Admiral Eric Ver Hage, the commander of the Navy Regional Maintenance Center, told reporters on a conference call Monday.

Officials said the Navy’s top leaders, including the Braithwaite and the Chief of Naval Operations Adm. Mike Gilda, made the decision last week.

Amphibious assault ships

The fire aboard the Navy warship was extinguished after raging for four days. Officials say the cause of the fire is still under investigation, but the blaze appears to be one of the costliest in modern Navy history.

The USS Bonhomme Richard cost $750 million to build when it was commissioned back in 1998, which amounts to about $1.2 billion in today’s dollars.

The US Navy no longer builds the class of ship and has replaced it with the newer America class.

A new America-class amphibious assault ship costs about $4.1 billion.

Amphibious assault ships are designed to support Marine Corps operations, carrying Marines, helicopters and jets that can transport and provide air support to a Marine expeditionary unit.