Cost overruns threaten what lawmakers and Navy officials have called “once-in-a-generation” shipyard modernization, according to a recent report by federal auditors.

The Navy’s 20-year, $21 billion plan to modernize the four public shipyards could falter due to cost overruns if the service fails to plan ahead.

The General Accounting Office cites projects at Portsmouth and Hawaii that are expected to be more than double their original estimates. 

In 2018, the Navy unveiled The Shipyard Infrastructure Optimization Program’s (SIOP), which has been dubbed by Navy officials and Congress as a “once-in-a-generation” modernization of its outdated public shipyards.

Auditors say the Navy still hasn’t created a budget to accounf for the full 20 years. Five years into the plan, it also hasn’t selected all of the projects it will fund, according to the report.

Plans are already underway to expand dry docks at the Norfolk Naval Shipyard, which will allow it to work on the new Ford Class Aircraft carriers.

Norfolk is the oldest shipyard in the country. The report says it is also the public shipyard most vulnerable to climate change.

The Navy hasn’t submitted a budget for how the shipyard will offset the effects of flooding.

In its response, the Navy says it is working to produce a final budget by 2025.