The state Senate passed a bill Thursday exempting all port towns from having to cover any Steamship Authority pandemic-related budget shortfall this year, assuring the financially-strapped boat line that the commonwealth will step in to help cover expected losses.

Sponsored by Cape and Islands state Sen. Julian Cyr, the bill is an amendment to the state budget and still needs to pass the house.

But if it does, the financial burden for boat line losses will be shifted from port communities to the state, according to a press release that went out late Thursday afternoon from Senator Cyr’s office.

“Decreased ridership due to the ongoing Covid-19 pandemic has already forced the Authority to run a budget deficit to remain in operation and continue providing ferry service to the Islands,” the press release said in part. “The amendment shields the port towns from an assessment of liability for the deficiency — which could be in the millions of dollars.”

Towns responsible for covering any deficit include all six Vineyard towns, Nantucket, Falmouth, Barnstable and New Bedford.

The SSA faced an unprecedented financial crisis earlier this spring, when pandemic-related shutdowns stopped travel and caused traffic on the ferry service to plummet. Chartered by the state in 1960, the Steamship Authority is the only ferry company in the country that operates without state and federal subsidy. All operating monies come from ticket fares, giving the boat line unusual independence but leaving it vulnerable to swift changes in ridership.

Under the 1960 charter, the five port communities are liable to cover any revenue shortfalls facing the SSA at the end of the fiscal year. The boat line hasn’t had a deficit in more than half a century

But in early April, as ridership cratered and revenue declined precipitously, the SSA sought an unprecedented financial bailout from the state, claiming that the port communities could be on the hook for upwards of $50 million in shortfalls.

On Thursday the senate unanimously passed the amendment to the fiscal year 2020 supplemental budget releasing the port communities from liability.

In the press release, Mr. Cyr estimated that the current shortfall is in the range of $22 million.

“The least among us on Nantucket and Martha’s Vineyard rely on the Steamship Authority and count on its affordability — and we are determined to preserve it in these extraordinary circumstances,” Mr. Cyr said in the statement.

The amendment earned quick praise from the port communities, including Oak Bluffs town administrator Robert Whritenour and Tisbury town administrator Jay Grande.

“Our communities and local residents have been brought to our knees by the Covid-19 related economic shutdown,” Mr Writenour said in the press release. “To be facing the additional economic tsunami of a burgeoning SSA shortfall as a result of the virus is more than our small communities can bear in this difficult financial time.”

The amendment now heads to a conference committee with the house version of the FY 2020 supplemental budget, which passed on June 24.

SSA general manager Robert Davis added his thanks in the release.

“Ensuring that the burden of this epidemic does not fall on the shoulders of our port communities is of vital importance, and thankfully our local legislators have understood our unique predicament from the outset of this crisis,” Mr. Davis said in part.