Seven years after the Big Dig was declared complete, the Central Artery tunnels have sprung even bigger leaks, sticking state taxpayers with a plumbing bill as high $7 million a year, a Herald review found.

More than 16 million gallons were pumped out of the Tip O’Neill Tunnel, the Ted Williams Tunnel and the I-90 Connector annually in 2013 and 2014, according to data compiled by the Massachusetts Water Resources Authority.

And there’s no sign the deluge is slowing, as the Big Dig tunnels already hit the 16 million-gallon mark during the first six months of this year, state records show. MassDOT spokesman Michael Verseckes said the reason for the increase is unclear, but may be due to this year’s record snowfall and work crews flushing out road salt from tunnel ventilation systems.

He said the amount of water seeping into the tunnels falls within federal safety guidelines.

State officials couldn’t say exactly how much taxpayers have paid to repair the leaks since 2008, but Verseckes said the agency has ponied up between $5 million to ?$7 million annually to fix dripping tunnels.

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Last December, MassDOT issued a $12 million taxpayer-funded contract to SPS New England to fix tunnel leaks through the beginning of 2017. Wayne Capolupo, chairman and CEO of SPS New England, donated the maximum of $25,000 to Gov. Charlie Baker’s inauguration celebration earlier this year.

The Herald first reported in July 2013 that state taxpayers were on the hook for millions spent plugging tunnel cracks each year — even as the deluge hit what was then a four-year high.

Big Dig engineers previously claimed that all leaks eventually would be sealed — one report predicted by September 2005. But now state officials admit the tunnels will always leak.

Federal transportation officials must approve all MassDOT spending requests for the Central Artery/Tunnel Project Repair and Maintenance Trust Fund, which holds settlement money in connection with shoddy construction previously done on the Big Dig.

So far, the Federal Highway Administration said the agency has approved ?$127.5 million for 28 repair projects, leaving roughly $303 million in the trust.

Baker spokesman William Pitman said the governor wants to use those funds to repair the leaks.

“Governor Baker and MassDOT leadership believe the safety of those on our roadways is paramount and the administration will soon be implementing a long-range plan to use the remainder of the trust fund to address any leaks or issues impacting the long-term durability of the tunnels, in addition to a robust tunnel maintenance program that addresses water infiltration,” Pitman said.

But Baker could face roadblocks. In 2013, the state complained that federal highway officials rejected their request to tap the trust fund to fix tunnel leaks. The feds argued the tunnels were originally designed to be sealed from leakage. But because they were built so poorly, they will continue to leak — and in a Catch-22, fixing them is considered a regular maintenance cost, which is not covered by the trust.

The Herald review comes as Baker grapples with a raft of transportation challenges, including an estimated $7.3 billion to bring MBTA equipment into a state of good repair.

Baker also faces a $1 billion shortfall on the Green Line extension project, the plan to extend subway service to Somerville and Medford.

There is also a push by former Gov. Michael Dukakis and former Gov. William F. Weld for an underground rail link between Boston’s North Station and South Station, which has been estimated as high as $4 billion.