Maryland’s director on a controversial state plan to widen the Capital Beltway and Interstate 270 retired Dec. 31, in the middle of one of the largest procurements in state history.

The Maryland Department of Transportation confirmed Lisa B. Choplin’s retirement but declined to comment on the timing, one week after companies on Dec. 23 had submitted the first part of their highway widening proposals. The second parts are due Friday.

The expansion plan is one of Gov. Larry Hogan’s signature infrastructure projects. Hogan (R) has said teams of companies will build and operate toll lanes on both highways, and rebuild the free general purpose lanes, at no net cost to the state, in exchange for keeping most of the toll revenue over 50 years.

With contracts valued at $9 billion to $11 billion, it would be one of the largest public-private partnerships ever in the United States.

Choplin, 55, who was the public face of the project, did not return voice-mail and text messages left Wednesday. Her retirement was first reported by IJGlobal Project Finance and Infrastructure Journal.

Terry Owens, a project spokesman, declined to say why Choplin had left in the middle of such a huge procurement.

“Lisa was an amazing and dedicated public servant who retired from state service after 30 years as eligible,” Owens wrote in an email.

He said the state still has a “group of experts from both the public and private sector.” Choplin’s replacement has not been chosen, he said.

Supporters of the highway expansion plan say it would alleviate stifling traffic congestion and help the Maryland suburbs remain economically competitive with Northern Virginia, which already has express toll lanes. Opponents, including some who have said they’re considering a lawsuit, say the highway widening would destroy surrounding homes, parkland and streams, and would be unfair to motorists who can’t afford to pay tolls.

Julie Tate contributed to this report.

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