The man who oversaw more than $45 million in upgrades to the port of Portland and helped transform it into a modern shipping terminal has resigned.

John Henshaw, executive director of the Maine Port Authority, stepped down Wednesday after a decade of leading the state agency.

During his tenure, Henshaw oversaw the expansion of the International Marine Terminal in Portland and is credited with helping convince Eimskip, an Icelandic shipping company, to locate its North American headquarters in Maine. Recently, Henshaw pushed for a waterfront zoning change to allow a cold-storage warehouse near the container terminal.

“He did an outstanding job for the port authority, including being heavily involved in many milestones at the International Marine Terminal,” said Ted Talbot, spokesman for the Maine Department of Transportation. The authority is an office within the MDOT that oversees Maine’s three commercial ports in Portland, Searsport and Eastport.

“We wish him all the luck in the world for his future endeavors, we were lucky to have him,” Talbot said.

Henshaw submitted his resignation Sept. 7. Wednesday was his last day in the office.

“The future appears bright for the port authority,” Henshaw wrote in his resignation letter. “There will be some new and exciting developments announced at the International Marine Terminal in Portland in the coming weeks and months. I believe the momentum is there to carry the facility far into the future. Searsport and Eastport should see some positive developments in the future as well.”

Henshaw did not respond to an interview request Thursday.

One of his major contributions was the revitalization of the International Marine Terminal after the company that had been providing container service there left during the recession that began in 2008. In 2009, when the authority took over management of the shipping terminal from the city of Portland, it was used for snow storage.

Since then, more than $45 million has been invested to upgrade and expand the port, including its crane system and a rail spur directly to the container terminal. More improvements worth up to $15.5 million are planned in the near future.

Investment in the port attracted Eimskip, which has steadily added calls to Portland every year and plans to have weekly container service by 2020.

Over the past year, Henshaw helped get a Portland zoning change approved that allows for construction of a large cold-storage warehouse on the waterfront near the marine terminal worth more than $20 million. The zoning change was fiercely opposed by nearby residents upset with the size of the building.

Matt Burns, director of ports and marine at the MDOT, will take over as acting executive director at the port authority while the board of directors starts a search for a permanent replacement, Talbot said.

Peter McGuire can be contacted at 791-6325 or at:

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Twitter: @PeteL_McGuire