The mail processing facility in Hampden would stay open under a postal reform bill now before the Senate, Sen. Susan Collins said late Monday.

A key provision of the bill would require overnight delivery standards in some instances. Overnight delivery in Maine would be impossible without both the Hampden and Scarborough plants.

In a meeting in Washington, D.C., Monday evening, Postmaster General Patrick Donahoe agreed that this language, drafted by Collins, would keep the Hampden facility open, the senator said. About 100 other postal facilities slated for closure nationwide likely would stay open if the bill becomes law.

The Senate is scheduled to vote on the reform bill Wednesday. “I anticipate the Senate will pass the bill on Wednesday,” Collins said Monday night.

In February, federal officials announced that the U.S. Postal Service Eastern Maine Processing and Distribution Facility would be consolidated, resulting in only 13 of the 183 employees being retained. The plant’s processing services would be consolidated and shifted to the Southern Maine Processing and Distribution Center in Scarborough starting May 19, employees were told at that time.

Closing the Hampden facility makes no sense, Collins said, because mail from Caribou to Madawaska would have to make a trip to Scarborough only to return to Aroostook County, a round trip of more than 600 miles.

With mail delivery taking so long, businesses and other postal customers would look for other delivery options, further worsening the Postal Service’s woes, she said.

That is the message she conveyed to Postmaster Donahoe, using a map of Maine to make the point.

“It is great news for the jobs at the plant, but equally important, it is great news for the businesses and residents of northern, eastern, central and some parts of western Maine,” Collins said of retaining the Hampden facility.

The bipartisan 21st Century Postal Service Act is authored by Sens. Collins, Joe Lieberman, I-Conn.; Tom Carper, D-Del.; and Scott Brown, R-Mass. It would also make changes to the agency’s pension system to allow the postal service to set aside less money to prefund pension obligations.