HAMPDEN, Maine — U.S. Sen. Susan Collins’ bipartisan postal reform bill is expected to go to a vote Wednesday, but time is short with the announced consolidation of the Hampden postal plant just three weeks away.

“Unless something changes, the self-imposed moratorium and changes will occur after May 15,” Tom Rizzo, spokesman for the U.S. Postal Service’s Northern New England District, said Tuesday. “At some point beyond that, we expect that a lot of these facilities’ plants [in Hampden and elsewhere around the country] will start to be closed. We don’t know what the result of this Senate bill under consideration will be. Much of the postal world is on hold and anticipating what the result will be.”

Amendments to Collins’ postal reform bill — which would keep the Hampden mail processing facility open — were handled in rapid succession Tuesday afternoon. An expected amendment by Republican Sen. John McCain, which would have almost completely gutted Collins’ bill and made it nearly identical to one sponsored by Rep. Darrell Issa, R-Calif., in the U.S. House of Representatives, was not introduced. But he did offer an amendment to set up a commission to further study the USPS proposed plant consolidations much like the military base closure commissions formed in the past. That amendment failed, according to a Collins spokeswoman.

The Senate on Tuesday accepted an amendment by Sen. Olympia Snowe, R-Maine, that would place the Postal Regulatory Commission in charge of independently verifying USPS methodology and estimated cost savings from plant consolidations.

Snowe said Tuesday the necessity of her amendment was highlighted earlier this year when the USPS claimed an “annual management savings” of $797,000 from the elimination of two management positions but later revised that figure downward to $177,000 after she questioned the figure.

“I am very pleased that the U.S. Senate unanimously accepted my common sense amendment to further strengthen the segment of the postal reform bill governing proposed consolidations for processing and distributing facilities,” Snowe said in a press release. “Indeed, the Postal Service will no longer be the judge, jury, and executioner when it comes to consolidating these critical facilities.”

An amendment to limit government conference spending passed, as did one to encourage the USPS to locate post offices in government buildings, the Collins spokeswoman said. Another amendment passed that would prohibit the USPS from closing postal facilities in vote-by-mail states before Election Day this year.

Ed Gilman, spokesman for Democratic 2nd District U.S. Rep. Mike Michaud, said that after this week, the House will next be in session the second and third week of May. While there are no plans to take up any postal bills this week, Michaud’s office was told that House leaders hope they can come together soon to find common ground between a House bill and the Senate bill now under consideration. No timeline has been given, though.

“It’s been good to see the collaboration in the Senate, and I’m hopeful the House will move a bipartisan bill forward as well,” Michaud said in a statement Tuesday afternoon. “But time is running short, and Congress needs to act quickly to clear a final bill in order to keep the Hampden facility open. If Congress can’t come together to rally behind saving these critical postal services for families and small businesses, what can they get behind?”

A key provision of Collins’ bill would require overnight delivery standards in some cases, and overnight delivery in Maine would be impossible without both the Hampden and Scarborough plants in operation.

USPS officials announced last February that the processing operation at the Eastern Maine Processing and Distribution Facility in Hampden would be consolidated, resulting in the loss of 170 of 183 jobs. Employees were told more than a month ago that the plant’s processing services would be shifted to the Southern Maine Processing and Distribution Center in Scarborough starting May 19.

“The plans and logistics have been in the works for months. We’re basically only three weeks away,” Rizzo said Tuesday, referring to USPS consolidation plans. “Right now there’s a lot of uncertainty. Things are up in the air, although decisions and plans have been made.”

Postmaster General Patrick Donahoe agreed in a letter to Collins and other senators Tuesday that the language in Collins bill would keep the Hampden facility open. About 100 other postal facilities slated for closure nationwide likely would stay open if the bill becomes law.

“I anticipate the Senate will pass the bill on Wednesday,” Collins, R-Maine, said Monday night.

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

Both Maine senators also said the slower delivery time would force businesses and other postal customers to look for other delivery options.