By Juli McDonald

BOSTON (CBS) – The US Postal Service says Wednesday is the last day to send things regular mail to have it arrive by Christmas. It’s the busiest time of the year for the USPS, but workers say they are up for the challenge.

Just as the rest of city begins to settle down for the night, the busy shift clocks in at the Boston Processing and Distribution Center. The entire system is a well-oiled machine – but still each year presents new trends and some challenges.

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“We’re busy year-round but during this season our volume is probably about one and a half times what it is the rest of the year,” said USPS communication specialist Steve Doherty.

That’s a whole lot of envelopes and packages, when you really consider just how much mail these machines are designed to handle every single day.

“Twenty-four-hour operation,” Doherty said. “The machines keep moving, the mail keeps flying. Especially this time of year.”

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And it really flies. Mail from all the blue collection boxes is almost instantly sorted through a machine, whipping 13,000 front facing envelopes through every hour. The Boston facility right behind South Station is used to processing millions of pieces of mail on the busiest December days. But last year was so different. It wasn’t just holiday cards and gifts, but toilet paper, and groceries, and whatever else shoppers could get without going in a store.

“We’ve seen more people going back to brick and mortar stores this year but you’re not going to see a complete reversal,” Doherty said. “A lot of people got used to shopping that way. The package volumes are going to remain up we feel through the holiday season and beyond. We’re ready for it.”

And as for expected delivery dates well into January – that’s a supply chain issue. It has to do with item availability; the mail always moves the same.

“We’ve been doing Christmas for 240 years. We know how to prepare for it. This is our season,” Doherty said.

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The postal service prepares for procrastinators, but you’ll really want to send what you can by this weekend. The 23rd is the deadline for priority mail express but you’ll be cutting it close.

Juli McDonald