Senators Maria Cantwell and Patty Murray are concerned U.S. Customs and Border Protection staffing will be inadequate to handle passengers coming through Sea-Tac Airport’s new international arrivals facility.

Cantwell and Murray, both Washington Democrats, implored Department of Homeland Security Acting Secretary Kevin McAleenan in a letter Wednesday to provide sufficient staffing or change how new systems will be implemented in order to better handle more passengers.

“While both local and national CBP staff have been actively engaged in discussions about these challenges, we remain concerned that - one year out from the completion of the IAF - there is not a clear plan to ensure an acceptable international arrivals experience,” Cantwell and Murray wrote.

Sea-Tac’s new international arrivals facility will include a 450,000 square-foot hall for baggage claim and customs processing, an 85-foot high aerial walkway to connect passengers from the south satellite to the grand hall, and a new corridor connecting passengers to concourse A. It’s expected to be completed in fall 2020.

Sea-Tac is one of the busiest and fastest growing airports in the country. With additional space, Sea-Tac expects to nearly double the number of international arrivals gates and increase passenger capacity to 2,600 passengers per hour. However, the current international arrivals terminal is already seeing peak levels of 2,000 passengers per hour in a space designed for 1,200, according to Cantwell and Murray.

RELATED: International flights expanding at Sea-Tac Airport

The senators cited modeling that used projected staffing levels and showed when the facility opens shows wait times will be two to three times longer than the goal for processing passengers.

In addition to the influx of passengers, Sea-Tac will also implement several new procedures, including introducing facial recognition software, removing automated passport control kiosks, and beginning “bags first” procedures. Cantwell and Murray worried all these changes all at once could slow processing even further and asked McAleenan to consider phasing in the measures.

“For many visitors and business travelers, their arrivals experience at Sea-Tac sets the tone for their time in the United States,” the letter read. “Long waits on the plane, in the corridor getting off the plane and in line at customs will not provide the kind of world class customer experience or welcoming tone that Sea-Tac strives to provide.”

RELATED: Sea-Tac Airport braces for busy summer travel season