The shelter will help with the expected overflow of COVID-19 patients across the five-county Philadelphia region.
The shelter would be set up inside the school's recreation center on the 800-acre site.
"It's pretty big, it's about 85 to 86,000 square feet," said Christopher Spriggs, the school's acting executive director.
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The school has its own medical and dental facilities, a 2.5-megawatt generator should they lose power and even an airfield should they have to bring in patients by helicopter from across the region.
"The federal medical shelter will be here to take care of the surge capacity we can expect to handle, and also to deal with the day-to-day overflow that our hospitals, our long term care facilities may have," said Tim Boyce, executive director of Delaware County Emergency Services.
Boyce adds, the facility will start with 250 beds but could easily be expanded as needed.
"Every number we're seeing is that the worse is yet to come, so to get this thing set up within days is our goal," said Boyce.
Delaware County Congresswoman Mary Gay Scanlon spearheaded a bipartisan congressional group from the five-county region urging FEMA to approve Glen Mills School for this purpose.
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"It's important because we know Philadelphia is a hot spot, we're behind on the testing, but we're seeing hundreds of new cases every day, so it's really important that we do everything we can to be prepared," said Scanlon.
The school's acting executive director says they want to do everything they can to accommodate the effort.
"We're here to help, we're happy to serve and we're here to help out in any way during this crisis," said Spriggs.
Officials say equipment could begin arriving here as early as Friday morning, but for sure within the next few days.