Mass Burial Coffins?, Hundreds of thousands of them at FEMA site. WHY?

Location of this is exactly 33°33'57.36"N 83°29'6.26"W. These appear to be large almost coffin shaped containers suitable for disposing large amounts of degradeable waste when hermetically sealed. No need for incineration, air contamination or filters. Would also prevent ground contamination associated with mass gravesites if buried in this manner.

3. Questions,
1. What the hell are they?
2. Why have so many of them been manufactured?
3. Who is the client ordering them