In The Stand when the graves started filling up they'd load piles of corpses on barges and dump them into the ocean. I remember thinking that was a good idea.
I know exactly where this is - there are 50,000 plastic burial vaults along I-20 east of Atlanta.
http://www.morgancountycitizen.com/?q=node/7524
The guy who owns the land got a shit-ton of calls from conspiracy nuts wanting to know how much FEMA was paying him to help ZOG/the NWO/illuminati/whatever. Yeah, no. They're burial vaults. You put them in the ground before you put the actual casket down. It keeps the ground level and prevents the casket from collapsing from age/the weight of six feet of dirt/etc.
(of course, this is all a very pat excuse, isn't it. THE REAL TRUTH IS FAR MORE SINISTER THAN "yeah, we made a bunch 'cause we had the money, and now we're sitting on them and selling them as needed. not like they're going to rust or anything.")