I have and will never be a fan of cemeteries, they just take too much space, if the loved ones wants to visit a dead relative, why dont they just cremate and store the ashes in a container and keep them in their houses. Lands are becoming expensive and there is lots of overcrowding almost everywhere.
Existing cemeteries should be destroyed and new homes, schools built in their place. No more new cemeteries. They serve no purpose.
Waste of resources.
Human corpses should be cremated and ashes used in ag industries, or given back to families if desired.
There's a much simpler way, which is just to dump all the coffins at the edges of Washington DC. Over time they can level the mound say at 300' higher than the initial ground level. Then the trucks drive up, and dump their loads.
It might take a decade or two but the swamp would be filled in, and the swamp creatures would be no more.