There is a strange site on the net entitled The Buddhization of America.
What is the significance of burying tantric vases?
It is the act of defiling the land and provoking God's judgment.
What damage does it do when they dump the mandalas off Newport Beach and Malibu?
It is the act of defiling the waters and provoking God's judgment.
Too bad they left out the stupas and the prayer wheels.
For one authoritative list of peace vase locations in the US, see: http://www.siddharthasintent.org/peace/n_amarica/us.htm