1.6E+6 Bq/m3 of Tritium was measured from a deep well in the plant area of Fukushima (500m away from the reactor buildings), Tepco announced in their press conference of 4/4/2012.
Last time they measured beta nuclides from the same well on 11/19/2011, tritium was ND, which shows the underground contamination has been expanding since then.
From the press release of 4/4/2012, Tepco measured 1.3E+6 Bq/m3 of tritium from the sub drain of reactor 2, and 1.8E+6 Bq/m3 from the one of reactor5, which are the same level as what they measured from the deep well.
As to tritium, underground water is as contaminated as sub drain of reactors.
Iori Mochizuki