Judging by the all-beta numbers, the leaked waste water (extremely high in beta nuclides but not so much in gamma nuclides) hasn't reached the drains or the ocean in great quantities yet.
TEPCO's handout for the press in English, 9/4/2013:
(Click to enlarge)
The highest all-beta reading of 700 Bq/L is at B-3, where the B Drain and C Drain meet. At the ocean at T-2, all-beta is ND.
The number to look out for for all-beta is in tens of thousands of becquerels per liter (i.e. number in the order of 1.0E+05 per liter) or higher for the water in the drains.
The last time the Reverse Osmosis (RO) waste water leaked from the Reverse Osmosis Apparatus itself and reached the ocean (March 2012), all-beta in the water in the drain reached 86,000 Bq/L. Once it reached the ocean, the contamination was diluted to less than 1/1000, and only 55 Bq/L of all-beta was detected at T-2 location in the diagram above. However, when the water leaked from the Evaporative Condensation Apparatus in December 2011, the number for all-beta was four orders of magnitude bigger for the drain water (1.0E+0.5 per cubic centimeter).
So far the number like those hasn't happened.