Yep, they knew.

TEPCO knew about water flow two years ago

That's the headline today on NHK.

"A spokesperson for Tokyo Electric Power Company says the company has known for the past 2 years that a massive amount of groundwater was flowing beneath the Fukushima Daiichi power plant.

"Masayuki Ono said on Friday that TEPCO experts estimated hundreds of tons of the water could reach the ocean daily.

"Ono said the estimate was based on rough records of groundwater that TEPCO workers had collected.

"Until last month, TEPCO officials had denied the possibility that contaminated groundwater was leaking into the ocean.

"Ono said he is unable to explain why it took two years to disclose this fact.
Aug. 10, 2013 - Updated 07:48 UTC"

The URL, which will only work for a few hours:

http://www3.nhk.or.jp/nhkworld/english/news/20130810_99.html
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In case you missed it- I told you here I knew this- 2 years ago.  How?  Based on published information about where what kinds of radioactive materials were found.  Tinkerbelle does not go about creating Cesium 137 just for the fun of it- it had to come from someplace.  There is no "well, we're not sure" possible.

The greater question, still unasked by the media- why are our own nuclear scientists silent on this point?  I'm not one; I'm an evolutionary ecologist, which means with some training in chemistry and geology and weather.  But- the physicist in your university has to have known this- or is an idiot, take your pick.

What else do we know?  Three reactors have melted entirely through their containers, and are likely to be still melting their way to the earth's core- or will as soon as they quit pumping sea water in to cool - and leak.

And?  "Plausible deniability" is obsolete.  "Implausible deniability" is now quite adequate for government purposes.  Other world governments will back you up.