(UPDATE) Here comes IAEA, pledging support to Japanese government in dealing with contaminated water leak at Fukushima I Nuke Plant. Jiji Tsushin in English reports "IAEA Ready to Help TEPCO over Tainted Water Leak". ("Tainted"??)
The press decided to simply quote the government official, despite their misgivings.
There's a word for that in Japanese: げたを預ける (to leave a matter completely in someone else's hand)
It is rather apparent if you watch the video of the press conference on August 7, 2013 that reporters from Japanese press and foreign press either did not understand what Mr. Tatsuya Shinkawa, official in charge of dealing with the Fukushima I Nuke Plant accident at the Agency of Natural Resources and Energy at METI, said about the "300 tonnes leak", or had varying degrees of doubt as to the veracity of the numbers.
Particularly when Mr. Shinkawa, to answer the persistent questions from the reporters throughout the press conference from Asahi, Yomiuri, Mainichi, NHK, Wall Street Journal, AP and others, had to repeatedly cite TEPCO's numbers which had nothing to do with the actual or potential leak:
TEPCO told us they will start drawing 100 tonnes of water each day from three wells.
On hearing that from TEPCO, the conclusion at his place of work, the most elite ministry of the Japanese government with Japan's best and brightest, was that this water must be leaking right now, because the wells were yet to be operational.
Judging by the questions and how the reporters asked them, it is clear that they didn't buy Shinkawa's "assumption" or hypothesis (仮定), the word Shinkawa repeatedly used.
But what happened when the reporters wrote up their articles for their respective papers?
With the exception of Tokyo Shinbun reporter, they made no reference to how Mr. Tatsukawa came up with the number ("assumption" from TEPCO's numbers which were not about the amount of leak), and treated Tatsukawa's remark at face value, as a given fact that officially came from the national government.
If it is wrong, it's Tatsukawa's and the government's problem, not the reporters. What can go wrong by citing the government official? And in the process of quoting the government official, so what the groundwater morphed into either "highly contaminated water" or "nuclear waste water"? What minor difference!
The amount of groundwater flowing into the ocean is unknown. It could be 300 tonnes, it could be more. It could be less. The degree of contamination is known, to the extent of the actual monitoring of the seawater right outside the water intakes at the embankment; the data shows radioactive cesium in slightly over 100 Bq per liter at the maximum, no radioactive iodine.
The highest measurement of radioactive cesium is in front of the Reactor 3 water intake. At other locations, the density of cesium is between 10 and 50 percent of the legally allowable density in discharge water from a nuclear power plant. Tritium and all-beta are not regularly monitored. (Here's the latest seawater monitoring data, released by TEPCO on August 10, 2013.)
The video archive of the August 7, 2013 press conference at IWJ: http://iwj.co.jp/wj/open/archives/95298