(UPDATE) TEPCO's handout at today's press conference shows that even if they didn't have the exact measurement of strontium, they had all-beta measurement that included strontium of the May 24, 2013 sample.
Compared to the December 8, 2012 sample that had 150 Bq/liter of all-beta, the May 24, 2013 sample had 1,900 Bq/liter of all-beta, one order of magnitude more. The amount of tritium also jumped by one order of magnitude. At that point, TEPCO could have said something. Instead, they again withheld the information until they had the strontium amount correct.
From TEPCO's handout for the press (6/19/2013), red rectangles added, to show the observation pit in question (No.1):
During the meeting of the Nuclear Regulatory Authority on June 19, 2013, Commissioner Shimazaki raised the issue of this tardy reporting by TEPCO, finding it problematic. But the NRA chairman Tanaka put in some kind words for TEPCO saying it would take about a month to fix the amount of strontium.
Yomiuri Shinbun (6/19/2013) reports that TEPCO was in possession of the May 24, 2013 data disclosed today (see above) as early as June 3, 2013.
TEPCO being TEPCO. Same old story that never seems to end.
500,000 Bq/liter of tritium from the water sample from May 2013, one order of magnitude higher than the sample taken in December last year (29,000 Bq/liter).
Location: Between Reactor 1's turbine building and Reactor 2's turbine building. (Compared to two other observation holes on the east side of the turbine buildings, this one shows consistently higher levels of tritium and all beta.)
1,000 Bq/liter of strontium.
Very low concentration of radioactive cesium.
(So, TEPCO has known this since late May.)
Source of contamination: past leak from Reactor 2 screen pump room. The contaminated water leak from April 2011 at Reactor 2 water intake.
Soil amendment along the east side (ocean side) of the turbine buildings, fill the gap underground.
(So, these trenches are still filled with contaminated water... All TEPCO did was to plug the exit.)
Sankei Shinbun reporter is asking, "If tritium, strontium have been discovered in the groundwater which naturally flows into the ocean, is it safe to assume this contaminated water has been flowing into the ocean?"
Did you disclose the discoveries in May and early June, he asks.
TEPCO says it was only yesterday they got the strontium data.
Press conference live feed: http://www.tepco.co.jp/tepconews/streaming/index-j.html