In the TEPCO's handout detailing the in-the-ground water storage ponds at Fukushima I Nuclear Power Plant that the company started to use to store extremely radioactive (beta, potentially 2 sieverts/hour) and saline waste water after the Reverse Osmosis (desalination) treatment, there was this diagram (click to enlarge):
Independent journalist Ryuichi Kino often asks questions that visibly irk the TEPCO spokesman, and he asked one such question in the press conference on April 10, 2013 as I watched live:
"So these ponds are constructed in the same way as a controlled final landfill site. Why? A controlled final landfill site is not meant to be waterproof. Why didn't you choose a covered final landfill site with concrete foundation, at least?"
There was no answer from the TEPCO spokesman other than to mumble they had their own reasons. I didn't hear any other reporter ask questions about the construction of the ponds.
Kino also reports that the company who supplied the polyethylene sheets says they are not responsible for the degradation due to radiation.
Here's Asahi Shinbun Fukushima local version (4/11/2013; part), inspired perhaps by Kino's questions:
In-the-ground water storage ponds at Fukushima I Nuclear Power Plant are constructed like a garbage disposal site. Experts say "They cannot prevent leaks."
It has been revealed by the explanation given by TEPCO that the basic structure of the in-the-ground water storage ponds which leaked one after another at Fukushima I Nuclear Power Plant is the same as a type of waste disposal site called "controlled landfill site" using waterproof sheets. Experts heavily criticize the structure, as "badly made even from the standard of a waste disposal site".
According to TEPCO, these ponds were made by first digging holes in the ground, laying the bentonite sheet first and then two layers of waterproof sheets. TEPCO emphasizes they were doing the strict quality control.
Commenting on this structure, Akio Hata, former chairman of the Japan Association on the Environmental Studies and former professor at Osaka City University, says, "It is as if you lay sheets in a pond to store contaminated water. It is impossibly pathetic considering the recent standard of disposal sites. It's wrong to even think about [using such a structure]." He suggests, "You cannot prevent all leaks. So you build a structure on the assumption that it will leak. It should be the above-ground, stainless-steel tank so that a leak can be detected easily."
The Nuclear and Industrial Safety Agency, the regulatory agency overseeing TEPCO before the Nuclear Regulatory Authority was set up, approved the plan in August 2012 to store the highly contaminated water that contained radioactive strontium and other nuclides in the in-the-ground water storage ponds. However, there is no clear legal standard for examining what type of structure would secure the safety.
Needless to say, there was no expert at NISA who knew anything about waste management. NISA took TEPCO at their word and approved the plan.
The ponds were designed and speced by TEPCO and built by Maeda Construction, who has already said such a structure is used for solid waste storage not liquid.
During the April 9, 2013 press conference, TEPCO's spokesman Mr. Ono uttered a convoluted sentence regarding the delay in announcing the leaks:
"We don't think it is not leaking, but we cannot deny the doubt that it may be leaking."
Got that? In other words, TEPCO tried very hard to find other reasons first that may be contributing to higher chloride concentration or radioactive materials in the sampled water.