Looking at the survey map that they did, those locations have particularly high radiation. One particular spot measured 280 millisieverts/hour, and that's where they hope to use for water injection. (See page 3 of TEPCO handout below.)
They also managed to measure the radiation level on the stairs leading up to the 3rd floor, and it was even higher than on the stairs to the 2nd floor, almost twice as high.
TEPCO's July 28 English handout of the survey is full of interesting misspellings, but when they say "bulb", I do believe they meant "valve". To Japanese ears, the difference between "b" and "v" is close to zero, and the difference between "u" in bulb and "a" in valve is non-existent:
(Page 1)
(Page 2)
(Page 3)
One of Fukushima workers who tweets is worried about plutonium in the reactor building. He also said some time ago that the emergency radiation limit for the workers at the plant of 250 millisieverts was applied only to TEPCO employees in practice, while most of the subcontractors were limiting their workers' cumulative radiation below 100 millisieverts. TEPCO has been sending its own employees to the areas with very high radiation.
But when it comes to actually installing pipes and equipment, it will likely be the subcontractors who will have to do the job. It will be people like Mr. Watanabe who was interviewed by The Independent. I don't think TEPCO employees know much about plumbing. 1 minute of work at that highest radiation location, and you will get 2.8 millisieverts.