Transcript for Work crews repair hole at the largest nuclear waste site in America

evening, the concern after that scare at a nuclear site in the west. Tonight, our correspondent asking, were there warning signs miss? ABC's Matt Gutman on the scene. Reporter: Tonight, heavy equipment stuffing that radioactive hole with hundreds of tons of dirt, all meant to prevent radioactive particles from spreading. I am extremely concerned about what happened yesterday and how the department of energy can give us confidence that this will not happen again. Reporter: It's something the department of energy can't do, after learning the tunnel was built solely of timber instead of concrete and steel as it originally said. We don't know exactly what could be causing it. Reporter: What's more, a 2015 study commissioned by the department of energy itself warned of a collapse at the site, but nothing was done. Okay, so is that what happened here, that maybe you took your eye off of this particular tunnel because you were looking at so many other projects? Got a lot of different projects that we have to look at. In retrospect, was that a mistake? Um, no. Perhaps what's most disturbing, David, there are hundreds of feet more of this wooden tunnel that could be rotting away and officials admit they still don't have a plan to prevent future collapses. David.

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