A Bible Quote for Everything

I came across this article on mountaintop removal (MTR) and was absolutely stupefied by this tidbit, as reported:

What could possibly justify mountaintop removal? In this region of Bible-believing Christians, some mining company representatives quote Scripture in their own defense: “Every valley shall be filled in, every mountain and hill shall be made low; the rugged land shall be made a plain, the rough country, a broad valley” (Is 40:4).

I don't know where to start. I did read the rest of Isaiah 40, and I'm pretty sure it isn't about MTR.