Maybe not horrible...most well sites have tanks on them, usually one bank for temporary crude oil storage and another for contaminated water (from natural ground water that comes with the oil, not fracking water).  However, there are also process vessels of various types that are often called "tanks" that also handle oil and gas.  So, which one was actually the culprit is lost in the article, and the photos don't really help.

You are correct about the fracking part.  There's no such thing as a "fracking site"...but, regardless, only a random Twitter user and the person assigning tags appear to have made that incorrect assertion.