It is hard to gauge the size of it because despite all the green grass you see around it, right under it is black. There is no way to tell how much went into the river either... The flow was big enough to push over grass the whole path. There was markers with towels that may account for days, weeks, hard to say but they were in multiple pools that were up to a foot deep and running down toward the river so even if it was days there was a good number of towels in different areas further and further toward the river.
http://bsnorrell.blogspot.com/2011/07/oil-spill-into-cutback-river-blackfeet.html
