What was this?

[magid]

An dark green SUV or small truck (didn't get a clear look), with USGS on the side (not sure if its the one at usgs.com), pulling a trailer with four large cannisters of something just stopped in the middle of the street outside my window. Two guys wearing reflective vests got out. One steadied a reversible slow/stop sign on a long handle while the other took a thing attached to a long black hose that ended in something that looked like an extra-long rigid vacuum attachment (and sounded rather like one, too), presumable attached to one of the cannisters at the other end. He started at the other side of the street, carefully going in a straight line across the street. When he got halfway, he pushed rather than pulled it the rest of the way, so I could see that it had some kind of a flat blade at the end. It left no visible mark at all. As soon as he got to my side of the street, they put everything back in the trailer, hopped back in the truck, and drove off.