watering the river

[topaz]

slow day for the Bedford FD?, originally uploaded by qwrrty.

My usual route to work takes me over the Concord River between Carlisle and Bedford. On Friday I was enjoying a particularly lovely ride as I crossed the bridge, when I noticed that there was a Bedford fire engine parked at the boat launch... watering the river.

Here they are. See? Look! There's the water! Going into the river!

Any hints what might be going on here? The closest thing I could think of was some kind of water-laundering scheme, but I got hung up on the details. I'm open to ideas here.