Paint splotches on sidewalk above sewer grates?

Factual Questions
1

I’ve recently noticed that here in San Francisco that there are paint splotches on the sidewalks above many of the sewer grates in the city, at least those along my walk to work. Not just a single paint splotch, but layers of different color paint splotches, indicating that this event has taken place numerous times. This past week, I noticed that the pink paint splotch I had been looking at for the past month had been splotched over with white.

It’s actually quite pretty, in an abstract sort of way. You can see a pic in an album on my Facebook page here: http://www.facebook.com/album.php?aid=2075133&id=1437254136&l=642bc38930

So, anybody know what these things are? I’m thinking maybe an indication that some sort of frequent inspection has taken place?

Thanks!

2

I was going to suggest it’s faded fish*, but from the picture it’s obviously not so I can’t help you. It does look interesting though.

*Groups paint fish next to the sewer drains, they’re supposed to be a reminder not to dump stuff down the drain. The program is called Yellow Fish Road

3

It’s late and I’m feeling cranky, so I’m going to be a little less reticent about criticizing an OP with an honest question than usual:

Caption your pictures. And link to ONE, not the entire page.

Take the picture from far enough back that we can tell what we’re looking at.

It’s obviously something done by a work crew, but without knowing its context, a dot is impossible to identify.

OK, I have made a small concession to politeness, and halved the word count in the process.

4

I’m guessing “art student project/prank”. A few years ago a bunch of students painted all the manhole covers in my city pink, just for the hell of it. This could be something similar.

5

I see similar in the UK and here it means that that drain has been cleaned or inspected.

6

They periodically spray under manhole covers for roaches around here. I would suspect that they are doing something similar, and are just marking to let the inspectors know were they’ve sprayed / cleaned / inspected.

7

In our community in Ontario they put a paint splotch on the sewer grate after they have treated that sewer with mosquito larvacides.

8

We have our winner.

The city has been using bike messengers for a few years to put insecticide in the storm drains. The color splotches indicate broadly when it was last treated.

They even have their own website.

Hey bugs, here comes the yummies!

9

In general, spray paint splotches on roads, sidewalks and grates/manhole covers indicate either a mapping of sewer/cable/pipe lines and/or that some maintenance action has taken place at that location.

10

That’s a different endeavor.

Markings to indicate underground utility locations are done with as much precision as one can muster from a can of spray paint, and there’s a whole “language” to them - red is always electric power, blue is always water, etc. They wouldn’t indicate pipes or wires with blotches to begin with - lines are marked out with painted lines in the direction of the underground service.

I’d suspect that the bug busters are just using whatever color strikes their fancy.