The PA Department of Environmental Protection, that’s who!

We usually call them “storm drains” but others use the term “catch basins” or “inlets.” In any case, that’s where runoff from streets goes through a grill and disappears from our sight. But then were does it go? It should drain by gravity though a pipe system and eventually flow into a stream. That’s a problem for the stream, because street runoff can be polluted, e.g, by car and animal wastes.

But when water is able to remain standing in the storm drain, it provides an ideal habitat for mosquitoes to breed! Then those storm drains need to be “treated” (with a larvicide like Bti) to keep larvae from maturing there into adult mosquitoes. Here’s what PA DEP says (you have to keep refreshing the URL in your browser to find this photo and commentary):