Some older cities, like the Chicago area, never had a separate line for storm-water drainage because when they were originally set up, they all went into rivers, lakes, streams, etc. When they began treating waste, the grates in the streets were already connected up to the same lines, so everything winds up getting treated.
Most of the sewers in the street in the Chicago area go into the wastewater system & is treated. In areas where it does not, further away from the city, such as at least parts of Prospect Heights, you will often see either warnings spray painted by the sewer & I've also seen some sewer grates that depict fish & other things in the metal & indicating they go to a stream. Where I'm at, I'm 100% positive that it goes into the waste treatment system.
I agree with Jules.
I'm almost certain the drain in front of your house is a storm drainage and not a part of the sewer (wastewater system) line.
I line my WSM water pan with foil. Leftover water gets dumped on my lawn or garden, using a paper towel to skim any floating fat drippings. I wipe the foil with a couple of paper towels and that and any fat gets thrown into my green waste recycle container. Our waste/recycle company requests that all grease gets thrown into the green/yard trimmings container rather than the landfill garbage. The foil goes into the garbage.