I've heard that too, but to be fair rivers kind of need to run into the ocean eventually. Are they doing it excessively? Couldn't say as it's not my area of expertise.
edit: I read this again and noticed you're talking about drains. Yes, that sounds retarded and the water should go back to golf courses or something. But maybe there is bad chemical shit on the streets or something so it can't go back directly into lakes? If that's the case, time to clean that shit up.
True, you can't really avoid oil accumulation on the streets in california. That's actually what causes a significant amount of accidents on interstates because bits of oil gradually accumulate in the cracks of the roads during the hot and dry months, then rain comes and the rain settles under the oil, which rises to the surface level of the street and creates very slick spots. Would probably be difficult to filter that runoff from the drains, but otherwise that's throwing a lot of crap into the ocean which isn't good either.
Don't forget, California has a history of dumping hundreds of billions of fresh water directly into the pacific. They also are not investing heavily into rainwater capture, so a vast majority of all rain goes into drains and canals that again are dumped directly into the pacific.