Why is Urban and Stormwater Runoff a problem?
Since the population was smaller, yards larger, and rain infrequent, most rain soaked into the ground and there was little concern about urban runoff caused water pollution in the Los Angeles River. Today, urban runoff is a leading causes of water pollution, since it washes off and carries away the pollutants from our roofs, lawn, gardens, sidewalks, driveways, parking lots, streets, and freeways. These pollutants includes lawn, garden, and pet wastes, trash and litter, paint, soap and grime from washed cars, oil and leaking automotive fluids, tire and brake pad dust, urban construction, maintenance, and many other aspects of modern society.
I thought waste water was treated?
Storm drains, before regulators renamed them MS4, were not meant to carry polluted sanitary sewage or toilet water, only runoff. While older cities have combined (sanitary and storm) sewer systems and large expensive treatment plants, Southern California built smaller sanitary sewage treatment facilities, while relatively clean storm water drained directly to the river. Unfortunately, polluted storm runoff has now become the next biggest problem.