A California appeals court has sided with environmentalists in a decision that blames Los Angeles County and its flood control district for sending polluted runoff into the Pacific Ocean.

The 9th Circuit Court of Appeals ruled Thursday that the county is responsible for the heavily polluted storm water flowing untreated each year down the Los Angeles and San Gabriel rivers.

The Natural Resources Defense Council and Santa Monica Baykeeper environmental groups say the ruling is a turning point in the battle for clean water. Council attorney Aaron Colangelo says the county must now eliminate the flow of pollutants.

The Los Angeles Times says the Flood Control District argued its channels were simply conduits for upstream polluters, but the court says the district controls the flow to the ocean.