The question of who is responsible for cleaning up Los Angeles County's storm water goes before the U.S. Supreme Court Tuesday.

The nine justices must decide whether the Los Angeles County Flood Control District is liable for billions of gallons of urban runoff that pollute inland rivers, streams, lakes and the ocean, or if a collective of 85 cities and 140 unincorporated areas are at fault.

If after hearing oral arguments, the high court rules against the District, it would cost "tens of billions of dollars" to build diversion pipes and treatment projects, according to the county Flood Control District, a special district governed by the county Board of Supervisors.

The county is hoping that the court will overturn a Ninth Circuit Court of Appeals ruling, which held the District liable.

The case began in 2008 when the Natural Resources Defense Council and the the Santa Monica Baykeeper (now known as the Los Angeles Waterkeeper) filed suit alleging the county was responsible for the urban runoff that picks up bacteria from dog feces, metals from brake pads and pesticides from lawns as it flows through the Los Angeles and San Gabriel rivers to the ocean.

"The county Flood Control District likes to point the finger, to lay blame elsewhere," said Steve Fleischli, water program director and senior attorney for the NRDC in Washington on Monday. "They would say even if their storm water discharges were on fire, they would not be liable. We think that is untenable."

Studies say urban runoff sickens 640,000 to 1.4 million people who visit L.A. and Orange County beaches each year, Fleischli said. Mostly, swimmers come down with diarrhea, sore throats, pink eye or fever, he said.

While few argue that storm water pollution is a serious problem, few can agree on who should clean it up.

The county says it is not solely responsible because it doesn't produce the pollution but only carries it away. Like Internet Service Providers, it should not be held liable for objectionable content.

The district, which was founded in 1915, moves storm water through Southern California's two major urban rivers as well as thousands of miles of concrete washes and channels, keeping homes and property safe from flooding.

"We believe that the argument put forth by the NRDC is flawed in that it confuses the conveyance of polluted water with the creation of polluted water," said Gail Farber, chief engineer of the District and director of the Los Angeles County Department of Public Works.

"We recognize the complexity and significance of the questions before the justices, and are confident that, when the facts of this case are presented, the court will support our position," she added.

The complex case rests on a narrow definition of what is a pollution discharge.

Since the case involves high levels of mercury, fecal bacteria and metals detected at the end of the L.A. River near Long Beach and in the Whittier Narrows area of the San Gabriel River, some say the materials are not "discharges" but snapshots of pollution from various upstream sources.

Storm drains from some 32 different cities empty into the Los Angeles River, while 28 cities use the San Gabriel River for discharge, Fleischli said.

"You have multiple inputs," said Ray Tahir, a principle with Tecs Environmental, a Pasadena-based environmental consulting firm. "And I'm not just talking about cites. There are industrial facilities ... that also discharge into receiving waters. Then you have nonpoint discharges (lawns, animal waste, motor oil and brake linings from roadways) coming from unknown sources. So how do you know who caused what?"

Tahir predicts the Supreme Court will rule in favor of the county because it likes to clear up confusion created by the Ninth Circuit. The cities he represents, including Duarte, Baldwin Park, Glendora, San Dimas, Claremont, Irwindale, Gardena, Lawndale, Carson, Compton and Pico Rivera, favor the county because they see the county Flood Control District as an ally. They also believe if the county District loses, it will turn around and sue the cities for the cleanup costs.

Both the League of California Cities and National Governors Association filed friend of the court briefs with the county.

"A win would validate our current approach," said Gary Hildebrand, assistant deputy director of the county Department of Public Works. "That it is a collective effort of all municipalities, not just an individual agency that is responsible."

A ruling is not expected until sometime in the spring.

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