A reservoir goes undercover

The Los Angeles Department of Water and Power dropped the ball Monday.

Actually, it dropped 400,000 of them.

The agency started dumping thousands of floating plastic balls into Ivanhoe Reservoir -- the dwarf sibling next door to Silver Lake Reservoir, the neighborhood's crown jewel -- to protect the drinking water supply needed for summer.

The water needs to be shaded because when sunlight mixes with the bromide and chlorine in Ivanhoe's water, the carcinogen bromate forms, said Pankaj Parekh, DWP's director for water quality compliance. Bromide is naturally present in groundwater and chlorine is used to kill bacteria, he said, but sunlight is the final ingredient in the potentially harmful mix.

The DWP drop was designed to stop the three from mingling in the 10-acre, 58-million-gallon Ivanhoe Reservoir. The 102-year-old facility serves about 600,000 customers downtown and in South Los Angeles.

Elected officials, community activists and two dozen DWP officials and maintenance workers grabbed a few balls out of a white tub and tossed them into the aquamarine pool after a brief news conference.

Pebble-heavy "plops" permeated the laughter of smiling onlookers. City Councilman Tom LaBonge shouted, "For quality of water for all of Los Angeles!" with each of three balls he chucked into the water.

At a signal from DWP General Manager David Nahai, a dozen crew members began opening dozens of white nylon bags that lined the reservoir. Each bag bulged with 2,100 balls.

Resembling a slithering stream of oversized caviar, the black balls rolled thunderously down the reservoir's slopes. "Water quality doesn't get more exciting than this," Marina J.F. Busatto, a DWP biologist, said with a smile to a colleague as she helped slide ball-filled bags to the reservoir's edge.

Within 30 minutes, a portion cordoned off in Ivanhoe was blanketed with the black balls.

"It looks like an oil spill," quipped Marilyn Oliver, 63, who has lived on a hill overlooking the reservoir for 45 years. But, she quickly added, "it's OK because it's temporary and the water quality is more important than the looks."

Open reservoirs exposed to sunlight are now rare. The area's reservoirs -- Silver Lake, Ivanhoe and Elysian -- first registered elevated levels of bromate between June and October 2007.

But state health officials said the dangers were minimal because bromate poses a small cancer risk only after consumed daily over a lifetime.