Swimmers Throw In the Towel Over Ban : Castaic Lake: Restrictions due to contamination concerns help cut the holiday crowd by 90%.

Castaic Lake’s beaches were virtually empty this Labor Day weekend and its lawns only slightly more crowded, the result of a holiday swimming ban and a restriction on the number of weekend visitors to the popular lake.

The measures to limit use of the park, instituted by the county after a water test in July and another in August found potentially harmful bacteria in the lake’s designated swimming areas, succeeded in cutting attendance by about 90% on Labor Day, said Charles Graham, the lake’s lifeguard chief. Graham estimated that 3,000 people visited the lake Monday, compared with about 35,000 on most Labor Days.

Windsurfers, paddle boats and canoes still dotted the water Monday on the lower part of Castaic Lake, near the swimming areas. But the swimming areas, blocked to beach-goers by a line of plastic yellow tape reading “Caution,” were empty. And the beaches were populated only by a few hardy suntan seekers willing to brave the rays without the relief of the water.

Luisa Karapetyan, 16, said she and her parents knew of the swimming ban before they came to the lake but were willing nonetheless to pay the $4-per-car admission charge. “I can’t swim anyway,” she said as she sat in near solitude in the midday sun.

Others were less stoic. “It’s too hot to sit down here and not be able to swim,” Toni DuPont, 39, said as she and a friend packed up their beach towel and prepared to leave after two hours in the sun.

DuPont said she did not learn of the swimming ban until after she paid to enter the area, parked, and walked down to the shore. “They didn’t tell us,” she said. “They just took our four bucks.”

Lifeguards watching the nearly empty beach said they were less worried Monday about drownings, but were concerned about the angry looks directed at them by those deterred from jumping in the lake to cool off from the blazing sun. “It’s a lot easier,” said lifeguard Steve Dixon, 22, of Tarzana. “But, you’ve got to kind of watch your back.”

The county installed a chain-link fence around the lake a month ago and began restricting the number of visitors by prohibiting people from walking into the area on weekends free of charge, making the size of the weekend crowd limited by the area’s 1,500-space parking lot.

County officials also kept the number of weekend swimmers to about 800 to reduce bacterial contamination in the lake’s shallow areas, said Fred Elam, the senior lifeguard in charge of the lower lake.

The county’s Department of Health and Department of Parks and Recreation on Friday announced a ban on swimming during the traditionally busy Labor Day weekend because merely restricting the number of people going into the lake would be too difficult, Elam said.

Castaic Lake actually is two bodies of water separated by a dam. The 2,235-acre upper lake has 29 miles of shoreline and no swimming areas. The 197-acre lower lake has three miles of shoreline, the western half of which is set aside for swimming. Boating is permitted on both lakes and was not affected by the swimming ban, Elam said.

Graham, while stressing that he was not aware of the details of the county’s August water quality test, suggested that it was a poor indicator of the lake water’s bacterial content because it was conducted in a shallow area on a day when it was especially crowded with swimmers.

“I would venture to say there’s not a lake in the whole wide world that would pass that test,” he said.

County health officials could not be reached Monday for comment. But Curt Robertson, a spokesman for the Parks and Recreation Department, said he thought health officials were “being extra cautious. That’s sort of the way we’ve been approaching this.”