Swimmers to Be Beached : Castaic Lake: High bacteria levels are blamed for the closure of four beaches at the popular recreation area.

All four swimming areas in Castaic Lake--a popular recreation area in the Santa Clarita Valley--will close indefinitely at 5 p.m. Friday because human waste bacteria in the water is expected to reach levels considered harmful this weekend, Los Angeles County officials said Wednesday.

The closing of beaches on the west side of the lake’s lower portion, which attracts as many as 700,000 swimmers annually, is a “precautionary measure,” said Brian Roney, assistant superintendent of Castaic Lake State Recreation Area. The county-operated, state-owned facility will remain open for boating, fishing, water skiing and windsurfing, he said.

No illnesses have been reported this year from the presence of organisms in the water, health officials said, but it is expected that bacteria counts would rise during crowded summer weekends if more swimmers were allowed in the water.

More water-quality samples will be gathered Sunday, said Jack Petralia, director of environmental protection for the county Health Services Department, which ordered the closing after routine tests disclosed levels of bacteria that he said could cause severe diarrhea if the water were swallowed.

Petralia said the bacteria count was rising to dangerous levels even though the recreation area’s operators took the extra step of restricting swimming to no more than 1,100 people at a time--fewer than one-quarter of the 7,000 allowed under county guidelines.

“You’d think that should have taken care of the problem,” Petralia said. Human urine in the water on hot summer days causes excessive bacteria, he said, and the abnormal runoff from the heavy rains in February might have produced larger quantities of nutrients for the bacteria.

Castaic Lake was similarly declared off limits to swimmers during the three-day Labor Day weekend in 1990, officials said. They said they could not predict how long the swimming ban that starts Friday will remain in effect, and do not anticipate prohibiting other recreational activities in the lake.

Roney said the shutdown also means layoffs starting at the close of Friday’s shift for some of the recreation area’s 80 lifeguards and 30 cashiers and clerks.

Lifeguard Jose Maldonado, 23, of Burbank said he cried when he learned this week that he’ll lose what he calls “the greatest job in the world.” He said he must seek other part-time work while he attends school.

Another lifeguard, Sharon Elm, 26, of Mission Hills said the layoff won’t hurt her as much as full-time students because she teaches physical education at a middle school in Los Angeles’ Koreatown. Then, as an afterthought, she said, only half-jokingly, “I might be laid off too” from that job when school resumes in the fall.