Beaches along a two-mile stretch of coast south of Ballona Creek were reopened to swimming and surfing two days after an estimated half-million gallons of raw sewage spilled into a storm drain that leads to a tributary of the creek.

Los Angeles County Department of Public Health officials announced that warning signs posted at Ballona Creek near Marina del Rey and surrounding areas were removed as of about 2 p.m. Friday, Oct. 1 after water samples taken in the two days following the spill showed bacteria levels within normal ranges. The department had posted the advisory signs for swimmers, surfers and recreational users at areas such as Dockweiler State Beach in Playa del Rey as a precautionary measure.

“Our first priority is to protect the health and safety of the people who visit the beach and water areas,” Jonathan Fielding, director of public health and county health officer, said following the issuance of the advisory. “Once we determine bacteria levels in the water have returned to normal, we will remove the beach advisory.”

The Los Angeles Department of Public Works had received a report at 12:38 p.m. Sept. 29 of a sewage overflow at 6161 W. Centinela Ave., near Sepulveda Boulevard, said Lauren Skinner, public works spokeswoman. Approximately 500,000 gallons of sewage reportedly entered an adjacent storm drain that discharges into the Sepulveda channel, which flows to Ballona Creek and the ocean, Skinner said.

The public health department placed the beach warning signs after officials were notified that the discharge could enter the ocean. County health officials anticipated that the advisory could have been in effect until 3 p.m. Saturday, Oct. 2, but lifted the warning earlier after test samples found bacteria to be within normal ranges.

Skinner noted that the water samples in the area showed “very minimal impact if at all.”

The sewage discharge was believed to be due to an accumulation of debris that caused a blockage in a manhole from a small pipe that extends from a larger pipe from a Mesmer Avenue pumping station in Culver City, Skinner explained. The spill occurred at a site where the Culver City line meets with the city of Los Angeles line, she said.

An investigation was underway to determine which agency has the responsibility, but the city of L.A. spearheaded the clean-up effort and dispatched crews to the scene, she said. The crews managed to stop the sewage flow by 5:30 p.m. and removed the blockage by 8 p.m. Sept. 29, she said.

Asked about the significance of the spill, Adel Hagekhalil, Bureau of Sanitation assistant director, said the city gauges such incidents based on their impacts on the environment.

“Based on the sampling results there was minimal impact on water quality,” Hagekhalil responded.

Despite the estimated figure of 500,000 gallons, the seriousness of the spill is considered to be “reasonably average” because most of the sewage was contained in the channel and the pipe system leading to Ballona Creek, the assistant director said. There was no reported damage to the streets.

He attributed the minimal impact to the work of crews that initiated an immediate clean-up. The crews worked “around-the-clock” to contain all the water, which was pumped into tankers and put back into the sewer system, he said. The area was then pressure washed and sanitized.

The clean-up was expected to be fully completed by Wednesday, Oct. 6.

In regards to the occurrence of such a large sewage spill, Hagekhalil noted that the city has improved the performance of its sewer system and has experienced a more than 80 percent reduction in the number of reported sewage spills since 2001. Though large spills are an “anomaly,” the sanitation bureau is committed to protecting public safety and continues to review its practices to see where improvements can be made, he said.

Skinner said the city is also looking to work with Culver City to discuss potential improvements.

“We will be using this as an opportunity to work with Culver City, our valued neighbor, to discuss best management practices,” she said.