Sunday’s heavy downpours resulted in some 8.8 million gallons of rain-induced sewer spills in Windward Oahu, keeping city crews busy and resulting in numerous water advisories for the area.

The bulk of it, an estimated 6.5 million gallons of sewage, flowed from the Kaneohe Pretreatment facility Sunday afternoon, continuing until 12:20 a.m. Monday, according to the city Department of Environmental Services. The public is advised to stay out of the waters of Kawa Stream near the facility.

An estimated 2.2 million gallons of sewage flowed from the Ahuimanu Pretreatment Facility on Sunday, continuing until 12:05 a.m. Monday.

Another 63,765 gallons flowed from a manhole fronting 137 Popoia Road behind Buzz’s Steakhouse in Kailua, near where Kaelepulu Stream empties into Kailua Beach Park, which the public is advised to avoid. In addition, 35,630 gallons flowed from two sites on Kawailoa Road in Kailua. The city recovered about 43 percent of that spill.

Smaller, but still significant, was another 1,200-gallon spill into Kaneohe Bay from two manholes near 45-1072 Grote Road on Sunday, and the public is advised to remain out of waters between Bayside Place and Mikiola Drive.

“The entire windward side, the collection system, the pump stations, the treatment plant, it was quadruple in flow,” said Lori Kahikina, director of the Department of Environmental Services. “My understanding is this was an unprecedented amount of rain.”

The storm, which lasted from Saturday evening into Sunday morning, produced almost 12 inches of rain in Ahuimanu, almost 13 inches in Kualoa and 8.4 inches in the Kaneohe area in a 24-hour period, according to the National Weather Service. The total at Ahuimanu was 160 percent of the February average.

While the windward Oahu spill is far short of the 48 million gallons of raw sewage that spilled into Waikiki following a ruptured sewer line in 2006, it is still equivalent to about 12 or 13 Olympic-sized swimming pools.

Kahikina said the city has not “gotten to the bottom” of where the sewage is entering coastal waters, but that the gravity sewer tunnel under construction connecting the Kaneohe and Kailua wastewater treatment plants should help minimize spills in the future. The tunnel, expected to be completed by summer, is designed to store large amounts of rainwater.

At the same time, she reminded residents and businesses not to divert rain­water into the city’s sewer system.

On Sunday, the state Health Department issued wastewater discharge advisories for Kailua Beach and Kaneohe Bay, which remained in effect Thursday evening.

The state also issued numerous brown water advisories on Wednesday, which remained in effect Thursday evening, for Kailua and Lani­kai beach parks, in addition to the North Shore of Oahu.

Susan Wurtzburg spent Thursday morning cleaning Kailua Beach Park with her dog, Jet, as a volunteer for 808 Cleanups.

“The water looked horrible,” she said. “It looked very unattractive.”

She warned a family with a small child not to go into the water due to the water advisories. She cleaned up about 10 pounds of plastic trash and debris from the shore, including a capped syringe that she suspects drifted down from the stream.

The public is advised to stay out of floodwaters and stormwater runoff due to possible contamination from cesspools, sewers, manholes, pesticides, animal fecal matter, dead animals, pathogens, chemicals and associated flood debris. While not all coastal areas may be affected by runoff, it is best to stay out if the water is brown.

Warning signs have been posted at affected beaches. Updates on water advisories from the health department’s clean water branch are available at 808ne.ws/cwbadv.