Storm forced millions of gallons of sewer water to spill in Windward Oahu

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This weekend’s rainstorm caused millions of gallons of sewer water to spill in Windward Oahu.

A brown water advisory is posted for Kailua and Lanikai beaches, and along with Oahu’s North Shore.

The city Department of Environmental Services released start and stop times of rain-induced sewer spills, along with the amounts recovered by crews.

The breakdown includes 2.18 million gallons spilled from the Ahuimanu Pretreatment Facility and 6.5 million gallons spilled from the Kaneohe Pretreatment Facility.

The city says water that’s supposed to go into the storm drains is getting in the sewer lines, so officials need to figure out how to stop that from happening.

Four days after the massive spill, warning signs are still posted at Kalama Beach in Kailua telling people to stay out of the water.

For Kaneohe resident Dick Matsumoto, remnants of the spill are still in his home.

He says sewage was gushing out of the manhole right outside his house.

“You can see all the brown debris all in front of our driveway,” Matsumoto said. “It smelled in the house.”

The city says because of the weekend’s downpour, the pretreatment plants in Kaneohe and Ahuimanu were overwhelmed.

“That flow is somehow getting into our system and I’m not quite sure how to stop it,” said Lori Kahikina, director of the city Department of Environmental Services.

With more rain on the way, the city says it’s draining out the retention basin at the pretreatment facilities, hoping they don’t get overwhelmed again.

“That’s what we’re doing to prepare is draining all of that down to make sure all of our tanks are available for increased rainfall coming in,” Kahikina said.

Officials are also asking residents not to let storm water drain into the sewage lines by popping open manhole covers.

“Just let it drain into their yard and into the storm drain, because it’s two completely separate systems,” Kahikina said.

A large tunnel is also under construction between two plants in Kaneohe and Kailua, which should also help fix the problem. That should be completed in June.

LocationStart/Stop TimesEst. Volume in Gallons
Ahuimanu Pretreatment Facility2 p.m. (2/18)/12:05 a.m. (2/19)2.18 million
Kaneohe Pretreatment Facility2 p.m. (2/18)/12:20 a.m. (2/19)6.5 million
45-1072 Grote Road2:36 p.m. / 3:05 p.m. (2/18)1,200
137 Popoia Road6:09 p.m. (2/18)/1:06 a.m. (2/19)63,765 (6,750 recovered)
431C Kawailoa Road5:35 p.m. (2/18)/ 1:06 a.m. (2/19)21,065 (21,065 recovered)
425C Kawailoa Road7:45 p.m. (2/18)/ 1:06 a.m. (2/19)14,565 (14,565 recovered)

The Ahuimanu Pretreatment Facility experiences an average daily sewer flow of 0.76 million gallons per day (mgd), but during the weekend storm received flows totaling 2.7 million gallons to 2.9 million gallons.

The Kaneohe Pretreatment Facility sees average daily sewer flows of 6.4 million gallons per day, but during the weekend storm received flows totaling 25.6 million gallons to 27.9 million gallons.

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