Honolulu's aging sewer system withstood Sunday's earthquakes without significant damage, according to city officials.

"I don't know of anything in terms of problems related to the sewer lines," said Craig Nishimura, deputy director of the city Department of Design and Construction. "The whole system seems to have withstood that jolt."

Some partially treated wastewater was released from three treatment plants — Kailua, Sand Island and Wahiawa — but that was because of the power loss during Sunday's blackout, not because of the quakes.

Nishimura said officials found no evidence of collapse and received no trouble calls that would have signaled bigger problems.

City crews constantly inspect sewer lines with tiny video cameras that look inside the pipes. By taking video, the city can see cave-ins, root growth, and when there is a break in a line caused by an earthquake.

Nishimura suspected that there would have been more damage if O'ahu experienced the same jolt as the Big Island. But much of the Big Island doesn't connect to a central sewer system, so it has fewer miles of pipe.

"If they had more infrastructure, they probably would have suffered damage," he said.

More flexible technology also helped O'ahu. He said engineers design pipes to withstand some movement by building in joints that help absorb shaking.

Pipes also are built with cushions around them, he said, and PVC and other plastic pipes have more flexibility than older pipes.

Under pressure from a 1995 federal court consent decree, the city has poured hundreds of millions of dollars into improving the city's aging sewer system. Over the course of the 20-year decree, the city expects to spend close to $2 billion. Some spending increases have come in election years.

Nishimura said progress has been made. "A lot of the lines that were identified as in danger of collapse, those have been fixed," he said.

Reach Robbie Dingeman at rdingeman@honoluluadvertiser.com.