TEPPFA - Reference Project in Utilities

The sewer system of Honolulu escaped unscathed after a major earthquake hit Hawaii. While other pipes are built with cushions around them, PVC and other types of plastic pipes were flexible enough to withstand the intense shaking on their own.

Early Sunday on 15 October 2006 a strong earthquake shook Hawaii, jolting residents out of bed and causing a landslide that blocked a major highway. Ceilings crashed at a hospital and aftershocks kept the state on edge.

A disaster declaration was issued for the entire state announcing that there had been damage to buildings and roads. Luckily there were no fatalities from the earthquake that had been measured at 6.7 on the Richter scale.

While electricity and traffic lights went out, Honolulu's sewer system withstood the earthquakes without significant damage. That according to a city official.

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

Flexibility is the key

On the island of O'ahu a more flexible technology helped the sewage system withstand the quake. The plastic pipes simply came with the flexibility. But the engineers had to build cushions around the traditional pipes to help absorb shaking.

"Pipes are built with cushions around them, and PVC and other plastic pipes have more flexibility than older pipes," Craig Nishimura told the Honolulu Advertiser.

The city constantly inspects sewer lines with miniature video cameras that scan the inside of pipes. The video will reveal cave-ins, root growth and most relevant in this case a break in a line caused by an earthquake. The video discovered no evidence of collapse within the system. Furthermore, city officials received no calls from citizens that would have indicated that they had bigger problems.

20 years of renewal

Under pressure from a 1995 Federal Court consent decree, the city poured hundreds of millions of dollars into improving the aging sewer system. Over the course of the 20-year decree, the city expects to spend close to $2 billion.

"A lot of the lines were identified as in danger of collapse. Those have been fixed," Craig Nishimura noted.

Much progress has been made and certainly enough to withstand many shocks on the scale of Richter.

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