The major sewer line, which serves nearly half of urban Honolulu, ruptured yesterday at Sand Island, sending thousands of gallons of raw sewage into the harbor.

Frank Doyle, city Environmental Services director, said overnight vacuuming by pump trucks with capacities of 2,000 to 6,000 gallons have ensured that "nothing’s going into the ocean." Doyle said the sewage is going into a pit.

Officials plan to look at the break in the 66-inch main later today after excavation and de-watering work at the site is completed, said Doyle.

Noting that a secondary 55-inch main was able to handle peak loads between 8-9 p.m. yesterday and 10 a.m. today, Doyle said repair work on the damaged main can proceed if the weather holds up. A 10-inch bypass line where the 66-inch main is damaged was being installed as a contingency for bad weather, Doyle said.

"Containment was our biggest problem," Doyle said. "Now we can dig down and see (what the damage to the main is). The key now is the weather."

Doyle said the rupture of the 66-inch main is the largest pipe break the city has ever had.

The break was detected at about 9 a.m. yesterday when crews at the Sand Island state park discovered a marshy area near the mouth to the harbor as pressure at the treatment plant began to drop. Doyle said last night that he did not know how much raw sewage spilled on land and how much went into the ocean.

"Our main priority now is to contain what we have as much as we can," Doyle said. "Our priority is the ocean. We want to keep as much from going in as we possibly can."

Doyle said he did not know what caused the pipe to rupture, but he said it may be related to a "transition point" where the 66-inch main under the harbor connects with a 78-inch main on land.

By 11:15 a.m. yesterday, sewage was diverted from the 66-inch main to an older 52-inch main that also runs under the harbor. Both lines connect the treatment plant with the Ala Moana pump station, which serves an area ranging from Sand Island to East Honolulu, excluding Hawai'i Kai.

Doyle said the broken pipe is about 22 years old, while the 52-inch main that is doing the work for two pipes is about 50 years old. Although the large pipe was shut down, residual sewage continued to leak out of the ground throughout the day.

A temporary 10-inch pipe was to be installed overnight to help with the peak-flow periods, Doyle said. The repair is being done by city crews and private contractor Hawaiian Dredging.

Doyle said he didn’t know how much it will cost to repair the break.

"It’s not something we can fool around with. We gotta get it taken care of and get it done and that’s what we’re going to do," Doyle said.

The Sand Island treatment plant processes about 70 million gallons a day. During storms or heavy rains, wastewater flow to the plant can reach between 170 million and 200 million gallons a day, Doyle said.

He said he didn’t believe yesterday’s spill was related to the recent storms.

The heavy rains have caused problems with the island’s sewage treatment system, particularly on the Windward side where nearly a quarter-million gallons of sewage spilled onto roadways and into the ocean last week.