The flow of raw sewage into the Ala Wai Canal has been stemmed, but not before 48 million gallons of untreated wastewater were dumped and contaminated Waikiki Beach.

Officials don't expect beach contamination to dissipate soon and people may be warned to stay out of the water for as long as several months.

"There's no real estimation," said Kurt Tsue, state Department of Health spokesman. "It could be anywhere from weeks to months."

Bacteria levels were dropping but still high yesterday at surf spots and Waikiki beaches so the department left up signs that warn people to stay out of the water.

City crews yesterday learned that their repairs held tight, containing the waste from a main that ruptured on Friday. Untreated sewage from that pipe was being pumped into the Ala Wai Canal as the city tried to repair it.

The fix included a wrap of lead wool and fiberglass, followed by steel-reinforced concrete that was poured around the line, which is about 10 feet below street level.

Repairs to the line were completed Tuesday and the line was back in partial use beginning Wednesday afternoon.

Following the rupture, the city began testing the waters and the state ordered warning signs to be posted when bacteria levels reached unacceptable levels.

Many factors contribute to the reduction of bacteria including rain, which dilutes bacteria, and sunshine, which kills it, Tsue said.

Wind and tide could also help reduce the bacteria, he said.

At a news conference, Mayor Mufi Hannemann stressed yesterday that the public and tourists should heed the warning signs and wait for the state Department of Health to give the all-clear signal.

However, bacteria levels are dropping and Hannemann said no more beaches will be closed.

"I want to acknowledge the fact that it's not over for Kai'olu Street," where the main is located, he said.

He also said that during the repairs, workers discovered a leak in a water supply line. The leak must be repaired before the road is paved, he said.

The full cost of the emergency project won't be known until all the invoices are submitted and calculated, said Wayne Hashiro, city managing director. Experts had to be called in, contractors hired and equipment provided on a moment's notice, he said.

"We requested $3 million in contingency funds," Hashiro said. "But until we get the final numbers, all the invoices, we wouldn't be able to tell you."

He said he didn't know what caused the break. Speculation about pile driving at a nearby construction project arose, but an investigation by experts is needed, he said.

The city had planned to replace the ruptured main and then use it as a backup, he said. A contract could be awarded by the end of the year, Hashiro said.

Hannemann said the city is in the process of repairing or replacing its 1,500 miles of sewer lines. In the past two years, 150 miles of work has been completed, he said. Some 55 percent of the capital improvement projects in the city budget is for sewers, Hannemann said.

"We take our responsibility with wastewater very seriously and we have a plan to not only maintain and catch up with the maintenance problems of the past but to put this city on a better footing," Hannemann said.

Reach Eloise Aguiar at eaguiar@honoluluadvertiser.com.