The city has begun preliminary work on a new sewer line serving Waikiki that in two years will replace the above-ground, temporary pipe running along Ala Moana Boulevard.

The black above-ground pipe has been a visible reminder of the March 2006 break in which an aging sewer force main ruptured, sending 48 million gallons of raw sewage into the Ala Wai Canal. It was the worst sewage spill in state history.

The new sewer main, 5,800 feet long and 6 feet in diameter, will run from Ala Wai Elementary School to the eastern entrance of Ala Moana Beach Park. It will connect to the Beachwalk Wastewater Emergency Bypass — completed last year — that goes under the canal to its mauka bank.

When the $37 million project is completed in 2012, the city will have two lines serving the area, the new pipe and the original rehabilitated pipe. Should problems arise with one line, the city will be able to switch to the other line.

While traffic disruptions are expected, Rick Egged, president of the Waikiki Improvement Association, said the project is necessary and vital.

"Certainly this project is very important not only to Waikiki but the surrounding community as well," Egged said.

Micro-tunneling work to install the pipe underground is scheduled to begin next month. Micro-tunneling is a less-disruptive process in which a boring machine is used to burrow a tunnel, avoiding the need for an open trench. Access points called "jacking pits" are dug at intervals so 20-foot pipe segments can be lowered into the tunnel 40 feet below the surface.

Contractor Frank Coluccio Construction Co. will use "silent pilers" to push the pipes into the ground, instead of driving them, reducing noise.

The new pipes are made of fiberglass and are corrosive-resistant to withstand sewage gases, president Franco Coluccio said.

A challenging part of the project will be under the McCully Street/ Kalakaua Avenue area, where the tunnel will be on a curve. Micro-tunneling is normally done in a straight line. At the curve, contractors will use 5-foot-long pipe sections and a high-tech navigation system.

"It’s a more tedious process," Coluccio said, adding that it is the first project in the United States to include a curved micro-tunneling alignment.

Contractors will work 10-hour days, Monday through Saturday.