Debate Over Tunnel or Trench Stalls Sewer Project

A lengthy reconsideration of which construction method to use in replacing one of Los Angeles’ oldest, most rapidly decaying sewers has significantly delayed the project, increasing the likelihood of partial street collapses and unpleasant odors along the sewer’s path from downtown to the Baldwin Hills.

Rapid decay in the 11-mile sewer line already has led to cracks, overflows, at least four sinkholes and about a dozen cases of putrid smells escaping above ground, city engineers and residents say.

Despite the urgency of replacing the 1920s-era line, documented by remote-control videotape cameras that showed the amount of badly damaged pipe doubling from 1993 to 1996, a $240-million replacement project has been stalled for 1 1/2 years as officials rethink their decision to lay new pipe in a tunnel.

According to documents in city files, engineers years ago settled on tunneling, rejecting the cheaper, faster alternative of putting the new pipe in an open trench and then covering it with soil as less technically desirable and too disruptive for the neighborhoods through which the line runs. Engineers say trenches would be open on a given block for two to three months.

But in spring 1996, after public hearings had been held and the city’s Board of Public Works had approved a $900,000 environmental impact report on tunneling, city engineers went back to the drawing board to reconsider digging trenches.

They said price had become a more important consideration since the project was conceived in 1985 as part of a general revamping of waste water treatment to bring Los Angeles into compliance with the federal Clean Water Act. This project, on what is known as the East Central Interceptor Sewer, is the last piece of that revamping.

City Engineer Sam Furuta said that although using trenches is likely to be more disruptive than tunneling, it also has advantages--in saving money and construction time--that the City Council should consider in making a final decision.

Although it will probably take another year, and another $500,000, just to study the environmental impact of the trench method, officials say that if it is adopted, it could shave 1 1/2 years off the project’s four-year construction phase and cut $60 million off the project’s estimated price.

Ultimately, the City Council will decide which technique to use in part by answering the question: How much inconvenience is $60 million worth?

“We’ve spent a year trying to make this changeover,” Furuta said. “I thought . . . the City Council . . . should have the option of choosing tunneling or open trench.”

When the trench alternative was first unveiled last spring, it came as a surprise to the council member whose district is most affected by the project and who has been one of its biggest backers.

Councilman Mark Ridley-Thomas said he believes a replacement sewer is necessary for public safety and health reasons. Because a new sewer will also enable engineers to take the existing one out of service and repair it, the replacement project would also provide the additional infrastructure for increased economic development in the area, he said.

But Ridley-Thomas was upset because city engineers had told him repeatedly that tunneling was the only option. “What have we been doing all this time trying to get people [in the affected area] comfortable with tunneling?” he asked.

Attributing the misinformation to management deficiencies in the Department of Public Works, he flexed his political muscle, persuading the council in June to overrule a Public Works Commission decision to authorize more money for an environmental impact evaluation of digging trenches.

He demanded project management changes in the Bureau of Engineering before he would let the money go through. He is getting those changes, along with a plan for educating people who live near the sewer about engineers’ perceived need for a replacement.

Saying he has no opinion yet on whether tunneling or digging trenches would be better, he indicated in an interview that he may allow the funding decision to come to a council vote as early as next month.

“This train needed to be halted for the purpose of making sure it was headed the right way and had the right conductor,” Ridley-Thomas said. “It’s too important to be unclear about whether or not we were doing the right thing in the right way.”

During the first environmental study, prospects of tunneling had stirred community anger in the wealthiest, most vote-rich part of Ridley-Thomas’ district, near the Baldwin Hills. Some residents expressed concern about repeating Hollywood’s experiences with a giant sinkhole and the widespread settling of buildings along the path of the Metropolitan Transportation Agency’s Red Line subway.

Proposed tunnel shaft sites were also controversial. One would require condemnation of several homes; another would be next to an elementary school.

And there were charges that city engineers wanted to build a new line only to increase sewage storage capacity under largely African American neighborhoods--capacity they would then use to meter the flow of sewage to the Hyperion Sewage Treatment Plant.

Noting that excrement from much of the San Fernando Valley passes through the line on its way to Hyperion, retired engineer and Baldwin Hills resident Milton Bassett declared: “They want to make this a cesspool for the Valley. . . . It is racist.”

Bassett has proposed that the city build another waste water reclamation plant instead. It could provide for additional sewage storage and thus ease the flow in the sewer through his neighborhood.

City Councilman Nate Holden, whose district is also affected, has endorsed that idea.

But in a May 1996 letter to Holden, then City Engineer Robert Horii said a new reclamation plant, which would take 15 years to build, would still not allow the city to make needed structural repairs to the existing, decaying sewer line.

Horii said there was no time for delay. “Unfortunately the [sewer, one of five main lines that feeds Hyperion,] is deteriorating structurally at an accelerated rate, endangering the general public in terms of potential sewer collapses,” Horii wrote.

Holden remains steadfast in questioning the need for the project. He said last week that, as he understands it, all necessary repairs to the sewer have already been made and that “my people are not willing to have the neighborhood torn up.”

City engineers say Holden is incorrect about the extent of repairs. They say repairs to part of the line have been underway for some time, with workers slipping new pipe inside the old. But engineers say that most of the decaying sewer cannot be repaired this way, that it must be fixed by hand--a process that requires virtually shutting the sewer down.

Because the sewer often operates at capacity, engineers say another line needs to be in place to carry the flow before they can close the old one.

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An Inside Look

Walls: Built in the 1920s, the walls are thought to have been 10 inches thick at the crown.

Tiles: Clay tiles have held up well, but the mortar used to attach them has not.

Consequences: As tiles have fallen off, concrete has started to corrode, increasing danger of collapses.

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Sewer Slowdown

An 11-mile section of one of Los Angeles’ oldest sewers, known as the North Outfall, is rapidly decaying. But disagreements over the best method to use in replacing it have significantly delayed the project.