The Laguna Beach Planning Commission on Wednesday heard concerns from residents about a project to repair a deteriorating sewage tunnel in South Laguna and agreed to delay a vote on the issue.

Commissioners voted 4 to 0 — with Linda Dietrich absent — to continue the public hearing on the South Coast Water District's sewer tunnel stabilization and pipeline replacement project to Dec. 11, according to a meeting video on the city's website.

"This is a large project in scope and time frame, and it would be nice to have a full commission when we vote," Commissioner Ken Sadler said of the proposal, which calls for enlarging and stabilizing a two-mile-long existing tunnel that runs parallel to Coast Highway from Three Arch Bay north to Aliso Beach Park.

The district is seeking both conditional use and coastal development permits for the tunnel repair, which includes realigning 740 feet of the tunnel under bluffs at Three Arch Bay.

Residents near a proposed 15,000-square-foot construction staging area at Fourth Avenue and South Coast Highway are concerned about noise, dust and traffic that could result from vehicles going in and out of the district-owned property.

Carl Goodwin, who lives on Florence Avenue near the proposed staging area, represented several residents at Wednesday's meeting.

"We heartily support the project," Goodwin told planning commissioners. "Our interest is maintaining a reasonable quality of life for the life of the project."

Goodwin's concerns center on noise, including trucks' back-up "beeps," and dust. He asked if construction vehicles could stay off a portion of Virginia Way south of Third Avenue.

The project is expected to last five years and cost about $80 million, said Joe McDivitt, the district's interim general manager.

One million gallons of sewage travels through a pipeline each day within the two-mile-long tunnel, originally built in 1954, a district staff report said.

The tunnel, which is 6 feet wide by 6 feet high, runs parallel to Coast Highway and is primarily located beneath privately owned oceanfront properties from Three Arch Bay north to Aliso Beach Park, the report said.

The tunnel is deteriorating and repairs are needed to prevent it and the sewer pipe from failing, according to the report. It added that an upgrade would make working conditions for district employees and contractors safer.

L.C. "Bud" Smull, a resident of South La Senda Drive, supports the district adding to the proposed 500 feet of tunnel that will be directly under the street rather than the portion under the bluffs — for fear that a sewer pipeline rupture could hurt the ocean environment.

Smull hired Geofirm, a Laguna Beach-based engineering company with more than 30 years of work in Three Arch Bay, to evaluate the stability of the bluffs, according to a Sept. 4 letter from the company to the Planning Commission and the city's community development department.

"The proposed 500-foot portion will be 70 to 80 feet below the street, 150 feet inland from the beach and is undeniably more stable," Geofirm engineer Hannes Richter wrote in the letter.

Richter wrote that he supports the redesign but agrees with Smull that more of the line should be rerouted to run directly under South La Senda Drive rather than the bluffs. He said that would bring the line farther inland and make it less likely a sewage spill would reach the ocean.

Richter's concern pertains to the tunnel's portion along the bluff north until it reaches Bay Drive, he wrote.

"Significant bluff instability and land sliding has occurred historically along the cove below South La Senda and Bay Drive," Richter's letter said.

The water district said a tunnel directly underneath all of South La Senda Drive would be "impractical" and "unnecessary," according to an Oct. 22 letter to the Planning Commission and the community development department.

Smull's concerns have been vetted through a comprehensive public outreach process that included a February meeting with district officials, Smull, Richter and Three Arch Bay residents, the district letter said.