Sea Spill Linked to Air in Pipeline - Sewage: Preliminary report indicates buildup of trapped air led to rupture of San Diego’s sewage outfall line, bolstering belief that human error was at fault.

Preliminary findings by the firm investigating the cause of the city’s sewage outfall rupture indicate that a buildup of trapped air in the 29-year-old pipe triggered an explosion that, for two months, contaminated beaches here with billions of gallons of partly treated waste.

If that proves true, it would bolster the contention of some local sewage workers that human error created a giant bubble that burst the pipe. City officials have blamed “external forces,” such as heavy wave action, for the rupture.

The disclosure came Friday in the courtroom of U.S. District Judge Rudi M. Brewster, who also upbraided city officials for their recent flirtation with missing crucial deadlines in a consent decree that serves as a key component in a massive federal lawsuit.

Without taking definitive action, the San Diego City Council recently balked at the idea of doubling sewer rates over the next 11 years as a way of paying for several billion dollars’ worth of improvements in the region’s waste-disposal system.

Brewster expressed a willingness to be flexible on key elements in the consent decree, including an upgrading from advanced primary to secondary treatment of sewage at the city’s Point Loma facility and building as many as nine state-of-the-art water-reclamation plants.

Secondary treatment would remove 90% of the suspended solids, contrasted with the 75% to 80% now removed under the city’s advanced-primary system. The plant serves 1.7 million residents of San Diego County.

But Brewster was insistent that the city needs to spend money immediately--as much as $119 million in bonded indebtedness--to pay for a major overhaul of the sewage collection system, which he termed “decrepit.”

He then said that, unless the city takes immediate steps to rectify such problems, he would consider “reopening the penalty phase of the trial.”

The judge was skeptical of the city’s plans to spend $61 million on extending the recently repaired outfall and building an adjacent “parallel” pipe as insurance against the kind of catastrophe that marked one of the worst sewage spills in U.S. history.

The spill contaminated up to 20 miles of beaches from early February until early April, when the pipe was finally sealed. Before then, up to 180 million gallons a day of the treated waste had spewed into the ocean 3,150 feet offshore, at a depth of 35 feet.

Ordinarily, the effluent is discharged 2.2 miles offshore, at a depth of 220 feet. The proposed extension would deposit the plume more than 4 miles at sea, at a depth of more than 330 feet.

But the judge raised questions about the structural integrity of the extended outfall, saying that, if the old pipe failed to last even 30 years--much shorter than its purported life span--why would a longer version endure for 75, as engineers say it will?

It was in that context that city officials leaked fragments of the data being collected by the independent firm, Failure Analysis Associates of Menlo Park, Calif., which was hired to investigate the cause of the rupture as a condition of $10 million in federal and state money.

The Menlo Park firm investigated the explosion of the space shuttle Challenger and the collapse of the Hyatt Regency hotel walkway in Kansas City, Mo. Its report was due in mid-May but may not be fully available until mid-July, officials said Friday.

Dave Schlesinger, head of the city’s Clean Water Program, attempted to reassure the judge that none of the firm’s preliminary findings indicate that the city is making a mistake by going ahead with plans to extend the existing outfall.

Schlesinger said early results show the cause of the rupture to be “air entrainment,” or a heavy buildup of air pressure in the 9-foot-diameter pipe, that may have caused 35 of its 50-ton sections to rip apart.

He said investigators have ruled out seismic activity and corrosion in the pipe as causes of the spill, which closed beaches from the Mexican border to the San Diego River more than 20 miles north and led to a quarantine on fish and other marine life from the contaminated area.

Shortly after the rupture, a team of workers at thW. Blom Wastewater Treatment Plant told The Times that the simultaneous opening of a diversion gate and throttling valve created a “water hammer” that caused the pipe to fill with air and explode.

But Brewster said Friday that “terrible” inadequacies in the area’s sewage collection system overshadow any deficiencies in the Point Loma outfall pipe. The massive rupture was detected Feb. 2.

Before the waste reaches the Point Loma plant, where it undergoes advanced-primary treatment, facilities dispersed throughout the city collect it in its rawest and most toxic form.

The overflow of raw sewage from such intermediate centers has harmed San Diego neighborhoods and placed beaches in jeopardy for, at times, as long as a year, and the situation “must be corrected,” Brewster said, gesturing angrily.

On that point, the judge offered no flexibility.

“Hasn’t the court ordered the aggressive replacement of the existing (sewage-collection) infrastructure?” said Brewster, noting that the overflow of raw sewage in parts of the city is often “the source of all our problems.”

At another point, the judge said, “I read the newspaper. I watch television. I listen to the radio. And I’d have to be deaf, blind and stupid not to believe that the city hasn’t rescinded the consent decree.”

Chief Deputy City Atty. Ted Bromfield responded by saying that, on April 27, that the City Council raised “serious questions” about the direction the city was following in trying to comply with the federally mandated Clean Water Act.

The council “directed the city manager and the city attorney to investigate alternatives to the existing consent decree,” Bromfield said. Instructions were then given for the city manager to report back to the council Tuesday.

But, Bromfield said, the city failed to violate any decree, because no official action was taken, although timetables for financing upgrades to the city’s sewage-collection infrastructure are clearly in peril.

The council must act soon, Brewster said, or the consent decree will be violated.

“And, if the city is now abandoning aggressive work” on the sewage-collection infrastructure, which Brewster labeled his “highest priority,” the judge said he would “open up and revisit the penalty phase of the trial.”

Contrite city officials tried to reassure Brewster that their intention was not to challenge his authority. City Councilmen Tom Behr and George Stevens pleaded with Brewster to understand their broader fiscal concerns, such as the burden on ratepayers.

“We have not attempted to rescind the consent decree,” Behr said. “And, in my mind, the (municipal sewage collection system) has to be upgraded, and I believe we will go ahead and authorize that (on Tuesday) or shortly thereafter. I can say on behalf of the city I think it will happen.

“In none of our discussions have we said, ‘The municipal system should not be done.’ I can’t control what the other members do, but I will take your very clear message back and suggest we get on with it.”

Brewster said that, at times, he was “not satisfied that the consent decree is in the public interest,” but an upgrading of the collection system, en route to the outfall pipe, is so important that it overwhelms consideration of any improvement at the treatment plant.

The judge ordered all parties to appear at the next hearing July 10.