Plant Workers Cite Human Error in Spill : Sewage: They say improper maneuvers created an air bubble that shook the pipe ‘like a garden hose.’ The city disputes that, but orders an investigation.

An in-house diversion of sewage rocked the city’s waste water treatment plant and created a large air bubble that caused the building to shake violently, two days before the U.S. Coast Guard discovered the massive spill off the coast of Point Loma, according to plant employees.

Five workers said the combination of opening a diversion gate and a throttling valve trapped air in the huge outfall pipe, causing it to “shake like a garden hose,” in the words of one employee, and creating what a plant operator called a “water hammer.”

City Manager Jack McGrory, who maintains that the spill was caused by natural forces, nevertheless ordered a full investigation into the matter late Thursday.

Experts said a water hammer could have triggered the rupture in the pipe, which continues to spew 180 million gallons a day of partially treated sewage into the ocean 3,150 feet off Point Loma, at a depth of 35 feet.

Claude Janowicz, a nine-year operator at the treatment plant, said employees believe the rupture occurred about 11:30 a.m. Jan. 31, when workers opened a diversion gate and a throttling valve at the same time, creating a massive air bubble in the outfall line.

“It would cause the pipe to lift, jerk it back and forth. . . . It’s human error--it’s as obvious as hell,” Janowicz said. “A lot of us here are concerned because we’re talking about public health, and as employees, public health has to be--or rather, ought to be--our primary concern.”

The four other workers, who asked not to be quoted by name, backed up claims by Janowicz that the diversion of sewage was botched, and said they were at the plant when it shook violently.

But city engineers vigorously disputed claims by workers that an internal force could have triggered the break, discovered the night of Feb. 2. Miles of coastline have been quarantined for most of the month because of dangerously high counts of fecal coliform bacteria.

Nothing unusual happened at the plant at 11:30 a.m. that Friday, the city said. At 2 p.m. that day, however, supervisors ran effluent through the newly repaired throttling valve for the first time in months, officials said.

In about 10 minutes, millions of gallons of effluent went rumbling through the valve, which shook the plant somewhat, said Stan Fein, senior maintenance supervisor for the plant, who said he opened the valve.

“There was nothing unusual about it,” Fein said. “We brought the valve on line in the usual manner, nothing significant or out of the ordinary.”

Most often, the effluent runs through another pipeline, which also needed to be repaired. Fein said it is rare that the treated sewage is diverted from one system to another, a procedure that had not occurred for several months.

Plant workers may have confused the two incidents, city officials said Thursday. But the employees were equally adamant about the time and circumstances of the diversion.

A number of city officials, including Fein, Deputy City Manager Roger Frauenfelder and Milon Mills, the city’s water utilities director, say it is impossible for a water hammer to occur within the present-day treatment system.

“A water hammer happens when you have a gate that is suddenly closed and the inertia of the water hammers into wherever it was stopped,” Frauenfelder said. “We have no gates here to slam shut. The system is open on both sides. In my opinion, as a professional engineer, it couldn’t happen.”

But experts say a bubble of such force is capable of damaging the pipe, each section of which is 25 feet long and weighs 30 tons. Repairs to the outfall pipe are estimated at $10 million.

A water hammer, or “upsurge” in the system, “cannot be ruled out as a cause of the break, but in the list of things that contributed to it, we think it’s very unlikely,” said Greg McBain, an executive with Engineering Science, the firm hired by the city to investigate the cause of the rupture.

McBain said he believes the rupture was caused by shifting sea currents and settlement of the ocean floor, a theory the city strongly supports. Mayor Maureen O’Connor has even termed the break a “natural disaster.”

Ladin Delaney, who for nine years was executive officer of the state Regional Water Quality Control Board, said he had worried about the possibility of a water hammer damaging the line.

He defined a water hammer by saying: “It’s like when you turn the water off quickly in your house and you hear a loud bang. It’s the same principle. But extremely large forces are developed by having a water hammer in the city’s outfall pipe.”

Delaney said the creation of a water hammer was one of his main concerns about the E. W. Blom Wastewater Treatment Plant and one he relayed repeatedly to city officials, after such an occurrence several years ago during an inspection by the water quality board.

“It sounds completely logical to me,” said Delaney, a consultant who recently retired from the board. “I was concerned about a water hammer in the outfall before. I don’t know that that’s what happened this time, but based on past concerns, it’s highly plausible.”

Delaney said he based his concern on firsthand observations by one of his inspectors, who was touring the Point Loma facility several years ago when a water hammer blew a large cover off the top of the outfall pipe.

That inspector, David Barker, now a senior official with the water quality board, said the incident occurred in the 1970s, when a “butterfly” valve “not operating properly created a back flow,” in which effluent gushed over the cliffs near the shore.

“One of the big things we always worried about with the plant was ‘air entrainment’--air getting sucked into the pipe,” Delaney said. “We were concerned for two reasons. (Air entrainment) cuts down on the hydraulic capacity of the line, and, of course, it creates a water hammer, which was our biggest concern.”

City Manager McGrory said he was aware of a water hammer incident that occurred in 1986. As a result, the city built a pipe to bleed air from the system and is now designing a separate set of pipes that will draw air out of the outfall completely.

Over the years, various inspections have turned up evidence of corrosion in the outfall, caused mostly by the presence of air in the system, city officials said.

At the time of the most recent incident, workers at the plant said, most personnel were in a separate part of the building, having a “pizza party” for a friend.

One plant employee said that electricians working on a throttling valve asked a supervisor to open the diversion gate, through which at least 150,000 gallons of effluent passes every minute.

Sources said the gate was opened quickly, not slowly as it should have been, allowing a rapid buildup of pressure. That, followed by the quick opening and closing of a throttling valve, created the water hammer, according to plant operator Janowicz.

“They should have never opened the gate that quickly,” he said. “But this story the city’s putting out--that ‘natural forces’ caused it, well, we all think that’s pretty funny.”

McGrory and other officials say it is impossible to open the gate in fewer than six minutes because it is hydraulically controlled. At that rate, engineers say, the flow of effluent is moderate and could not cause a problem.

In this case, the gate was opened in 10 minutes, according to Fein, the supervisor on the job at the time.

A maintenance worker at the plant, who asked not to be identified, said: “What happened was, they were exercising the throttling valve at high flow and got air trapped in the valve. It’s all real hush-hush out here, and no one really wants to talk about it.”

Delaney, the former water board official, said he “had conversations with city staff about this on a number of occasions” and even wrote a letter in 1989 to Frauenfelder detailing his concerns about the amount of air in the sewage pipe.

“In the letter, I asked them to give me a chronology of any event, or problem, with the outfall, and when I got it, I saw no evidence of a water hammer problem, which we knew existed out there, because we had seen it,” Delaney said. “So I asked Frauenfelder about it, and he professed to have no knowledge about it.”

Delaney said he was also concerned about corrosion in the joints of the outfall pipe, which was built in 1963 and which, according to city officials, had performed without incident until recently.

Normally, the outfall pipe discharges the sewage--from which 75% to 80% of the solids have been removed--2.2 miles out to sea, at a depth of 220 feet. Delaney said his concerns about the pipe “go back years.”

“My concerns about the potential for water-hammer damage, plus concerns about corrosion . . . well, those two things together was why I questioned the structural integrity of the entire system,” he said.

Another top state inspector, who asked not to be quoted by name, said late Thursday: “Forces that develop from water hammers can disrupt pipelines or cause pipelines to fail. That could have happened in this case.”

But McBain, the city’s hired inspector, said the diversion gate must be opened in order for the throttling valve to work and that the operation of both at the same time is normal procedure.

The cause of the rupture, city officials say, won’t be fully determined until they are well into the repair process, which has been delayed by bad weather. The 100--by-300-foot barge that will lift up the 500 feet of damaged sections of pipe resumed work Thursday.