Workers Link Air Bubble to Sewage Spill

Workers at the city’s waste water treatment plant said Thursday that a diversion of sewage within the facility created a large air bubble that caused the building to shake violently two days before the Coast Guard discovered a massive spill off the coast of Point Loma.

Five employees said the combination of opening a diversion gate and the use of a valve that had not been opened for several months trapped air in the huge outfall pipe on the morning of Jan. 31, causing it to “shake like a garden hose,” in the words of one worker, and create 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 from the shores of Point Loma at a depth of 35 feet.

Claude Janowicz, a nine-year operator at the 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.”

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.”

But city engineers vigorously disputed charges 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.

City officials said the plant did not shake on the morning of the Jan. 31. At 2 p.m., they said, supervisors ran effluent through a valve for the first time in months after it had been repaired.

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

“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.”

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 water hammer happens when you have a gate that is suddenly closed and the inertia of the water hammers into wherever it was stopped,” Deputy City Manager Roger Fraunfelder 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 Janowicz, one of the plant operators, said the combination of having a diversion gate and throttling valve open at the same time “would cause all that liquid to take air right through the line. It would make it extremely buoyant. It would be like having air in a submarine.”

Ladin Delaney, who for nine years was executive officer of the Regional Water Quality Control Board, said Thursday that the creation of a water hammer was one of his main concerns about the E.W. Blom Wastewater Treatment Plant and one he had relayed repeatedly to city officials after such an occurrence several years ago.

“It sounds completely logical to me,” said Delaney, a consultant who recently retired from the regional 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.”

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 designing a separate set of pipes that will draw air out of the outfall completely.

Environmentalists have called the break in the outfall pipe an ecological catastrophe, equating it with the Exxon Valdez oil spill because of its lasting impact on marine life and kelp beds less than three-quarters of a mile from the cliffs of the Point Loma Peninsula.

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