L.A. Studies Plan for 2nd Sewer Pipe to Ocean

The City of Los Angeles is considering building a second ocean outfall for its giant Hyperion sewage plant, and one of the three routes being studied slices south into waters off Redondo Beach.

The proposal for another tunnel-sized outfall, which would be from three to five miles long, is in its early planning stages. The city’s Department of Public Works has yet to receive approval for the estimated $170-million to $200-million project from permitting agencies or the Los Angeles City Council. An environmental impact report will not be ready for public review until March, 1991, at the earliest, officials said.

Still, the prospect of 350 million gallons of effluent per day entering South Bay waters is already stirring local opposition.

“I’m very concerned,” said Torrance City Councilman Dan Walker, who sits on a state water panel that would have to review the outfall proposal. “We have the best of a bad water quality situation in Santa Monica Bay, and now they want to give us this.”

Richard Bonham of the South Bay Boaters Assn., a grouping of King Harbor boaters, said, “We’ve got to be very vigilant,” and if the plan goes ahead “we have to fight it tooth and nail.”

Los Angeles officials said they are considering a new outfall because the principal one in use cannot handle all the plant’s effluent by force of gravity alone, requiring the plant to use costly electric pumps.

These large pumps push the treated sewage through that outfall--a 12-foot-diameter line that extends five miles almost due west from Hyperion--when the flow from Hyperion exceeds a rate of 325 million gallons a day. Plant Manager John Crosse said the pumps are in use 16 to 17 hours a day, running up electric bills of $100,000 a month.

Another problem, officials said, is that occasional power outages idle the pumps, and excess effluent is sent through an emergency outfall that discharges just one mile offshore.

Sanitation officials argued that with Hyperion’s sewage flows growing year by year, power failures could hold increasingly serious consequences--especially during wet weather, when rainwater seeps into the system and sewage flows are at their height.

“We could be receiving a billion gallons a day during wet weather after the year 2000,” Crosse said. “With only the five-mile outfall, the one-mile outfall and no pumps, there’s a potential we wouldn’t be able to get the (sewage) out of the plant. We’d flood the plant.”

Crosse said Hyperion handles an average flow of 365 million gallons daily, with flows during the 11 a.m. to 11 p.m. peak hours reaching a rate of 500 million gallons a day. In wet weather peak flows have approached 700 million gallons per day, he said.

City officials and a private consulting company are studying three main routes for a new outfall. One would run alongside the current five-mile line, another would extend slightly to the north and the third would be angled southward, toward the underwater Redondo Canyon off Redondo Beach.

Each route includes options for three-, four- or five-mile outfall lengths that end in two branches, called diffusers, of several possible sizes. City sanitation officials said they are considering 18 outfall variations in all.

Walter Naydo, the chief of construction at Hyperion, said the goal is to wind up with a reinforced concrete pipeline that is 12 to 13 feet in diameter and capable of handling a gravity flow of up to 350 million gallons of effluent daily. The price, he said, would be $170 million to $200 million.

Naydo declined to say which of the three routes is preferred for the outfall, but he said there are two engineering arguments against the southern option and one in favor of it.

Unlike the comparatively smoother routes to the north, the southerly path crosses rocky terrain that would be more difficult to build on. It also enters a portion of the Palos Verdes Hills fault zone, making it more vulnerable to earthquakes.

The route’s chief benefit, however, is that the sea floor drops off more sharply in the direction of the Redondo Canyon than it does along the other routes. According to Naydo, that means the line doesn’t have to be as long to reach the depths at which effluent disperses.