Metal Cleanup Leads to an Ironic Corrosion in Sewers

Los Angeles County sanitation officials say their success in stemming the tide of toxic metal pollution has caused a sewer pipe corrosion problem that will cost $135 million and take five years to correct.

If adopted, the corrosion repair program could almost double sewer fees in the service area, officials say.

Ironically, accelerated corrosion of the concrete sewers is the result of progress made in reducing the dumping of toxic metallic wastes into the sewage system.

The metals combine chemically with organic sulfur and prevent the formation of caustic sulfuric acid. Removal of the metals resulted in a dramatic increase in sulfuric acid. Corrosion is occurring so rapidly that some pipes, which were supposed to last 100 years more, now are expected to require replacing within five years.

As a stopgap measure, officials have been spending $3 million a year to put nontoxic metals such as iron, as well as hydrogen peroxide, into sewage lines in an effort to limit the acid attack.

In a longer-range approach, officials have proposed the $135-million repair job.

“The sewers have to be repaired immediately,” Charles W. Carry, chief engineer and general manager of the County Sanitation Districts of Los Angeles County, said Wednesday.

In some cases the corrosion was so bad that the county sewage agency, which serves about 4 million residents of 77 cities in 760 square miles, could not afford to wait.

The concrete roof of one large sewage tunnel under the Long Beach Freeway in Long Beach became so pitted that officials feared a collapse. A photograph of the tunnel shows corroded steel reinforcing bars protruding from concrete.

“That is the one that worried me the most,” said John Redner, sewage system superintendent. “We had to jack a new pipe under the freeway and fill that one up with concrete.” The concrete of the new tunnel, completed last summer, is coated with a plastic that resists corrosion.

In a more recent case, officials dug up a 20-year-old pipe designed to last 100 years near the intersection of Figueroa Street and Sepulveda Boulevard in Carson.

They found that concrete originally 6 inches thick had corroded to less than half that thickness. They never found the reinforcing rods. All that were left were rib-like indentations in concrete. Officials replaced the worst sections and jammed 1,000 feet of plastic liners up the line to protect still-serviceable parts of the line.

Approval of the program proposed by sewer system officials will ultimately mean an increase in sewage fees to about $50 per year for a single-family home, officials said.

This year, fees--now between $27 and $31 a year--are to be increased to $37 to $43 a year under proposals now going before the local boards that govern the system. Carry described the fee increases for this year as the largest in the history of the sewage agency.

Last year, for example, in District 5--an area that includes Culver City, El Segundo, Gardena, Hawthorne, Inglewood, Lawndale, Lomita, parts of Los Angeles, Manhattan Beach, Palos Verdes Estates, Rancho Palos Verdes, Redondo Beach, Rolling Hills, Rolling Hills Estates, Torrance--the annual sewage service fee was $21 a year ago, now is $27 and will rise to $40 if the District 5 Board approves the increase next month after a public hearing.

Almost all of the proposed increase, which would become effective July 1, is budgeted to pay for replacing corroded pipe.

Even with the increase, sewage service in the areas served by the county sewer agency will be less expensive than in the city of Los Angeles, where fees range from $60 to $120 per dwelling unit, Carry said.

County sewage officials learned how serious the sulfide corrosion problem had become after completing a study two years ago of the condition of the pipes.

“It is ironic,” said Joseph Haworth, a spokesman for the sewage agency. “You are (removing) the metals to prevent ocean dumping and you get the corrosion.

“Nature has its ways. That will teach you to fool with Mother Nature.”

But to local officials attending district board meetings Wednesday, the corrosion was an unpleasant surprise.

“You never realize these things are going on when you are flushing,” said Betty Ainsworth, mayor of Hawthorne.