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Corrosion Report Predated Sewer Collapse

Tuesday, November 14, 2017

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Officials in Sterling Heights, Michigan, said last week that their county disregarded corrosion-related warnings that presaged a destructive sewer collapse last December.

The Detroit News reported Thursday (Nov. 9) that Sterling Heights accused Macomb County Public Works of ignoring engineers’ reports stretching back to 2013, failing to address corrosion in the sewers that they say ultimately led to the catastrophe. The city has long held that the county, and not ratepayers, should be held responsible for the cost of the recovery effort.

Sewer collapse site
Images: Macomb County

The sewer collapse occurred Dec. 24, 2016, and resulted in a 100-foot-by-300-foot sinkhole.

The sewer collapse, which began Dec. 24, 2016, occurred on the border of Sterling Heights, Clinton Township and Fraser, north of Detroit. The Macomb Interceptor sewer collapsed along 15 Mile Road, creating a sinkhole 100 feet wide and 300 feet long.

According to the News, the disaster forced residents to evacuate 22 homes, and resulted in the demolition of two. The total cost of repairs has already topped $70 million; the county has expressed that it would like to go ahead with a second phase of repairs, which would create a permanent fix and make the final bill $150 million.

Corrosion Concerns Aired

The newspaper released the 2013 report, from engineering firm Giffels Webster, which said on its first page that a prior study, in 2006, had identified corrosion issues, and the county (and the line’s previous owner, the City of Detroit) had seemingly taken little action to remedy the problems. “It was estimated that 0.18 to 0.29 inches of sewer wall was being eaten away per year,” and that without a fix, “corrosion could result in hundreds of millions of dollars in costly repairs to the sewer infrastructure as well as potentially leading to catastrophic collapse.”

Before and after

The Macomb Interceptor, which collapsed in December, experienced similar collapses nearby in 1978 and again in 2004.

The more recent report noted that conclusions in the 2006 study were “antiquated and unreliable” based on the amount of H2S in the sewers. The corrosion problems likely became more widespread and severe in the ensuing years, the engineering firm said.

A separate 2010 assessment, the report says, found that based on hydrogen sulfide corrosion, the pipeline—built in 1973—would lose between 1.83 and 7.64 inches over 100 years of service.

According to Macomb County Public Works, in 1978, a similar collapse occurred about 1,000 feet west of the 2016 incident. In 2004, another collapse occurred about 1,000 feet west of that.

Repair Cost Battle

The county sold $70 million in bonds to finance the repairs, in addition to a $5 million state grant. It says the ultimate cost will be borne largely by customers of the Macomb Interceptor Drain Drainage District, which comprises 11 municipalities.

The county has said that ratepayers will see an increase of 8 to 9 percent over the next 25 years—up to $60 per year per home.

Map of sewer collapse

The collapse happened in Fraser, Michigan, near the border with Sterling Heights and Clinton Township.

Sterling Heights sued Macomb County earlier this year, arguing that former Public Works Commissioner Anthony Marrocco had known about the issues with the sewer line for years and did not address them. The suit was thrown out in May.

Shortly after, it was revealed that Marrocco was under investigation by the FBI, a fact that Sterling Heights officials said bolstered their argument that he and his department were engaged in wrongdoing related to the sewer line.

The city’s suit against the county continued under appeal, and Marrocco was added as a defendant in July.


Tagged categories: Corrosion; Microbiologically Induced Corrosion (MIC); NA; North America; Pipes; Quality Control; Sewer systems

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