Tuesday, February 11, 2014

The Cat Strikes Again: PCBs in a North Carolina Wastewater Treatment Plant

As we’ve noted before, Polychlorinated biphenyls (PCBs) are a bit like the pink stain in the classic children’s book The Cat in the Hat Comes Back. Once introduced into the environment, they have a knack for both persisting and resisting efforts to be removed effectively and efficiently, and with a little “help” - in this case, criminal activity - can contaminate everything from sewers to sediments to wastewater treatment plants.

Unfortunately PCBs have been getting a little more “help” than usual lately: First in South Carolina, and now – in an incident that may leave you with strong feelings of déjà vu – in North Carolina.

The Details

On Friday morning Charlotte officials held a press release notifying the public that PCBs were discovered in the Mallard Creek Wastewater Treatment Plant (WWTP). They repeatedly emphasized that drinking water was not affected, but advised area residents to avoid contact with downstream water in Mallard Creek and Rocky River as a precaution.

Although complete details are still missing, authorities believe that PCBs and other organic chemicals were deliberately dumped into the sewer behind a local grocery store, which is situated about 10 miles upstream “as the pipe flows.”   They suspect the act was an attempt to avoid high waste disposal costs, and believe the illegally discharged amount was significant; noting that septic trucks can carry between 3,000 and 5,000 gallons of sewage.

The contamination was discovered on Thursday February 6th, 2014 when WWTP employees noticed a sheen on the water in the retaining pond; prompting the plant to shut down until Friday morning. Tests revealed concentrations of 26 ppm PCBs coming into the plant, as well as 10 ppm trichlorobenzene. For more information see the article and pictures by the Charlotte Observer.

Tracing the Stain

As with the South Carolina incidents officials don’t know exactly where the PCBs have come from. Many of the news articles note that PCBs were used in transformers and capacitors, and others go as far to include caulk and paint; however the source and culprit are still unknown.

With so few details, it’s difficult to infer much at this point in time, however the fact that trichlorobenzene is a constituent hints that some of the oil may have been from an old transformer.


Until 1977, PCB-containing transformers also contained chlorinated benzene, added to increase viscosity. Trichlorobenzene, tetrachlorobenzene, or a combination of the two, were mixed with PCBs and sold as “askarel” – a generic term for a synthetic dielectric fluid comprised of chlorinated aromatic hydrocarbons. Askarels were also used in capacitors, but the formula typically contained only PCBs.

So did someone just dump the contents of a transformer into the sewer?

Likely not. PCB Askarel Transformers typically contained concentrations of PCBs ranging from 450,000 ppm to 800,000 ppm. The low levels of PCBs found in the treatment plant indicate to us that the dumped materials were probably contaminated with askarel transformer fluid.

Of course further testing to identify the constituents will give us a better idea of the type and source of the illegally dumped oil. It may be that the contamination was from a hodge-podge of waste materials in which trichlorobenzene was a constituent, unrelated to PCBs; yet even information such as this could give us a better idea of where and from whom it came from, details which may help prevent further incidents, and allow the City of Charlotte to hold someone accountable.

Catching the Cat & Cleaning the Stain

Not only is the Charlotte-Mecklenburg Police Department investigating the incident, but an interagency task force comprised of the Charlotte Fire Department, EPA Criminal Investigation Division, Charlotte-Mecklenburg Utilities Department, and NC Highway Patrol is also involved. As of Friday and Saturday, surveillance video was already being reviewed, and the task force is conducting interviews of witnesses and other persons of interest.  In addition the Fire Department may conduct additional chemical tests on locations and vehicles identified through the investigation.

The memo released by the Police Department also indicates that the most serious charges could range from state to federal felonies.  If the Department of Justice’s prosecution of deliberate mishandling of PCBs in North Carolina is any indication of the severity of the Police Department’s charges – then the culprits should be worried.

“Enforcing our environmental laws is essential to protecting the health of North Carolina’s residents and their natural resources,” said Robert G. Dreher, Acting Assistant Attorney General for the Justice Department’s Environment and Natural Resources Division.  “PCBs are well known to pose substantial risks to human health and the environment and must be handled responsibly and lawfully.  We will continue to vigorously prosecute those who ignore the laws Congress enacted in order to protect the people and the environment from coming into contact with this toxic substance.”

Unfortunately whatever the source, and whoever the culprit, the cleanup will be expensive, as the experiences in South Carolina have indicated. We can only hope that this is an isolated incident, and no other treatment plants will be affected. As information becomes available we’ll be sure to update our posts.

Submitted by Kate McMahon, Research Associate


  1. What an immense read, post more often please! 

    Amela Jones
    waste water services

    1. Thanks Amela! We should have more soon.

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