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City Initiates Weekly Sampling to Optimize Response to Elevated Levels of PFOS/PFOA

Post Date:08/07/2018 1:59 PM

With continued levels of perfluorooctane sulfonic acid (PFOS) and related chemical perfluorooctanoic acid (PFOA) detected near and above the Environmental Protection Agency (EPA) established health advisory level, the City of Greensboro has established a weekly sampling protocol to monitor levels in water flowing into Lake Brandt from Horsepen Creek and treated water leaving Mitchell Water Treatment Plant. The weekly sampling will enable the City to predict the timing and amount of additional treatment needed to reduce the levels of PFOS/PFOA in drinking water.

Results received this week showed levels of combined PFOS/PFOA at 96 parts per trillion (ppt). EPA established the health advisory level at 70 ppt, which means that a lifetime of drinking water at levels above 70 ppt increases risk of certain adverse health effects for the most sensitive human populations. More information about EPA’s findings can be found online.

The City is immediately taking these proactive steps to reduce levels of PFOS/PFOA:

  • Installing temporary treatment equipment at the Mitchell Water Treatment Plant for feeding powdered activated carbon (PAC). Equipment has been located for the system, and plans for delivery and installation are underway. Testing to ensure proper and effective setup will be needed before the equipment is fully operational.
  • Planning efforts to construct permanent treatment upgrades at the Mitchell Water Treatment Plant that address PFOS and PFOA through Granular Activated Carbon (GAC) treatment methods.

While no drinking water regulatory limit has been violated, the City remains committed to resolving this issue. Meanwhile, the Mitchell Water Treatment Plant needs to operate intermittently to address operational issues such as fire protection needs and water demands. However, the amount of water coming from the plant will be kept at a minimum until the temporary treatment system is operational.

“The factors that influence the amount of PFOS and PFOA making its way into the City’s water makes the study complex, however we continue to sample so that we can make good data-driven decisions. We have complete confidence in the treatment approach we have committed to take. Testing has shown that using PAC in our treatment process is very effective at removing these compounds and it is a key element in our approach to drive and maintain the levels below the health advisory level,” said Assistant Director of Water Resources Mike Borchers.

For the latest information and ongoing updates about this issue, visit

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