What does it mean that nine of the 42 wells tested near the airport for PFOS and PFOA, were found to have some and 33 wells were found to have none.
According to Greensboro Water Resources Assistant Director Michael Borchers it’s good news. Borchers said, “That’s really good news. They want to do a little more investigation, but it doesn’t look like we have a significant issue with ground water.”
Only three of the wells had a level of PFOS and PFOA that was high enough to be accurately tested and all of those were well below the Environmental Protection Agency health advisory of 70 parts per trillion. The other six wells had such a tiny amount of the chemicals that the state wasn’t comfortable releasing a figure.
The tests are for parts per trillion which is hard for most people to imagine, but one comparison is one part per trillion is equivalent to one second out of 32,000 years. Another comparison is one part per trillion is equal to one drop of water in an Olympic-sized swimming pool. It’s a lot smaller than tiny.
What Borchers said is that the testing indicated that they were on the right track in looking for the source of the chemicals. The current theory is that one of the prime sources has been the use of fire fighting foam at the Piedmont Triad International Airport. What the testing indicates is that the PFOS and PFOA have not migrated down into the ground water but are largely confined to the surface runoff.
One of the mysteries has been that the levels at the Mitchell Water Treatment Plant where the water from Lake Brandt is treated go up at times of heavy rain when you might expect the chemicals to be more diluted.
However, if it is surface pollution times with more runoff could be causing the chemicals to flow directly into the lake when under normal conditions they would simply stay in place.
Borchers said the testing indicated that surface waters have a much higher degree of influence than groundwater.
Once a pollutant gets into the ground water it is incredibly hard to remove it. Removing contaminants from the surface may not be easy but it isn’t impossible.
According to Borchers if the wells had shown levels of PFOS and PFOA that were approaching or exceeding the health advisory level, Greensboro was ready to provide those homes with city water.
Borchers said that the chemicals had been used for the past 50 years, and the indications are that they have not migrated into the groundwater, which is good news for the well owners and also for Greensboro that would have to run the waterlines out to the homes.
Greensboro has a temporary system to treat the water at the Mitchell plant which has exceeded the health advisory limit and has already purchased the land to build a permanent system at a cost of an estimated $30 million.
When the water at Mitchell did exceed the 70 parts per trillion health advisory, the city simply shut the plant down and used water from other sources. No problems have been detected in the water from Lake Townsend which is much larger reservoir than Brandt and also farther from the airport the suspected source of the contaminants.