Environment

Groundwater wells near Marshall, Cliffside coal ash basins have a thallium problem

     Map of basin locations at the Cliffside plant in Catawba County (Duke Energy)

This post has been updated with radium results at the Marshall plant.

Elevated levels of thallium, a cancer-causing chemical element often found in coal combustion residuals, was detected in more than a quarter of samples taken from groundwater wells near Duke Energy’s Rogers/Cliffside plant in Cleveland and Rutherford counties. At Marshall, in Catawba County, 20 percent of the samples contained high levels of thallium.

Ten to 12 separate chemical contaminants were detected in groundwater wells at Marshall and Cliffside. A full list and the ranges of levels about the groundwater standard are listed below.

The results were disclosed as part of Duke Energy’s federally mandated groundwater reports, which totaled 20,000 pages. NC Policy Watch wrote last week about contamination near four of the plants, and is reporting on the remaining seven this week.

Map of basin locations at the Marshall plant in Cleveland/Rutherford counties

The groundwater wells are not used for drinking water, and they all lie within Duke Energy’s compliance boundary. However, in general, groundwater travels, and depending on the slope and geologic formations, it can enter drinking water wells, as well as lakes and streams. In the case of thallium, it can build up in fish tissue.

At Marshall, three of 63 samples tested high for radium; one of those samples was more than twice the drinking water standard.

In the tables below, the radium was calculated using a margin of error included in the documents.

Cliffside    
27 wells236 samples
ContaminantMaximum contaminant level/interim standardRange of exceedances, lowest to highest (ppb)Number of exceedances% of samples that exceeded maximum contaminant levels
Antimony1 ppb1.110.4
Arsenic10 ppb10.3 – 37.320.8
Beryllium 4 ppb4.6 – 9.920.8
Boron 700 ppb719 – 273010042
Cadmium2 ppb6.1 – 1420.8
Chloride250 ppm32110.4
Chromium10 ppb12.3 – 58.1114.6
Cobalt 1 ppb1.1 – 74618578.3
Sulfate250 ppm258 – 8183012.7
Selenium 20 ppb21.7 – 1172611
Thallium .2 ppb.21 – 2.16427.1
Radium5 ppbNo exceedances

 

Marshall    
39 wells (including background)317 samples
ContaminantMaximum contaminant level, groundwater and drinking waterRange of exceedances, lowest to highest (ppb)Number of exceedances% of samples that exceeded maximum contaminant levels
Antimony1 ppb1.2 – 2.651.5
Arsenic 10 ppb9.5 – 16451.5
Beryllium 4 ppb5 – 5.7113.4
Barium 700 ppb706 – 2830278.5
Boron 700 ppb12 – 58109329.3
Chloride 250 ppm251 – 362247.6
Chromium 10 ppb10.7 – 39.2237.3
Cobalt 1 ppb1.1 – 21614545.7
Selenium 20 ppb21.3 – 42.361.8
Thallium 0.2 ppb0.22 – 3.66420
Radium*5 ppb5.53 – 14.183 of 63 samples
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