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Kingston Ash Release

Air Monitoring: Summary of Metals Analysis Results

Results-at-a-Glance

TVA collected filter-based samples for metals until August, 2011. Analysis of over two years’ results shows that:

  • Action levels for arsenic and silica specified in the Ambient Air Monitoring Plan (AAMP) have never been exceeded.

  • Eight of the 12 metals [including arsenic and hexavalent chromium (Cr(VI))] had concentrations in coal ash within the ranges found in naturally occurring local soils, and therefore, cannot be distinguished from background.

  • The four metals in ash found to have concentration ranges above those found in local soils are all below their respective soil risk-based screening levels (RBSLs).

  • Monitored concentrations in air for 10 of the 12 metals and silica are either below their respective air Risk-Based Screening Levels (RBSLs), or no applicable air RBSL exists.

  • Arsenic and projected Cr(VI) concentrations rarely exceeded their respective air RBSLs and do not pose a risk to human health. Any detected concentrations could not be distinguished from background levels. Cr(VI) is not biologically available in coal combustion products.

 

Background

The original Ambient Air Monitoring Plan (AAMP) presented technical justifications to limit analysis of filter-based samples to arsenic, thallium, and silica. As better bulk ash data became available, thallium was removed from the list. TDEC samples for ten other metals, which TVA later added as a redundant measure to confirm TDEC’s sampling and analysis.

The following table lists the twelve elements for which analyses were performed and summarizes analytical results for TVA samples collected March, 2009-July, 2011.

Analyte

Unit

Minimum Detected Result

Maximum Detected Result

Average Detected Result

Frequency of Detection

Aluminum

μg/m3

0.0229

0.67

0.133684

157/243

Arsenic

μg/m3

0.000032

0.0079

0.00111

369/935

Barium

μg/m3

0.0022

0.0422

0.007225

120/243

Beryllium

μg/m3

0.0000043

0.00028

0.0000506

37/243

Cadmium

μg/m3

0.000018

0.00062

0.000113

176/243

Chromium

μg/m3

0.00105

0.00297

0.002224

7/243

Lead

μg/m3

0.000709

0.00768

0.002809

235/243

Manganese

μg/m3

0.0014

0.019

0.005263

216/243

Silica

μg/m3

2.0

3.2

2.6

4/585

Selenium

μg/m3

0.00029

0.00397

0.001154

118/243

Thallium

μg/m3

0.000005

0.00019

0.0000773

34/420

Vanadium

μg/m3

0.0000088

0.0052

0.001488

37/235

 

Analysis of Results

Comparison with Regional Soils and Risk-Based Screening Levels for Residential Soils
Four constituents detected in TVA ash samples (Barium, Beryllium, Thallium, and Vanadium) had maximum concentrations that exceeded the range for soils in the region, but did not exceed the EPA regional residential risk-based screening level (RBSL) for residential soils.

Arsenic concentrations in TVA ash samples were within the range reported for regional soil. While the average arsenic concentration reported for regional soil is 19.3 mg/kg, the region’s maximum detected concentrations do exceed the RBSL.  Project action levels were never exceeded and any detection in air was indistinguishable from normal background levels.

Chromium concentrations reported in TVA ash samples were within the range reported for regional soil. The maximum detected concentration of total chromium (66 mg/kg) was well below the residential soil RBSL (120,000 mg/kg) for Cr(III). Trivalent chromium was the predominant form found in samples and the trace amounts of Cr(VI) found in coal combustion products are fused in aluminosilicate glass and are essentially inert.

Since there is no residential soil RBSL for silica, TVA could not compare results for crystalline silica in coal ash with a RBSL.  However, the project action level for silica (24-hour average of 10 μg/m3) was never exceeded.

Comparison with Air Risk-Based Screening Levels

Arsenic was detected in approximately 42 percent of air samples, total chromium was detected in approximately 2 percent of samples, and silica was only detected in 1 out of 291 samples.

The US EPA Mid-Atlantic Risk Assessment web-site was used to calculate RBSLs for metals in air assuming a 5-year exposure duration (5 years is the estimated duration of the KIF Ash Recovery Project).

The following table presents a comparison of results to RBSLs for air at Station PS07, downwind of the Kingston site.

Analyte

Screening Level1 (μg/m3)

Maximum Detected

Results Above RBSL

Number of Measurements

Arsenic, Inorganic

0.00340

0.00790

8

447

Chromium(III),Insoluble Salts

NA

0.00279

NA

116

Chromium(VI)

0.0000167

0.00279

2

116

Silica (crystalline, respirable)

3.13

2.00

0

291

1 = Screening levels are based on a 5-year exposure duration.
NA = Not Applicable. Toxicity values for the inhalation pathway are not available for this constituent.

 

 

“The particulate matter and metals measured in air near the site are below national and state standards or are less than any levels of concern.” 

Tennessee Department of Health

           
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