Environmental Sampling in Henry County, Missouri

1

Figure 1.0

The locations where sediment and surface water samples were taken are not shown on Figure 1.0.

2

General Comment

The report does not explain how the samples for drinking water, soil, and sediment were collected.

3

General Comment

The report does not include a Quality Assurance Project Plan (QAPP) for the sampling work, nor any goal for data quality. Generally, a QAPP is used to define the criteria and processes used to ensure and verify that the data met specific data-quality goals.

4

Pg. 2, Potable Water Sources

The report says that some potable water samples have elevated levels of lithium. However, it is not clear what elevated means because a screening value is not provided. See sample locations 2855, 893, 1067, 565, 365, and 855.

5

Pg. 2, Potable Water Sources

The report concludes on Pg. 2 that, as summarized in Table 1.0, “506 and 2499 potable water sources exceed EPA Maximum Contaminant Level (MCL) for Lead.” However, Table 1.0 identifies 0 mg/L as the EPA MCL, instead of 0.01 mg/mL, which is the correct EPA MCL for lead. EPA concludes that Table 1.0 mistakenly uses EPA’s Maximum Contaminant Level Goal (MCLG) of 0 mg/L, which is a non-enforceable public health goal. The reported concentration for 506 and 2499 appear to be 0.0014 and 0.0034 mg/L, respectively. Both reported values are below the lead MCL value of 0.01 mg/L.³

6

Pg. 2, Potable Water Sources

The report claims that a potable water source has cobalt levels above the EPA MCL. However, there is no established EPA MCL for cobalt.³ See sampling location 2499.

7

Pg. 2, Potable Water Sources

The report says that a potable water source has sulfate levels higher than the EPA MCL. However, there is no EPA MCL for sulfate. Please note, there is a secondary MCL safety limit guideline of 250 mg/L for sulfate, which is based on taste and smell, but it is not enforced by EPA.³ See sampling location 855.

8

Pg. 2, Surface Water Sources

The report says that cobalt levels in samples collected from the Montrose Lake and 2499 Lake locations are above the EPA MCL, but there is no EPA MCL for cobalt. It also mentions that boron levels are above the EPA MCL, but there is also no EPA MCL for boron.³ See 2499 Lake and Montrose Lake sampling locations.

The report on Pg. 2 summarizes that Montrose Lake sample exceeded the EPA MCL for total radium (226 and 228). The results for total radium in Montrose Lake are below the EPA MCL of 5 pCi/L. According to Table 1.0, the total radium level is 2.556 pCi/L.³

The report on Pg. 2 summarizes that a Montrose Lake sample exceeded the EPA MCL for total radium (226 and 228). However, the description of that sample reveals that it was a soil sample evaluated according to default target levels (DTLs) and/or EPA Region 7 Screening Levels and not an EPA MCL.

9

Pg. 3, Nov. Sampling Event

It is unclear how a soil sample was collected from the location “Davis R 12 Roof (roof gutters).” The report states that soil samples were obtained from the top 2 inches of soil at each location, but does not mention any specifics regarding the gutters.

10

Pg. 3 & Table 1.0

The report states that soil samples were evaluated using DTLs or EPA Regional Screening Levels (RSLs). The DTL target levels came from Table B-1 of the technical guidance, which lists the lowest target levels for soils.⁶ These target levels were used to see if soil sample concentrations could affect domestic groundwater use.⁶ As a result of this comparison, hexavalent chromium, barium, cadmium, silver, lead, and selenium appear to be compared to the DTL soil values for the protection of the domestic groundwater use pathway (GWP).⁶ However, EPA recommends that the residential soil RSLs be used when comparing residential soil samples. Mercury appears to be compared to the DTL soil values for the indoor inhalation pathway (INH).⁶ It is unclear why different pathways are chosen for different contaminants.

Further, in Table 1.0, cobalt and boron values are reported to be compared to a value derived from a “Health Advisory.” The health advisory source for the cobalt and boron values have not been identified at this time.

11

Pg. 3 & 4

The report claims that four soil samples have boron levels above state target levels (DTLs). However, there is no DTL for boron. According to Table 1.0, the boron value is actually based on a “Health Advisory” level.⁶ The source of this health advisory level is not known. See sampling locations 506, 555, Davis-Main, and Davis Roof.

12

Pg. 3 & 4

The report says that 11 soil samples have cobalt levels above state target levels (DTLs), except for four samples collected at the school. However, there is no DTL target level for cobalt, and Table 1.0 shows that the cobalt value is based on a “Health Advisory” level.⁶ The source of this health advisory level is not known.

13

Pg. 3 & 4

The report mentions that one soil sample from the school roof exceeded the state default target level (DTL) for selenium. However, since this sample was taken from the roof gutters, it is not clear if comparing it to soil values is appropriate.

14

Pg. 4, Conclusions

Soil exceedances of hexavalent chromium, lead, arsenic, boron, cobalt, and selenium may be the result of comparison to the wrong DTL values based on exposure pathway.⁶

15

Figure 1.0

The Davis R 12 school is shown in the wrong place on the map. It should be 1.7 miles north of where it is marked. There do not appear to be buildings where the school is labeled.

16

General

Deep Blue Creek is referenced in the report, and it is not known if this is meant to be Deepwater Creek or a different stream.

17

Table 1.0

In general, it appears that background concentrations were not determined. Determination of background concentrations is an important step in evaluating the data to determine if any of the values reported for contaminants exceed selected risk levels.

18

Table 1.0

Sediment/soil ecological screening values may not have been appropriately applied, because of the lack of information on background concentrations of the contaminants that should be first determined. Background concentrations would need to be determined to identity if any constituents were detected above background levels.

19

General Comment

To protect the privacy of residents, the names and addresses of private well owners should not be published or used for identification purposes.

20

General Comment

The report incorrectly states that “EPA Region 7 Screening Levels” were used in conjunction with state target levels (DTLs) to assess sample results. However, review of the report reveals that for potable and surface water, the EPA MCLs were used for comparison, which are not the same values as “EPA Region 7 Screening Levels.”

To reference, for screening purposes, EPA uses Regional Screening Levels (RSLs) set to a target cancer risk of 1 in a million (1E-06) and a non-cancer hazard quotient of 0.1. Potable water is screened using EPA RSLs for residential tap water. The soil-to-groundwater pathway is assessed using a dilution attenuation factor of 20 in EPA Region 7, along with direct contact assumptions for residential and commercial receptors. For radionuclides assessment, EPA recommends using default parameters in the EPA Preliminary Remediation Goals (PRG) calculator. This information is referenced in the EPA OSWER Memorandum 9285.6-20, "Distribution of the 'Radiation Risk Assessment at CERCLA Sites: Q&A'."

21

General Comment

The report’s comparison criteria do not differentiate between receptors and exposure pathways. This approach also overlooks the extent to which site contaminants contribute to the overall lifetime cancer risk and non-cancer hazard index. Remedies under EPA cleanup programs, like the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and the Resource Conservation and Recovery Act (RCRA), should generally aim to reduce risks so that the excess cumulative lifetime cancer risk from site-related exposure falls between 1 in 10,000 (1E-04) and 1 in a million (1E-06), according to EPA’s “Rules of Thumb for Superfund Remedy Selection” (EPA 1997).

22

General Comment

The report does not specify the analytical methods and detection/reporting limits, though they are noted in the analytical data package. This information should be included in the report to validate the data, compare it to standards, and ensure that the right methods are used. Any future sampling reports should also include this information.

23

General Comment

Although some basic quality assurance/quality control (QA/QC) information is included in the analytical data, the report does not provide a data quality evaluation or validation.

24

General Comment

The analytical methods provide for a temperature in which samples are to be kept for testing. The laboratory analytical package reveals that all samples were received by the lab at higher than what is required by the analytical methods. This could impact the quality of the data.

25

General Comment

The analytical methods provide for the maximum time a sample should be kept before it is tested. Hexavalent chromium exceeded the holding times in several samples. Several dilution factors were used that elevated results often above screening levels. The quality and usability of the analytical data cannot be determined without a data evaluation or validation.

26

General Comment

The report does not mention whether a Missouri-certified laboratory was used for the drinking water analyses.

27

General Comment

For water (aqueous) samples, future sampling should also include chemistry indicator parameters like temperature, pH, oxidation/reduction potential, dissolved oxygen, and hardness. The report did not contain this information.

28

General Comment

The typical EPA approach for assessing residential yards for exceedances of EPA Regional Screening Levels (RSLs) or Removal Management Levels is to collect at least a five-aliquot (i.e., portioned) composite soil sample.

29

Tables

The detection limits for several soil and sediment samples are higher than the EPA RSL for hexavalent chromium, which raises concerns about data quality and makes it difficult to assess the impacts. The EPA RSL for hexavalent chromium is 0.95mg/kg, which is much higher than the state target level listed in the table for soil.

30

Tables

Radium and other radionuclides, such as thorium and uranium, can be elevated naturally in the Pennsylvanian-aged strata (especially shales) in this area, which may impact soil, sediment, and surface water. As stated above, radium and other radionuclides, like thorium and uranium, can naturally be at high levels in the subsurface, especially in shales, in this area. This may affect soil, sediment, and surface water. Before attributing these elements to a specific source or release, a thorough background evaluation of all naturally occurring parameters at this site should be considered.