Jump to main content.


Ecological Risk Assessment

Frequently Asked Questions

Analytical Considerations

  1. For the ecological risk assessment, how do I determine what chemical contaminants must be included in the analyses of site samples?
  2. Can the ecological risk assessment focus on only the contaminants known to be handled onsite?
  3. How do I evaluate duplicate samples with different results?
  4. How do I evaluate "Non-Detects"?
  5. How do I determine what analytical detection limits should be used for data that is going to be used for an SERA?

1. For the ecological risk assessment, how do I determine what chemical contaminants must be included in the analyses of site samples?

In general, during the planning for the initial problem phase (i.e., data collection) the full suite of TAL/TCL compounds should be strongly considered. The analytical suite may be tailored to site-specific conditions (i.e., historical data and/or knowledge), however the revised suite must include, at a minimum, all site-specific COPCs and their daughter products. If less than a full scan is proposed and warranted, field screening techniques should be utilized to verify that there are no "surprises."

[ Back to Top ]

2. Can the ecological risk assessment focus on only the contaminants known to be handled onsite?

The screening steps of the risk assessment (Steps 1 and 2) must evaluate all of the available analytical data (i.e., the entire suite of compounds for which analyses were performed).

[ Back to Top ]

3. How do I evaluate duplicate samples with different results?

The greater or more conservative result should be used. If you have duplicate samples with one sample yielding a "detect" but the second sample yielding a "non-detect" and the detected value is lower than the non-detect, the detected value will be used in the screening ERA.

[ Back to Top ]

4. How do I evaluate "Non-Detects"?

In cases where the detection limits were higher than the screening values, ½ of the detection limit should be used in determining the number of samples exceeding the screening values and completing the comparison with the benchmarks. If the detection limits were lower than the benchmark, it can be assumed that chemical was not present in the sample at levels which are of concern.

[ Back to Top ]

5. How do I determine what analytical detection limits should be used for data that is going to be used for an SERA?

In general, the detection limits should be lower than the screening level benchmarks. However, the selection of analytical methods and the resultant detection limits is site specific and is usually negotiated during the work plan development phase of a project. Regardless of the method and limits selected, or the detection limits actually achieved, chemicals of potential concern whose detection limit is greater than the corresponding screening value must be carried through into Step 3 of the ERA process.

[ Back to Top ]

Region 3 | Mid-Atlantic Cleanup | Mid-Atlantic Risk Assessment |EPA Home | EPA Risk Assessment Homepage


Local Navigation


Jump to main content.