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Ecological Risk Assessment Step 6

Sections of Step 6 Baseline ERA (BERA) Site Investigation and Data Analysis:
Step 6 of the Superfund Ecological Risk Assessment 8-step process is Site Investigation and Data Analysis.

Site Investigation

This is the application of the Workplan (WP) and Sampling Analysis Plan (SAP) that were created in previous steps (Step 4 - Development of the WP and SAP). If any revisions to the WP or SAP were required as a result of the Field Verification process (Step 5), they should all be included as well. During the sampling process, the data quality objectives should be strictly adhered to, as failure to do so can significantly alter the interpretation of the data.

Even at this stage there might be unexpected complicating factors that have arisen since the Field Verification, such as the extent of contamination being different than expected or new contaminants are discovered. If there are new issues to be considered, the WP/SAP might have to be modified to accommodate these new considerations. Otherwise, the sampling and analysis may proceed with the WP/SAP as is.

Analysis of Ecological Exposure and Effects

Characterizing Exposures

Exposure is the situation where a contaminant (stressor) is present at the same place and time as, or is in contact with, a plant or animal. The exposure analysis results in the creation of an "exposure profile" which describes the extent of the exposure and the patterns of exposure over space and time. The profile also describes how these patterns relate to the assessment endpoints and risk questions developed in the Problem Formulation step (step 3). 

When investigating chemical contaminants at a Superfund site, mathematical models of how contaminants move within the ecosystem combined with sampling data are used to predict the current and future nature and extent of contamination at the site. In addition, information gathered from the site is used to replace assumptions based on information from literature sources or from other sites. Any remaining assumptions and uncertainties should be documented. 

Characterizing Ecological Effects

Exposure-response analysis:

The results of this analysis describe the relationship between size, frequency, or duration of a chemical contaminant and the size of the response. The relationships between the assessment endpoints and their respective measures of effect are also described (see Step 3). This type of analysis can help a risk manager to determine the tradeoff between the level of cleanup and likely benefits of that cleanup. The risk manager can also determine the balance of ecological and financial costs versus benefits of different cleanup options. If exposure-response analyses cannot be done, LOAELs and NOAELs can be developed instead (as in Step 2), but information gathered from the site should be used instead of conservative assumptions

Evidence of causality:

It is important at Superfund sites to determine how likely it is that the contaminants found at the site actually cause the effects on the measurement and assessment endpoints. The evidence for this relationship should come from multiple sources and not just the exposure-response analysis.

This evidence, along with the other data analyses, helps the risk manager to determine the cleanup remedy for the site, including: what media (sediments, soil, water) need to be cleaned up, where at the site the cleanup needs to be directed, and to what extent (i.e., how much contamination can be left behind and not cause further ecological risk).

Scientific-Management Decision Point

A Scientific-Management Decision Point (SMDP) is only needed in this step if there were changes to the Work Plan or Sampling-Analysis Plan, including possible changes to the measurement endpoints and associated testable hypotheses.

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