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Risk Evaluation

When contamination occurs, it is important to determine whether it presents a human health risk, such as contaminated soils or ground water releasing harmful vapors into the air inside living or working spaces, contaminated ground water polluting a drinking water well, or contaminated rivers and lakes impacting drinking water systems and effecting recreationists.

The risk evaluation process is used to characterize the nature and extent of health risks to humans and ecological receptors from chemical contaminants and other factors that may be present in the environment.

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DEQ created the Risk Evaluation Manual for Petroleum Releases to evaluate whether contaminated ground water, surface water, or soil at a particular location poses a human health risk. The manual helps to evaluate whether a petroleum release investigation or cleanup is needed and, if so, its scope and nature.

The manual provides a consistent method for addressing contamination, describes the risk evaluation process and includes information on implementing important parts of the process, such as evaluating the vapor intrusion pathway.

The companion software is used to input site-specific parameters to estimate risk and develop remedial action target levels. The software will be updated to reflect 2018 toxicity updates.

Download the manual:

Download the software and user guide below. (Instructions)

The following spreadsheets assist in evaluating risk:

  • Mann-Kendall Calculator: A spreadsheet to conduct a Mann-Kendall analysis of trends for up to five chemicals and 10 sampling events.
  • UCL Calculator: A spreadsheet to calculate the 95% upper confidence limit (UCL) of the mean for chemical concentration data. The utility calculates the 95% UCL for normal and log-normal distributed sample data, as well as a bootstrap estimate.

The EPA Regional Screening Levels and associated risk calculator or another DEQ-approved risk assessment approach can be used to determine risk-based criteria for nonpetroleum chemicals of concern, such as metals and solvents.

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