Protecting Public Health and the Environment.

Risk Evaluation Manuals

Addressing Contamination—Evaluating Risk

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 affecting recreationalists.

DEQ created two guidance documents, 2004 Risk Evaluation Manual (REM) and 2012 Risk Evaluation Manual for Petroleum Releases (Petro REM), to evaluate these risks from discovering contamination through cleanup to determining whether ground water, surface water, or soil at a particular location is contaminated to the extent it poses a human health risk. The manuals guide DEQ employees and others in responding when chemicals are released to the environment. They help evaluate whether an investigation or cleanup is needed and, if so, what its scope and nature should be, providing a consistent method for addressing contamination.

The original 2004 REM addresses a wide range of chemicals, such as metals, herbicides, chlorinated solvents, and petroleum hydrocarbons. The 2012 Petro REM was developed to implement the Standards and Procedures for Application of Risk Based Corrective Action at Petroleum Release Sites (IDAPA 58.01.24), codified in May 2009 and revised in March 2012. The Petro REM replaces the procedures previously described in the REM for a prescribed list of petroleum-related chemicals commonly found at petroleum release sites. The 2004 REM can still be used for other classes of chemicals.

2012 Risk Evaluation Manual for Petroleum Releases

The Petro REM includes a manual and software reflecting revisions based on comments received during a public comment period held August 3–31, 2011. The manual consists of six sections describing the risk evaluation process and 12 appendices that provide supporting information and guides on implementing important parts of the process, such as evaluating the vapor intrusion pathway.

Download the manual here:

The software includes only the petroleum chemicals of interest specified in the rule. It incorporates toxicity factor values from the revised rule, and EPA's recommendations on chemical-specific fate and transport property values. Incorporating EPA's recent guidance, the software also provides calculations for inhalation risk and early childhood risk to mutagenic chemicals.

The software was originally developed as an Excel spreadsheet. DEQ has replaced the spreadsheet with a standalone Windows application that does not require additional software like Excel. Excel files will no longer be available or accepted for use.

Improvements to the new software include:

  • A user-friendly graphical interface and step-by-step process
  • A screening level evaluation step
  • Significantly smaller file sizes for individual simulations
  • Links to the petroleum risk evaluation rules, guidance, and user guide
  • Original application errors corrected

Download the software and user guide below. (Instructions)

2004 Risk Evaluation Manual and Software

The REM consists of 12 sections describing the risk evaluation process and 14 appendices. The appendices contain supporting information to assist in implementing the evaluation process. Note: The 2004 REM should not be used to complete risk evaluations for chemicals associated with petroleum release sites. 

Download the manual here:

The following spreadsheets are also provided to assist in evaluating risk:

  • Risk Evaluation Software: A computational spreadsheet to calculate risks and target levels.
  • Mann-Kendall Calculator: A spreadsheet to conduct a Mann-Kendall analysis of trend for up to 5 chemicals and 10 sampling events.
  • UCL Calculator: A spreadsheet to calculate the 95% upper confidence limit (95% 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.

Training Opportunities

DEQ periodically offers training on the Petro REM. Check DEQ’s Conferences, Trainings, and Workshops web page to learn of upcoming training opportunities.  

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Staff Contacts

Voluntary Cleanup Program Manager
Derek Young
DEQ State Office
Waste Management & Remediation Division
1410 N. Hilton
Boise, ID 83706
(208) 373-0525

More Information

U.S. EPA Regional Screening Levels

Related Pages

Environmental Covenant

Leaking Underground Storage Tanks in Idaho