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Division Approach to Soil Screening Values

 

The division uses the EPA Regional Screening Levels (RSLs) to determine whether levels of contamination found at a site may warrant further investigation or cleanup, or whether no further investigation or action may be required.

 

Screening Levels for Residential and Industrial Worker Exposure Scenarios

 

The division uses the direct exposure levels for residential and industrial exposure scenarios listed in the EPA Regional Screening Levels (RSLs).  This table, which EPA updates on a regular basis, can be found at:

 

http://www.epa.gov/reg3hwmd/risk/human/rb-concentration_table/Generic_Tables/index.htm

 

Please use one of the links to the Summary Table in the top row of links.

 

A benefit of adopting the national approach to calculating screening levels is that EPA also has a Calculator that can be used to adjust the input parameters for the purpose of coming up with site-specific screening levels.  A link to this feature is provided on the web page referenced above. A useful background document and User's Guide identifying the toxicity values, equations and exposure assumptions used to calculate Regional Screening Levels is also provided on this web page.

   

Screening values presented in the Regional Screening Levels table are based on human health risk from the combined exposure of direct soil ingestion, dermal contact with soil, and inhalation of vapors or particulates associated with soil.  Other pathways, such as indoor air or food chain effects, may need to be consdered on a site-specific basis.  Users should also be aware that some sites in sensitive ecological settings may need to be evaluated for potential ecological risk.  In addition, please continue to take into consideration the following:

 

  • Colorado Department of Public Health and Environment-specific toxicity values such as an inhalation Reference Concentration (RfC) of 7.0 ug/m3 for 1,1-dichloroethylene (1,1-DCE) and an oral Reference Dose (RfD) of 0.0011 mg/kg/day for diisopropyl methylphosphonate (DIMP).
  • For facilities where multiple non-carcinogenic chemicals are present, HQ values should be divided by a factor of 10 to account for additivity.  If adjusted tables values are exceeded, consultation with a toxicologist is recommended to assess likely impact on specific target organs.
  • For lead, consideration of site-specific inputs to the IEUBK or ALM lead models and consultation with a toxicologist is strongly recommended for facilities with lead levels in soil that exceed the residential or worker table values.  Contact the Division for additional information about details of the lead models and site-specific considerations.
  • For workers at facilities where soil-intensive use is anticipated, additional analysis and consultation with a toxicologist will be required to determine appropriate site-specific inputs to the risk equations.

 

Screening Levels Protective of Groundwater Quality

 

The division uses the Groundwater Protection Level and Leachate Reference Concentration columns in the Groundwater Protection Values (GPV) soil cleanup table, which has replaced the Colorado Soil Evaluation Values (CSEV) table. The last column in this table identifies the water standard used in the calculations which are based on standards and methods established and employed by the Water Quality Control Commission.  

  

Groundwater Protection Values Soil Cleanup Table pdf file  March 2014   NEW   

 

These two columns should be consulted when reviewing site data because in some cases, decisions on whether or not further evaluation or remediation are needed may be based on the mobility of constituents and their potential to reach and degrade groundwater quality.

 

Air Screening Concentrations

 

Although the method by which the division calculates air exposure screening numbers is identical to the method used by EPA, there are a few differences between our Air Screening Concentration Table and air columns listed in the Regional Screening Levels.  You are therefore advised to continue using the division's air table.

 

Air Screening Concentrations Table pdf file   

 

Target indoor air concentrations for those chemicals not included on the division's list may be found in the EPA Regional Screening Levels table.

 

For More Information

 

If you have questions about the derivation or application of these table values, please email comments.hmwmd@state.co.us , putting "Avramenko" in the subject line.