Change to the Use of the U.S. Environmental Protection Agency Regional Screening Levels as the Primary Remedial Objectives for Air, Soil and Groundwater
What has changed
In October 2020 the we changed the “Air, Water and Soil Remedial Objective” portion of our website to eliminate the links to several tables that formerly provided cleanup/screening values that had been developed by our personnel.
From now on when you search for guidance and policy information on the division’s website by following one of the links specified below you will no longer find the “Groundwater Protection Values (GPVs) soil cleanup table (dated March 2014)” and the “CDPHE Air screening concentration table (dated January 2016)” since we will no longer be using them. Instead, we have changed to exclusive use of the U.S. Environmental Protection Agency’s (EPA’s) “Regional Screening Levels (RSLs)” as cleanup levels/screening levels for all environmental media. We will continue to use standards and method established and employed by the Colorado Water Quality Control Commission as the primary source of surface water and groundwater cleanup levels. EPA RSLs for water may be used when there is no Colorado water standard for a chemical, or in other very specific circumstances.
The division website pathways that are effected
- Topics/Environmental cleanup/Cleanup guidance and policy/Guidance and policy/Air, water and soil remedial objectives/Screening levels protective of groundwater.
- Topics/Hazardous Materials and Waste Management guidance and policy/ Environmental cleanup/Cleanup guidance and policy/Guidance and policy/Air,
- water and soil remedial objectives/Screening levels protective of groundwater.
- Topics/Environmental cleanup/Cleanup guidance and policy/Guidance and policy/Air, water and soil remedial objectives/Air screening concentration table.
- Topics/Hazardous Materials and Waste Management guidance and policy/Environmental cleanup/Cleanup guidance and policy/Guidance and policy/Air, water and soil remedial objectives/Air screening concentration table.
The link via those pathways now takes a person to the most recent version of the EPA RSL Summary Table (TR=1E-06, HQ=1). The TR=1E-06, HQ=1 means that the values in the table were calculated using a Target Cancer Risk of One (1) in a Million and a Target Hazard Quotient of 1.0.
The “Resident Air” and “Industrial Air” sub-columns within the main “Screening Levels” Column are to be used when evaluating the results of indoor air samples to determine whether there is a potential human health impact via the air pathway.
The “Protection of Groundwater SSLs” that are found in the rightmost column of the Summary Table are to be used as Screening Levels Protective of Groundwater Quality when evaluating the results of chemical analyses of soil to determine the potential to impact groundwater.
The “Resident Soil” and “Industrial Soil” sub-columns within the main “Screening Levels” column of the Summary Table are to continue to be used as screening levels to determine whether levels of soil contamination at a site warrant further investigation or cleanup.
Get the RSL Summary Table directly from EPAs Regional Screening Levels –Generic Tables website: In the “Summary Table” row and “TR=1E-06, HQ=1” column.
Why was the change made
For many years now the division has required the use of the “Screening Levels” of the most recent version of the EPA’s Regional Screening Level Summary Table with a TR=1E-06, HQ=1 to determine the potential human health impacts when evaluating the results of soil samples from the Facilities that we work with and regulate. However, when evaluating the potential for impacts to groundwater due to soil contamination at these same Facilities, we required the use of the March 2014 Colorado Groundwater Protection Values Soil Cleanup Table. In addition, when evaluating the results of air samples taken to determine the potential indoor air impact from vapor intrusion, we primarily relied on the January 2106 Air Screening Concentrations Table, but also used the EPA RSLs as needed.
The need to reference two different sources when evaluating results of soil and air samples created considerable confusion for our Facilities, especially considering that the EPA Regional Screening Level Summary Table also happens to include “Protection of Groundwater Soil Screening Levels” and the “Resident Air” and “Industrial Air” RSL air values were very similar, but not an exact match.
The original division calculated Screening Levels for soil and air were developed before EPA created the RSLs that they now employ nationwide. A lot of effort is required to ensure that the Screening Levels are kept up to date with new scientific data. In fact, EPA often updates their RSLs twice a year and we would have to request outside help to update our values that often.
For all these reasons, the division decided to eliminate the use of the Colorado Groundwater Protection Values Soil Cleanup Table and the Colorado Air Screening Concentrations Table and use EPA RSLs for all environmental media except water.
Important considerations for use of the EPA protection of groundwater SSLs
The EPA Regional Screening Level Summary Table contains Protection of Ground Water SSLs for many more chemical constituents than the old Colorado table. One thing you will notice is that the Protection of Ground Water SSLs in the EPA tables are typically lower (more conservative) than the values in the old Colorado table were. We recognize there is a concern that the use of lower Protection of Ground Water SSLs will result in an increase in the level of effort and cost for environmental investigations and remediation.
In response, we would like to clarify that the Protection of Groundwater SSLs are generic soil screening levels that can be used as final soil remediation goals if they can be achieved at a facility. If the generic values are not easily achieved, the facility owner may collect and use site-specific information to defend site-specific protection of groundwater soil cleanup values. The intent of the Protection of Groundwater SSLs is to ensure that residual soil contamination remaining at a facility that obtains a No Further-Action determination will Not cause contamination of ground water at levels that will exceed established State ground water standards.
It is possible for a Facility and/or their consultant to work with division staff to use “lines of evidence” and “professional judgment” to show why the exceedance of the Protection of Ground Water SSL will not cause any long-term concerns at the Facility. For example, a Facility may be eligible for a No-Further-Action determination if soil sample data shows that there are multiple intervals of “clean” soil between the soil exceeding the Protection of Groundwater SSLs and the ground water table/saturated zone.