Colorado
Air, water and soil remedial objectives
Colorado air, water and soil remedial objectives
The Hazardous Materials and Waste Management Division of the Colorado Department of Public Health and Environment (CDPHE) says it now exclusively uses the U.S. Environmental Protection Agency's Regional Screening Levels (RSLs) as its cleanup levels and screening levels for all environmental media except water. For water, the RSLs are secondary to Regulation 41 of the Water Quality Control Division.
In a Phase I ESA
ASTM E1527-21 does not name cleanup or screening levels among its standard record sources. They are the yardstick for the sample results in a CDPHE file, and for judging what an old closure was measured against.
CDPHE points to the most recent RSL Summary Table calculated at a target cancer risk of one in a million and a target hazard quotient of 1.0, and says which columns it uses for what.
| Question | Columns CDPHE says it uses |
|---|---|
| Indoor air | The Resident Air and Industrial Air columns, to judge whether indoor air results show a potential human health impact by the air pathway |
| Soil | The Resident Soil and Industrial Soil columns, as screening levels for whether soil contamination warrants further investigation or cleanup |
| Soil as a threat to groundwater | The Protection of Groundwater SSLs in the rightmost column of the table, as screening levels protective of groundwater quality in Colorado |
| Surface water and groundwater | The standards and methods of the Colorado Water Quality Control Commission first. RSLs for water may be used when there is no Colorado water standard for a chemical, or in other very specific circumstances |
Three details shape how to read a number in a file.
- Two groundwater protection values can apply. Some constituents have two Protection of Groundwater SSLs, an MCL-based one and a risk-based one. Where groundwater beneath and downgradient of the facility is used for drinking water, or is likely to be, CDPHE says the lower of the two applies. It encourages facilities and their consultants to settle the right value with the division's project manager, so check the file for that decision.
- Arsenic has its own guidance. CDPHE's page links separate risk management guidance for evaluating arsenic concentrations in soil.
- The basis changed. CDPHE's page links a document on its change to the RSLs as the primary remedial objectives for air, soil and groundwater. The page read does not give the date of the change. For an older cleanup, check which values the closure used.
These objectives are CDPHE's. Petroleum tank releases are measured against another agency's tiered criteria; see Petroleum release closure criteria. Closure with groundwater still above state standards is on the Conditional closures page.
Where to read the rule and the numbers
CDPHE's Air, water and soil remedial objectives page links EPA's RSL generic tables and the Water Quality Control Commission's regulations. This handbook does not carry the numbers.
Getting the file
The pages read name no file of their own for these objectives. For the decision at one site, the division takes records requests through the form on its records review page or at cdphe_cora_hmwmd@state.co.us.
Sources
Colorado Department of Public Health and Environment pages, read October 7, 2026, no modified date shown: