Cleanup Levels and Risk Calculation (CLARC)
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Please read the information contained in 'Cautions and Limitations' before navigating this site.

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Cautions and Limitations

History of Changes

CLARC Release Notes

Welcome to CLARC

Welcome to the Cleanup Levels and Risk Calculation (CLARC) web site. Here you’ll find information to help establish cleanup levels for hazardous waste sites to comply with the Model Toxics Control Act (MTCA) Cleanup Regulation, chapter 173-340 WAC. This site is developed and maintained by the Washington State Department of Ecology (Ecology).

All information can be accessed from the Table of Contents  or from the drop-down menus above. A few of the more important links are available to the left.

August 2015 Updates:

  • 1. Soil Cleanup Levels Protective of Groundwater:

    We now include soil cleanup levels protective of groundwater for many chemicals, calculated with the “fixed parameter three-phase partitioning model” (described in WAC 173-340-747(4) and based on MTCA Equation 747-1). These are available in the CLARC Master Table in the “Soil Methods B & A unrestricted” tab and in the Soil – Method B and Method A (unrestricted land use)” PDF. A guidance document describing the Soil-to-Groundwater pathway and the derivation of the pre-calculated cleanup levels is available here, as well as from the guidance links at the top of the columns within the Excel and PDF documents and from the Guidance drop-down menu at the top of this page (Guidance→ Soil Cleanup Standards – Protection of Groundwater→ Guidance for Soil Protective of Groundwater).

  • 2. Vapor Intrusion Screening Level Table:

    Vapor intrusion screening levels are now included in the CLARC Master Table and in separate PDF files with links on the CLARC Data Tables page. These are revisions of Table B-1 from Ecology’s draft 2009 document, “Guidance for Evaluating Soil Vapor Intrusion in Washington State: Investigation and Remedial Action."

    A summary of the changes since 2009 is available here.

  • 3. Toxicity Value Updates:

    Toxicity values in CLARC for the following hazardous substances have been changed to be consistent with those in EPA’s Regional Screening Level Tables:

    • Direct black 38 (CAS 1937-37-7)
    • Direct blue 6 (CAS 2602-46-2)
    • Direct brown 95 (CAS 16071-86-6)
    • Ethyl acrylate (CAS 140-88-5)

    The changes to toxicity values affect some of the calculated Methods B and C cleanup levels for these substances.

    Also, the inhalation reference dose was deleted for dichloroethylene; 1,2-trans (CAS 156-60-5).

  • 4. Corrections to Groundwater Cleanup Levels:
    • Copper (CAS 7440-50-8)- calculated Method B (changed from 320 µg/L to 640 µg/L)
    • Copper (CAS 7440-50-8) - calculated Method C (changed from 700 µg/L to 1400 µg/L)
    • Arsenic, inorganic (CAS 7440-38-2) - Washington State Maximum Contaminant Level (changed from 100 µg/L to 10 µg/L)
    • Bromodichloromethane (CAS 75-27-4) - Washington State Maximum Contaminant Level (changed from 0.08 to 80 µg/L)
    • Chlorine (CAS 7782-50-5) - Washington State Maximum Contaminant Level (changed from 4 µg/L to 4000 µg/L)
    • Chlorine Dioxide (CAS 10049-04-4) - Washington State Maximum Contaminant Level (changed from 80 µg/L to 800 µg/L)
    • Ethylbenzene (CAS 100-41-4) - Washington State Maximum Contaminant Level (changed from 70 µg/L to 700 µg/L)
    • Glyphosate (CAS 1071-83-6) - Washington State Maximum Contaminant Level (changed from 70 µg/L to 700 µg/L)

  • 5. Updates to the Trichloroethylene Guidance Document:

    The cleanup levels and toxicity values have not changed. Parts of the guidance document were revised to provide clarification about the derivation of the cleanup levels. The document is available here and from the Guidance drop-down menu at the top of this page (Guidance→ Toxicological Information submenu→ TCE and PCE).

  • 6. National Recommended Water Quality Criteria:

    Changes to the National Recommended Water Quality Criteria, published by EPA in June, 2015, have not been incorporated into the CLARC Surface Water tables at this time.

May 2014 Changes: We have made significant changes to this web site, with more planned for the future.

The searchable chemical substance database has been disabled.

To find information:

  • Cleanup level information is now contained in an Excel spreadsheet and pdf files. These are accessed here or from the “CLARC Data Tables” link on the left side of the page. The files contain Methods A, B, and C cleanup levels, Applicable or Relevant and Appropriate Requirements (ARARs), toxicity values, and physical parameters.
  • The drop-down menus at the top of the page provide access to information about MTCA, guidance for determining cleanup levels, and tools to help set cleanup standards. There are no significant changes from the previous version of CLARC.
  • Future plans include the addition of simplified cleanup level calculations for the soil-to-groundwater pathway, the vapor intrusion pathway, and terrestrial ecological evaluation.

We have:

  • Updated many toxicity values to be consistent with EPA’s November 2013 Regional Screening Level (RSL) tables. See the “History of Changes” for a summary. The list of hazardous substances in CLARC is unchanged.
  • Expanded the sources of toxicity values to include those from the California Environmental Protection Agency (Cal-EPA) and the Agency for Toxic Substances and Disease Registry (ATSDR). However, the New Jersey Department of Environmental protection oral slope factor for chromium (VI) and the Cal-EPA oral and inhalation cancer potency factors for ethylbenzene are not included pending further evaluation.
  • Added Inhalation Correction Factors for chemicals that did not previously have them. This allows the calculation of Method B and Method C groundwater cleanup levels for additional chemicals.

Caution: The use of CLARC alone is not sufficient to establish cleanup levels under the MTCA Cleanup Regulation, chapter 173-340 WAC. Please refer to 'Cautions and Limitations' before using CLARC to develop cleanup levels. The “Guidance” dropdown menu (above) contains links to information about selecting cleanup levels. It also links to important information about toxicity and cleanup levels for 3 chemicals: tetrachloroethylene, trichloroethylene and vinyl chloride.

If you have questions or need assistance please contact Jim White.

Disclaimer: CLARC is not mandated by law, but rather is provided as a service to staff and the public. While the information provided in CLARC is extensive, it is not exhaustive and the user may need to obtain information from additional sources for certain hazardous substances. Although CLARC has undergone review to ensure the quality of the information provided, there is no assurance