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Toxics Cleanup Program Home > CLARC > CLARC Cautions and Limitations

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Cautions and Limitations

History of Changes

CLARC Release Notes

Caution on the Use of CLARC

The requirements and procedures for establishing cleanup levels that are protective of human health and the environment are specified in the MTCA Cleanup Regulation, chapter 173-340 WAC. The use of CLARC is not sufficient to establish cleanup levels under the regulation.

Use of Formula Values as Cleanup Levels
The formula values pre-calculated under standard Method B and C and provided in CLARC are NOT cleanup levels. The formula values DO NOT, for example, account for the following:
  • Consideration of applicable state and federal laws (for all media)
  • Consideration of surface water impacts (for ground water)
  • Consideration of ecological impacts (for surface water and soil)
  • Consideration of the residual saturation limit for protection of ground water (for soil)
  • Consideration of the vapor pathway (for soil)
  • Consideration of the lower explosive limit limitation (for air)
  • Consideration of natural background concentrations (for all media)
  • Consideration of the practical quantitation limit (for all media)
  • Consideration of the NAPL limitation (for surface water and ground water)
  • Consideration of total site risk (for all media)
The department may also establish cleanup levels that are more stringent than those required under the applicable method when the department determines, based on a site-specific evaluation, that such levels are necessary to protect human health and the environment.

Limitations of CLARC

  • Modified Method B and C (Site-Specific Risk Assessment)
CLARC does not provide pre-calculated formula values for modified Method B or C. The calculation of modified Method B or C values requires the use of site-specific and/or chemical-specific values instead of the default values provided in the regulation.
  • Soil – Direct Contact Pathway – Concurrent Exposure (Ingestion and Dermal Contact)
For petroleum mixtures, the standard Method B and C formula values are based on concurrent exposure (ingestion and dermal contact). CLARC does not provide pre-calculated standard Method B or C formula values for petroleum mixtures, including values based on the direct contact pathway (see discussion below).

For hazardous substances other than petroleum mixtures, the standard Method B and C formula values are based on ingestion only. CLARC does provide pre-calculated standard Method B and C formula values for those substances. For hazardous substances other than petroleum mixtures, evaluation of concurrent exposure (ingestion and dermal contact) is only required under modified Method B and C and then only under certain specified circumstances. The regulation provides standard equations and default values for evaluating concurrent exposure. CLARC does not provide pre-calculated Method B or C formula values using those standard equations and default values.

  • Petroleum Mixtures
CLARC does not provide pre-calculated standard Method B or C formula values for petroleum mixtures. The calculation of standard Method B and C formula values for petroleum mixtures depends on the composition of a mixture. The composition must be determined on a site-specific basis.
  • Ammonia
CLARC does not provide pre-calculated standard Method B or C formula values for ammonia. The calculation of standard Method B and C formula values depends on the water quality characteristics (temperature and pH) and the chemical form/species of ammonia (e.g., ionized or non-ionized).
  • Asbestos
CLARC does not provide pre-calculated standard Method B or C formula values for asbestos. The calculation of standard Method B and C formula values depends on the fiber type and content. Note that the metric for asbestos is based on fiber type and is usually expressed as fibers/L and not as the usual mg/L or ug/L metric.
  • Chromium
CLARC does not provide pre-calculated standard Method B or C formula values for total chromium. CLARC does provide pre-calculated standard Method B and C formula values for chromium III and chromium VI.

Assessors should test for total chromium first and then test for chromium VI only if the concentration for total chromium exceeds the cleanup level for chromium VI.

If chromium VI is present at the site, then the concentration of chromium III is determined by subtracting the chromium VI concentration from the total chromium concentration. · If chromium VI is NOT present at the site, then the site assessor may assume that the measured concentration of total chromium is the concentration of chromium III.

Of course, if there is documented evidence that chromium VI was never used at the site, then the site assessor does not need to test for chromium VI and may assume that the measured concentration of total chromium is the concentration of chromium III.
  • Lead
CLARC does not provide pre-calculated standard Method B or C formula values for lead. Values for lead cannot be calculated using the equations provided in the regulation. Assessors should consult with the Department of Ecology regarding the use of EPA’s Integrated Exposure Uptake Biokinetic (IEUBK) model to calculate soil cleanup levels.
  • Manganese
CLARC provides pre-calculated standard Method B or C formula values for manganese. The formula value for manganese depends on the reference dose (RfD). The reference dose was obtained from the U.S. Environmental Protection Agency’s Integrated Risk Information System (IRIS), but was not modified as recommended by the EPA. The recommended modification depends on the route of exposure. EPA recommends that a modifying factor of "1" should be used when assessing exposure from food and that a modifying factor of "3" should be used when assessing exposure from drinking water or soil. This modification factor is based on the increased exposure of children to manganese-contaminated water and soil. Please consult IRIS for a more complete description of the basis for the modification factors. As noted, the RfD for manganese listed in CLARC and used to pre-calculate the formula values for standard Method B and C has not been adjusted. If the modifying factor of "3" for manganese is used, then the formula values for standard Method B and C for soil and ground water would be one-third the value presented in CLARC.