CLARC data tables and other technical information

Cautions on using CLARC

The requirements and procedures for establishing cleanup levels that are protective of human health and the environment are specified in Washington's Cleanup Rule, Chapter 173-340 WAC. Using data in the CLARC tables may not be sufficient to establish cleanup levels under this regulation.

Using formula values as cleanup levels

The formula values pre-calculated under standard Method B and C and provided in CLARC are not cleanup levels. For example, the formula values do not account for:

• Applicable state and federal laws (for all media)
• Surface water impacts (for groundwater)
• Ecological impacts (for surface water and soil)
• Residual saturation limit for protection of groundwater (for soil)
• Vapor pathway (for soil and groundwater)
• Lower explosive limit limitation (for air)
• Natural background concentrations (for all media)
• Practical quantitation limit (for all media)
• NAPL (non-aqueous phase liquids) limitation (for surface water and groundwater)
• Total site cancer risk and hazard index (for all media)

Ecology may also establish cleanup levels that are more stringent than those required under the applicable method when we determine, 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; see Equation 740-3 in WAC 173-340-740). CLARC does not provide pre-calculated standard Method B or C formula values for petroleum mixtures because it requires special analysis to determine the types of petroleum fractions present at the site — see Table 830-1 in WAC 173-340-900).

For hazardous substances other than petroleum mixtures, the standard Method B and C formula values are based on ingestion only, and CLARC does provide pre-calculated values for those substances. Evaluation of concurrent exposure (ingestion and dermal contact) for hazardous substances other than petroleum mixtures is only required under modified Method B and C, and then only under certain specified circumstances (see Equations 740-4 and -5 in WAC 173-340-740). CLARC does not provide pre-calculated modified Method B or C formula values.

You can look for a chemical in CLARC using its CAS number, which is a registry number assigned by the Chemical Abstracts Service. A chemical substance may have many different names but most have only one CAS number. Numbers in CLARC that begin with "E" are EPA identification numbers and are used due to the lack of a CAS number. The following substances do not have CAS numbers and a temporary CAS has been assigned in CLARC. 

Sources of toxicity values

Sources of cancer toxicity data that include a mutagenic mode of action are highlighted in a orange/dotted pattern (see Source-M). The source of each toxicity value is listed in the Excel and PDF files using the following abbreviations:

• Source-M (e.g., I-M, I-P, etc.) = Chemical is evaluated based on a mutagenic mode of action for early life exposure (highlighted in orange/dotted pattern with bold text). With the exception of vinyl chloride, age-dependent adjustment factors (ADAFs) were used in the cleanup level calculation.
• I = IRIS (Integrated Risk Information System) database from the Environmental Protection Agency (EPA)
• P = PPRTV = Provisional Peer-Reviewed Toxicity Values from EPA's Superfund Health Risk Technical Support Center (STSC). (STSC is within EPA's Office of Research and Development's (ORD's) Center for Public Health and Environmental Assessment, formerly known as the National Center for Environmental Assessment [NCEA]).
• X = PPRTV Screening Level (does not meet all of requirements for a standard PPRTV value)
• A = ATSDR = Agency for Toxic Substances and Disease Registry
• C = Cal EPA = California Environmental Protection Agency
• D = EPA Office of Water
• G = See EPA's Regional Screening Level Users Guide
• H = HEAST = Health Effects Assessment Summary Table from EPA
• O = EPA Office of Pesticide Programs (OPP)
• R = EPA Office of Research and Development (ORD), Center for Public Health and Environmental Assessment (CPHEA). ORD CPHEA is formerly known as NCEA.
• S = Other State sources

Note: The oral cancer potency factor (CPF) for ethylbenzene and naphthalene from Cal EPA, and the inhalation unit risk for ethylbenzene from Cal EPA, have not been included in CLARC pending further evaluation.

Sources for natural background concentrations for metals by geographic area in Washington state

• Regulation WAC 173-340-709: Methods for defining background concentrations
• Natural background soil metals concentrations (Ecology Publication No. 94-115)
• Summary table compiled from Natural Background Soil Metals Concentrations in Washington State (1994).

• Hazardous substances with chemical-specific considerations. For some hazardous substances, potential default cleanup levels may require special calculations or consideration of site-specific factors. Examples include benzo[a]pyrene/cPAHs, and hardness-dependent metals criteria for applicable state and federal fresh surface water laws. Many of these hazardous substances are listed in the CLARC tables with CAPITAL LETTERS and gray-shaded cells. A column (Links to Important Notes) is included in the table, which contains links to relevant information. Many of the links go to a worksheet in this spreadsheet labeled "Notes — Chemical-Specific," while other links go to individual PDF documents.

• Soil to groundwater cleanup level calculations. For default calculation of soil cleanup levels to protect groundwater, use Henry's law constants at 13° Celsius. We used data from ORNL RAIS (i.e., boiling point, critical temperature, enthalpy of vaporization) and formulas in EPA's Vapor Intrusion Screening Level (VISL) Excel spreadsheet system (Chem Props worksheet) to adjust Henry's law based on 25° Celsius to 13° Celsius. If chemical-specific data is not available to derive a Henry’s law constant at 13° Celsius, the Henry’s law constant at 25° Celsius is used in the calculation, if available. Soil protective of groundwater levels are provided for organics that have a Kd value, but no Henry's law constant in CLARC. A Henry's law value of zero was conservatively used for vadose zone soil to make the calculation. It's noted that chemical loss due to volatilization based on Henry's law is not a major driver in the 3-phase partitioning model. A Henry’s Law constant is not needed to calculate soil protective of groundwater cleanup levels for saturated zone soil since the default air-filled soil porosity is assumed to be zero.

• Inhalation Toxicity Criteria. IRIS and other Ecology sources of toxicity data identify the inhalation reference concentration (RfC) and inhalation unit risk (IUR), and do not present conversions to an inhalation RfD (RfDi) or inhalation cancer potency factor (CPFi). For calculating cleanup levels based on inhalation exposure, MTCA expresses inhalation toxicity data as an inhaled dose or intake expressed as an RfDi or a CPFi — based on adjustments for body weight (70 kilograms) and breathing rate (20 m³/day). The conversion formulas are presented below:

  • Inhalation RfC to RfDi - RfDi (mg/kg-day) = (RfC [mg/m³] ÷ 70 kg) x 20 m³/day

  • Inhalation URF (IUR) to CPFi - CPFi (kg-day/mg) = (IUR [m³/µg] x 70 kg) ÷ (20 m³/day x 0.001 mg/µg)

• Rounding. Cleanup levels are rounded to two significant figures. Values other than cleanup levels (such as toxicity values and other parameters used to calculate cleanup levels) may have more than two significant figures. For example, in making media transfer calculations such as estimating soil concentrations protective of groundwater, or estimating concentrations in groundwater or soil gas that are protective of indoor air, the full calculated risk-based value for the target concentration (in groundwater or indoor air) is used in the calculation. The final value in the media-transfer calculation is rounded to two significant figures.

• CLARC Database Name Range. The CLARC Master Table database is defined by the name range "clarc" (cells A2 through CN667). Columns A through CN are numbered on Excel Row 669 from 1 to 92 in the CLARC Master Table. Users may use lookup functions in Excel (e.g., VLOOKUP) when you need to bring in information from CLARC to investigation report tables that contain chemical specific information at your site. Note that your table needs to contain the chemical CAS number because it's the lookup value for the name range "clarc". For example, you could look up a soil Method B noncancer human health based cleanup level for a chemical at your site by its CAS number. VLOOKUP instructions and an example are provided in a separate worksheet at the end of the CLARC Master Table Workbook.

• History of Changes to CLARC. The change history is provided in a downloadable pdf document.