CLARC guidance

Model Toxics Control Act

• MTCA statute Chapter 70A.305 RCW (formerly Chapter 70.105D RCW) 
• MTCA regulation (also called the MTCA Cleanup Rule): Chapter 173-340 WAC
• MTCA regulation and statute (Ecology Publication No. 94-06)
• Process for cleanup of hazardous waste sites (Ecology Publication No. F-TC-94-129)
• Focus on Washington's environmental cleanup law (Ecology Publication No. F-TC-94-130)
• Concise explanatory statement for amendments to MTCA cleanup regulation (2001) (Ecology Publication No. 01-09-043)
• Model Toxics Control Act webpage

Cleanup standards - General

• Overview of cleanup standards, WAC 173-340-700 through 710

Mixing cleanup methods A, B, C

• Guidance on the use of Method A, B, and C cleanup levels and mixing methods (CLARC guidance) 

Soil cleanup standards — general

• Regulation: WAC 173-340-740 (unrestricted land use)
• Regulation: WAC 173-340-745 (industrial properties)
• Developing soil cleanup standards under MTCA (Publication No. 01-09-071)
• Equations and default exposure parameter values (WAC 173-340-740 & 745)

Method A soil cleanup levels

• Unrestricted land use (search Table 740-1 in WAC 173-340-900)
• Industrial land use (search Table 745-1 in WAC 173-340-900)

Soil cleanup standards — Protection of environment

• Regulation: WAC 173-340-7490 through -7494
• Terrestrial Ecological Evaluations webpage
• Terrestrial ecological evaluation process: draft technical document (Publication No. 19-09-051)

Terrestrial ecological screening values

• Simplified Evaluation (search Table 749-2 in WAC 173-340-900)
• Site-Specific Evaluation (search Table 749-3 in WAC 173-340-900)

Soil cleanup standards — Protection of groundwater

• Regulation: WAC 173-340-747
• Soil cleanup levels to protect groundwater (CLARC guidance)
• Partitioning model equations and default hydrogeologic parameter values (2001)
• Calculation tool for single chemicals (MTCASGL Ver. 12.0)

Method A table values (background for developing tables in WAC 173-340-900)

• Soil - Unrestricted land use (background for Table 740-1) (2001 & 2004)
• Soil - Industrial land use (background for Table 745-1) (2001 & 2004)
• Concise explanatory statement for the amendments to the Model Toxics Control Act (MTCA) Cleanup Regulation (2001)

 Method B and C formula values

• Formula values for potable groundwater, surface water, air, and soil (2001)

Groundwater cleanup standards

• Regulation: WAC 173-340-720
• Developing ground water cleanup standards under MTCA (Publication No. 01-09-049)
• Equations and default exposure parameter values (WAC 173-340-720)
• Method A groundwater cleanup levels (search Table 720-1 in WAC 173-340-900)

Method A table values (background for developing tables in WAC 173-340-900)

• Potable groundwater (background for Table 720-1) (2001 & 2004) 

Method B and C formula values

• Formula values for potable groundwater, surface water, air, and soil (2001)
• Calculation tool for single chemicals (MTCASGL Ver. 12.0)

Concentrations established under ARARs

• Applicable state & federal laws: potable groundwater

Surface water cleanup standards

• Regulation: WAC 173-340-730
• Developing surface water cleanup standards under MTCA (Publication No. 01-09-050)
• Equations and default exposure parameter values (WAC 173-340-730)

Method B and C formula values

• Formula values for potable groundwater, surface water, air, and soil (2001)

Concentrations established under ARARs

• Applicable state & federal laws: surface water–protection of human health
• Applicable state & federal laws: surface water–protection of environment

Air cleanup standards

• Regulation: WAC 173-340-750
• Developing air cleanup standards under MTCA (Publication No. 01-09-072)
• Equations and default exposure parameter values (WAC 173-340-750)

Method B and C formula values

• Formula values for potable groundwater, surface water, air, and soil (2001)

• Ecology's petroleum cleanup webpage
• Toxicity data and physical/chemical properties for petroleum mixtures (July 2024)
• Calculation of Method B and Method C cleanup levels for petroleum mixtures (Nov. 2023)

• Ecology's vapor intrusion webpage and guidance
• Ecology's vapor intrusion screening levels for commercial workers (CLARC guidance)
• EPA's vapor intrusion webpage

• CLARC historical table summary of chemical-specific considerations (CLARC guidance)
• Benzo(a)pyrene and carcinogenic PAHs (cPAHs): Deriving cleanup levels under MTCA (CLARC guidance)
• Evaluating the human health toxicity of carcinogenic PAHs (cPAHs) using Toxicity Equivalency Factors (TEFs) (Toxics Cleanup Program Implementation Memo No. 10)
• Evaluating the toxicity and assessing the carcinogenic risk of environmental mixtures using Toxicity Equivalency Factors (CLARC guidance)
• Trichloroethylene (TCE): Deriving cleanup levels under MTCA (CLARC guidance)
• Tetrachloroethylene (PCE): Deriving cleanup levels under MTCA (CLARC guidance)
• Vinyl chloride: Deriving cleanup levels under MTCA (CLARC guidance)
• Uranium soluble salts: Noncancer oral reference dose for uranium, soluble salts (CLARC guidance)

• Ecology's terrestrial ecological evaluations (TEE) webpage
• Ecology's draft technical document: Terrestrial Ecological Evaluations under MTCA (Publication No. 09-01-09-051)