§ 250.604. Fate and transport modeling requirements for exposure assessments.
(a) A person may use the soil-to-groundwater model in § 250.308(a)(2) (relating to soil to groundwater pathway numeric values) to estimate site-specific, soil-to-groundwater leaching potential for organic contaminants if the following conditions are met:
(1) Site-specific values of water-filled soil porosity, dry soil bulk density, dilution factors (DF) and fraction organic carbon in soil beneath the source of contamination (that is, not from top soil) are appropriately justified and the person provides supporting data to the Department.
(2) Koc values as provided in § 250.308(a)(2) are used or site-specific values which are appropriately justified are used and the person provides supporting data to the Department.
(3) There is no identified separate phase liquid contamination at the site.
(4) Other processes such as colloidal transport or transport by means of dissolved organic matter (DOM) are not significant at the site.
(5) The application of the soil-to-groundwater model shall meet the most current EPA or ASTM quality assurance/quality control criteria approved by the Department.
(b) Except for the soil-to-groundwater model in § 250.308(a)(2), a person planning to use other fate and transport models and methods to estimate exposure concentrations and to develop site-specific standards shall use appropriate models or methods approved by the Department. The application of groundwater models shall meet the most current EPA or ASTM quality assurance/quality control criteria approved by the Department.
Cross References This section cited in 25 Pa. Code § 250.602 (relating to risk assessment procedures); and 25 Pa. Code § 250.606 (relating to development of site-specific standards).
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