§ 250.305. MSCs for soil.
(a) A person shall implement a remedy under the Statewide health standard that is protective of human health and the environment.
(b) The MSCs for regulated substances in soil are presented in Appendix A, Tables 3 and 4. The methodology for calculating MSCs in soil is detailed in subsections (c)—(e) and the MSCs are further limited to not exceed the physical capacity of the soil to contain a regulated substance. This physical limitation is based on an assumed porosity of 0.35, an assumed dry bulk density of soil of 1.8 kilograms per liter and an assumed density of a regulated substance of 1.0 kilograms per liter. This is calculated according to the equation in paragraph (1). For regulated substances which are organics and liquids at standard temperature and pressure (STP) as identified in Appendix A, Table 5 (Chemical Properties), the physical limitation is further limited based on residual saturation with the additional assumption of a residual saturation ratio of substance volume to soil volume of 0.051, as calculated in Equation (2).
where: ρrs = density of the regulated substance = 1.0 kg/L n = porosity of the soil = 0.35 ρB = dry bulk density of the soil = 1.8 kg/L Sr = residual saturation ratio (substance vol./soil vol.) = 0.051
(c) For the residential standard, the MSC for regulated substances contained in soil is one of the following:
(1) The lowest of the following:
(i) The ingestion numeric value throughout the soil column to a depth of up to 15 feet from the existing ground surface as determined by the methodology in § 250.306 (relating to ingestion numeric values), using the appropriate default residential exposure assumptions contained in § 250.306(d).
(ii) The inhalation numeric value throughout the soil column to a depth of up to 15 feet in soil from the existing ground surface, which considers volatilization into the outdoor air and inhalation of particulates, as determined by the methodology in § 250.307 (relating to inhalation numeric values), using the appropriate default residential exposure assumptions contained in § 250.307(d).
(iii) The soil-to-groundwater pathway numeric value throughout the entire soil column as determined by the methodology in § 250.308 (relating to soil to groundwater pathway numeric values).
(2) The lowest of paragraph (1)(i) and (ii) and, in addition, one of the following:
(i) A demonstration of the soil-to-groundwater pathway soil buffer as identified in § 250.308(b), if applicable.
(ii) A soil-to-groundwater pathway equivalency demonstration as identified in § 250.308(d).
(d) For the nonresidential standard, the MSC for regulated substances contained in soil throughout the soil column to a depth of 2 feet from the existing ground surface is one of the following:
(1) The lowest of the following:
(i) The ingestion numeric value as determined by the methodology in § 250.306, using the appropriate default nonresidential exposure assumptions contained in § 250.306(e).
(ii) The inhalation numeric value which is the lower of the values for volatilization into the outdoor air and the inhalation of particulates, as determined by the methodology in § 250.307, using the appropriate default nonresidential exposure assumptions contained in § 250.307(d).
(iii) The soil-to-groundwater pathway numeric value throughout the entire soil column as determined by the methodology in § 250.308.
(2) The lowest of paragraph (1)(i) or (ii) and, in addition, one of the following:
(i) A demonstration of the soil-to-groundwater pathway soil buffer as identified in § 250.308(b), if applicable.
(ii) A soil-to-groundwater pathway equivalency demonstration as identified in § 250.308(d).
(e) For the nonresidential standard, the MSC for regulated substances contained in soils at depths greater than 2 feet through 15 feet from the existing ground surface, is one of the following:
(1) The lowest of the following:
(i) The inhalation numeric value which considers volatilization to the outdoor air, as determined by the methodology in § 250.307, using the appropriate default nonresidential exposure assumptions contained in § 250.307(d), and using a transfer factor (TF) based upon the calculated emission rate from subsurface soil as specified in the method of Jury, et al. 1990. Water Resources Research, Vol. 26, No. 1, pp. 13—20.
(ii) The soil-to-groundwater pathway numeric value throughout the entire soil column as determined by the methodology in § 250.308.
(2) The value identified in paragraph (1)(i) and one of the following:
(i) A demonstration of the soil-to-groundwater pathway soil buffer as identified in § 250.308(b), if applicable.
(ii) A soil-to-groundwater pathway equivalency demonstration as identified in § 250.308(d).
(f) The MSC for regulated substances contained in soil at depths greater than 15 feet is one of the following:
(i) The soil-to-groundwater pathway numeric value as determined by § 250.308(a).
(ii) A demonstration of the soil-to-groundwater pathway soil buffer as identified in § 250.308(b), if applicable.
(iii) A soil-to-groundwater pathway equivalency demonstration as identified in § 250.308(d).
(g) A person conducting a remediation of soils contaminated with one or more substances having a secondary MCL, but no toxicological properties listed in Appendix A, Table 5B, will not be required to comply with either the direct contact pathway or the soil-to-groundwater pathway requirements for those substances. The substances shall be subject to the requirements of § 250.311(a) through (f) (relating to evaluation of ecological receptors) with respect to evaluation of ecological receptors.
Authority The provisions of this § 250.305 amended under sections 104(a) and 303(a) of the Land Recycling and Environmental Remediation Standards Act (35 P.S. § § 6026.104(a) and 6026.303(a)); and section 1920-A of The Administrative Code of 1929 (71 P.S. § 510-20).
Source The provisions of this § 250.305 amended November 19, 2021, effective November 20, 2021, 51 Pa.B. 7173. Immediately preceding text appears at serial pages (382766) to (382768).
Cross References This section cited in 25 Pa. Code § 250.302 (relating to point of compliance); 25 Pa. Code § 250.311 (relating to evaluation of ecological receptors); 25 Pa. Code § 271.1 (relating to definitions); and 25 Pa. Code § 287.1 (relating to definitions).
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