| (j) The person is not required to combine exposure pathways across source media (e.g., soil exposure pathways combined with groundwater exposure pathways) unless the executive director determines such combination is necessary to address actual situations where receptors are simultaneously exposed to COCs present in multiple source media. (k) For Tiers 1, 2, and 3 as explained in §350.75 of this title (relating to Tiered Human Health Protective Concentration Level Evaluation) and §350.77 of this title (relating to Ecological Risk Assessment and Development of Ecological Protective Concentration Levels), the person shall establish PCLs for each individual COC within each environmental medium unless the conditions of paragraphs (1), (2), (3), or (4) of this subsection are met or unless the use of paragraphs (1), (2), (3), or (4) of this subsection is prohibited by the individual program area listed in §350.2 of this title (relating to Applicability). For the purposes of determining whether a COC meets the conditions of paragraphs (1), (2), (3), or (4) of this subsection, a COC should be considered detected in a particular environmental medium if the analytical measurement is greater than the method detection limit and the analytical response meets the qualitative identification criteria recommended in the analytical method. (1) The COC is detected in at least one sample, but all detected COC concentrations and sample detection limits for the COC are less than the residential assessment level in the environmental medium being evaluated under this paragraph, as well as in all other environmental media from which samples were collected. (2) The COC is detected in at least one sample in the environmental medium, but the conditions described in one of subparagraphs (A) - (E) of this paragraph are met and all nondetected results for the COC are less than the residential assessment level in the environmental medium being evaluated under this paragraph. (A) The COC meets all of the conditions in the following clauses (i) - (iii) of this subparagraph: (i) twenty or more representative samples analyzed for that COC have been collected from the environmental medium evaluated under this subparagraph; (ii) the COC is detected in less than 5% of the twenty or more samples required in clause (i) of this subparagraph; and (iii) the executive director determines that a PCL is not warranted for the COC in order to protect human health and the environment in consideration of, but not limited to, the concentration and distribution of the COC in environmental media, source area information, knowledge of on-site historical operations, characteristics of the COC and the affected property, and companion and daughter product relationships to the COC. (B) The COC is a common laboratory contaminant (i.e., methylene chloride, acetone, toluene, 2-butanone (methyl ethyl ketone), dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, butylbenzyl phthalate, bis (2-ethylhexyl) phthalate, and di-n-octyl phthalate), and the concentration of the COC detected in each sample for that environmental medium does not exceed 10 times the maximum amount detected in any associated blank, and the COC is not anticipated to be present based on knowledge of on-site historical operations including consideration of companion and daughter products. (C) The COC is not a common laboratory contaminant, as defined in subparagraph (B) of this paragraph, and the concentration of the COC detected in each sample for that environmental medium does not exceed five times the maximum amount detected in any associated blank, and the COC is not anticipated to be present based on knowledge of on-site historical operations including consideration of companion and daughter products. (D) The maximum concentration of the COC detected at the affected property does not exceed the property-specific or Texas-specific background concentration as specified in Figure: 30 TAC §350.51(m). For the purpose of determining whether the COC meets the conditions of this paragraph, the person shall consider the maximum concentration of the COC to be the higher of the maximum detected concentration or the appropriate proxy value as determined in accordance with §350.51(n) of this title (relating to Affected Property Assessment). (E) The person sufficiently demonstrates that the release of COCs did not result from activity at the on-site property based on appropriate evidence, including, but not limited to, the concentration and distribution of the COC in environmental media, source area information, consideration of companion and daughter products, and knowledge of on-site historical operations. (3) The COC is known or is reasonably anticipated to be associated with historical or current activities conducted at the on-site property, but the COC is not detected in any sample in the environmental medium, and all sample detection limits for the COC are less than the residential assessment level for the environmental medium. (4) The COC is not known or is not reasonably anticipated to be associated with historical or current activities conducted at the on-site property, and is not detected in any sample in the environmental medium. |
