SECTION 350.71. General Requirements

(a) This subchapter describes separate tiered processes for establishing protective concentration levels of COCs that can remain in the source medium and be protective of human and ecological receptors at the point of exposure within the exposure medium. The tiered process for the calculation of human health protective concentration levels (PCLs) is set forth in §350.75 of this title (relating to Tiered Human Health Protective Concentration Level Evaluation) and is structured conceptually in terms of Tiers 1, 2, and 3. Each tier sets forth conditions to calculate PCLs and each successive tier incrementally provides for more consideration of site-specificity and sophistication in the PCL calculation process. The person can move through the tiered process or start at any tier, but must conduct the cumulative check in accordance with §350.72(b) of this title (relating to Carcinogenic Risk Levels and Hazard Indices for Human Health Exposure Pathways). The human health PCLs under Tiers 1, 2 and 3 are set based on the receptors and exposure pathways as specified in subsections (b) and (c) of this section in consideration of the land use classification of the affected property, the classification of groundwater, the distribution of COCs in environmental media, and the presence of receptors. The tiered process for ecological evaluations is different. Tier 1 is an exclusion criteria checklist that is used to exclude sites which do not pose potential ecological risk from further evaluation. If a site is not excluded from Tier 1, then the person must further evaluate the site for ecological risk, and possibly establish ecological PCLs are under Tiers 2 or 3. The lowest of the human health and any applicable ecological PCLs determined for each COC for the soil, groundwater, surface water, sediment, or air as required, and are then respectively compared with representative concentrations of COCs in the soil, groundwater, surface water, sediment, or air as appropriate to determine if the PCLs are exceeded or not. If PCLs are exceeded for certain COCs, then PCLs may be further evaluated under the respective tiered process and compared again to representative site concentrations to determine if further action is needed; otherwise a response action must be initiated. No further action is required for those COCs which do not exceed the PCLs, and the cumulative criteria of §350.72(b) of this title.

(b) The person shall:

(1) ensure PCLs are protective of human health and the environment;

(2) determine human health PCLs based on residential or commercial/industrial exposure as appropriate for the land use of each affected on-site and off-site property;

(3) assume the human receptor is a resident for residential property; and

(4) assume the human receptor is a commercial/industrial worker for commercial/industrial property.

(c) The person shall develop PCLs for each of the following human health exposure pathways which are complete or reasonably anticipated to be completed based on the provided criteria.

(1) Ingestion of COCs in class 1 or 2 groundwater. The person shall consider the ingestion of COCs in class 1 or 2 groundwater to be a complete or reasonably anticipated to be completed exposure pathway when class 1 or 2 groundwater is affected.

(2) COCs in class 3 groundwater. The person shall establish PCLs for class 3 groundwater as necessary to protect human health and safety, and the environment, and to comply with the groundwater response objectives in accordance with Subchapter B of this chapter (relating to Remedy Standards).

(3) Inhalation of volatile emissions in outdoor air from COCs in groundwater-bearing units. The person shall at a minimum consider this to be a complete or reasonably anticipated to be completed exposure pathway when a plume management zone is established in accordance with §350.33(f) of this title (relating to Remedy Standard B) unless the person:

(A) demonstrates with representative and appropriate vapor monitoring data or other technically appropriate method that volatile emissions from groundwater are protective; or

(B) otherwise demonstrates that the pathway is incomplete at the affected property. A competent, existing physical control which prevents the release of COCs from groundwater into air above the PCLs may be considered in accordance with subsection (d) of this section.

(4) Combined inhalation of volatile emissions and particulates from COCs in surface soil, dermal contact with COCs in surface soil, ingestion of COCs in surface soil, and for affected residential properties, ingestion of above and below-ground vegetables grown in surface soils containing COCs. Other than within a waste control unit, the person shall consider this combined exposure pathway to be a complete or reasonably anticipated to be completed exposure pathway; however, competent existing physical controls may be considered in accordance with subsection (d) of this section.

(5) Leaching of COCs in surface and subsurface soils to groundwater. The person shall consider this to be a complete or reasonably anticipated to be completed exposure pathway; however, a competent existing physical control which prevents the release of COCs from soils to groundwater above the PCLs may be considered in accordance with subsection (d) of this section.

(6) Inhalation of volatile emissions from COCs in subsurface soils. Other than below a waste control unit, the person shall consider this to be a complete or reasonably anticipated to be completed exposure pathway unless the person demonstrates with representative and appropriate vapor monitoring data, or other technically appropriate method that the exposure pathway is incomplete. A competent existing physical control which prevents the release of COCs from subsurface soils to air above the PCLs may be considered in accordance with subsection (d) of this section.

(7) Contact with surface water or sediment containing COCs originating from the source area. The person shall evaluate this exposure pathway to determine if it is a complete or reasonably anticipated to be completed exposure pathway when a COC has been discharged or will discharge to a surface water body or sediment.

(8) Other complete or reasonably anticipated to be completed exposure pathways. The person shall reasonably evaluate other potentially applicable exposure pathways and identify the ones which are complete or are reasonably anticipated to be completed.

(d) In accordance with subsection (c)(3) - (6) of this section, and §350.77 of this title (relating to Ecological Risk Assessment and Development of Ecological Protective Concentration Levels), the presence of a competent existing physical control which prevents the exposure of receptors to COCs may be considered as sufficient proof that the exposure pathway is incomplete for the geographic area covered by the control when the person is able and willing to incorporate that physical control as a Remedy Standard B response action meeting all associated performance, institutional control, and post-response action care requirements, including financial assurance, for that physical control. The existing physical control shall not be considered to be a remedy for or remove the exposure pathway from consideration for the geographic area which extends beyond the existing limits of the competent existing physical control. Consideration of physical controls during the exposure pathway analysis does not negate or otherwise supercede the soil or groundwater response objectives as set forth in Subchapter B of this chapter (relating to Remedy Standards).

(e) The person shall establish the human health POE(s) for each environmental media in accordance with §350.37 of this title (relating to Human Health Points of Exposure). Consideration of physical controls during the exposure pathway analysis does not negate or otherwise supercede the POE criteria of §350.37 of this title.

(f) The person shall establish the risk-based exposure limits in accordance with §350.74 of this title (relating to Development of Risk-Based Exposure Limits) when establishing PCLs.

(g) For COCs which have both carcinogenic and noncarcinogenic effects for an exposure pathway, the person shall establish separate PCLs for both carcinogenic and noncarcinogenic effects for the individual and combined exposure pathways. The person shall then use the lower of the carcinogenic or noncarcinogenic PCL for that COC and exposure pathway.

(h) The person shall ensure that PCLs developed are protective for both on-site and off-site human receptors at the carcinogenic risk levels and hazard quotient and index as specified in §350.72 of this title (relating to Carcinogenic Risk Levels and Hazard Indices for Human Health Exposure Pathways), as well as for applicable ecological receptors.

(i) The person shall establish critical PCLs in accordance with §350.78 of this title (relating to Determination of Critical Protective Concentration Levels).

(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.

Source Note: The provisions of this §350.71 adopted to be effective September 23, 1999, 24 TexReg 7436; amended to be effective March 19, 2007, 32 TexReg 1526