(a) General requirement. The person shall use the criteria provided in subsections (b) - (j) of this section and the risk-based exposure limit (RBEL) equations provided in the following figures, as applicable, to establish RBELs appropriate for the type of chemical of concern (COC), the complete and reasonably anticipated to be completed exposure pathways, receptors, and land uses. The person shall establish RBELs for carcinogenic COCs and noncarcinogenic COCs using the default exposure factors provided in the following figure for residents and commercial/industrial workers, unless the executive director approves the use of alternate exposure factors in accordance with subsection (j) of this section.
(b) Air inhalation RBEL. The air inhalation RBEL ( Air RBEL Inh ) is the protective concentration of a COC in air at the point of exposure (POE) for human inhalation.
(1) Under Tiers 2 and 3 as described in §350.75 of this title (relating to Tiered Human Health Protective Concentration Level Evaluation), the person may use the lower of available eight-hour time-weighted average occupational inhalation criteria (i.e., Occupational Safety and Health Administration Permissible Exposure Limits, or American Conference of Governmental Industrial Hygienists Threshold Limit Values), as Air RBEL Inh for inhalation pathways for commercial/industrial workers within the limits of affected commercial/industrial properties which have a health and safety plan in place. The health and safety plan shall be designed to ensure compliance with the applicable occupational inhalation criteria and require the monitoring of COC levels in the working air environment, and specify actions that will be taken in the event of exceedance of the occupational inhalation criteria. When occupational inhalation criteria are used, the person shall provide documentation of the health and safety plan, certify that the plan is followed, and demonstrate that the off-site receptors are protected as required by §350.71(h) of this title (relating to General Requirements). The use of occupational inhalation criteria as RBELs shall require the person to comply with the institutional control requirements in §350.111(b) and (b)(14) of this title (relating to Use of Institutional Controls).
(2) The air RBELs may not exceed any other applicable federal or state air quality standards.
(c) Soil dermal contact RBEL. The soil dermal contact RBEL ( Soil RBEL Derm ) is the protective concentration of a COC at the POE in soil based upon direct dermal contact to soil by humans. The soil dermal contact RBEL shall also be based on COC-specific values for dermal absorption fraction (ABS.d) and gastrointestinal absorption fraction (ABS GI ) provided in the following figure, unless the executive director approves the use of alternate ABS.d and ABS GI values in accordance with subsection (j)(1)(A) and (B) of this section. It is not necessary to calculate a soil dermal contact RBEL for COCs with vapor pressure in mm of Hg greater than or equal to 1.
(d) Soil ingestion RBEL. The soil ingestion RBEL ( Soil RBEL Ing ) is protective concentration of a COC at the POE in soil based upon human ingestion.
(e) Vegetable ingestion RBELs. The vegetable RBELs ( AbgVeg RBEL Ing and BgVeg RBEL Ing ) are the protective concentration of a COC in aboveground vegetables and below-ground vegetables, respectively, for ingestion by residents. The person shall establish RBELs for ingestion of aboveground vegetables for all carcinogenic and noncarcinogenic COCs which are metals. In addition, the person shall establish RBELs for ingestion of below-ground vegetables for all carcinogenic and noncarcinogenic COCs with a dimensionless Henry's Law Constant less than 0.03, as shown in the figure in §350.73(f) of this title (relating to Determination and Use of Human Toxicity Factors and Chemical Properties), when either of the following criteria are met:
(1) the COC is a metal; or
(2) the COC has a logarithmic octanol-water partition coefficient (Log K ow ) greater than four as shown in the figure in §350.73(f) of this title ; or
(f) Groundwater ingestion RBEL.
(1) The groundwater ingestion RBEL ( GW RBEL Ing ) is the protective concentration of a COC at the POE in groundwater based upon human ingestion of groundwater. However, if available, the person shall use the lower of the two values established under paragraphs (2) and (3) of this subsection instead.
(2) The person shall use the primary maximum contaminant level (MCL) as provided in 40 Code of Federal Regulations (CFR) Part 141, as amended, or the most currently available federal action level for drinking water (e.g., lead and copper) as the RBEL when available for the COC.
(3) The person shall use the secondary MCLs established for individual COCs as provided in 40 CFR Part 143, as amended, as RBELs, or other scientifically valid published criteria in cases where COCs are present at concentrations which present objectionable characteristics such as taste or odor (e.g., methyl tertiary butyl ether) under the following circumstances:
(g) Class 3 groundwater RBEL. The class 3 groundwater RBEL ( GW RBEL Class 3 ) is the acceptable concentration of a COC at the POE in class 3 groundwater.
(h) Surface water RBEL. The surface water RBEL ( SW RBEL) is the protective concentration of a COC at the POE in surface water. To establish SW RBEL for a COC, the person shall determine the lowest value from paragraphs (1) - (5) of this subsection for each COC, unless the person has sufficient surface water quality information specific to the particular surface water body to support an adjustment to the RBEL in accordance with paragraph (6) of this subsection. The SW RBEL value determined pursuant to paragraphs (1) - (6) of this subsection may require modification in response to the requirements of paragraphs (7) and (8) of this subsection. The SW RBEL value for a given COC shall be protective of relevant downgradient water bodies in consideration of the water body use (e.g., designated drinking water supply or sustainable fishery), the water body type (e.g., estuary or perennial freshwater stream), the standards applicable to the type of water body/use, and the fate and transport characteristics of the COC in question at the particular affected property.
(1) The person shall apply the lower of the acute or chronic criteria for fresh or marine waters as applicable, based on the classification of the surface water, to protect aquatic life as provided in §307.6, Table 1 of this title (relating to Toxic Materials), as amended. The person shall determine the applicability of aquatic life criteria related to the water body aquatic life use and flow conditions in accordance with the procedures contained in §§307.3, 307.4, and 307.6 of this title (relating to Definitions and Abbreviations; General Criteria; and Toxic Materials, respectively), and the agency's Implementation Procedures, as amended, as defined in §350.4 of this title (relating to Definitions and Acronyms), as amended. For fresh waters, the person shall calculate aquatic life criteria for metals with hardness-dependent criteria using the hardness value for the nearest downstream classified segment, as listed in the agency's Implementation Procedures, as amended. Where no value is provided in the Implementation Procedures, a hardness value of 50 mg/l CaCO 3 shall be used. When applicable, the person shall convert total metal concentrations in surface water or groundwater to dissolved concentrations as described in the agency's Implementation Procedures, as amended. The person may use the basin-specific pH values provided in §307.6, Table 2 of this title, as amended, relevant to the particular affected property for purposes of determining the appropriate values for the pH dependent criteria. The person shall use the total suspended solids concentration for the nearest classified segment, as listed in the agency's Implementation Procedures, as amended.
(2) The person shall apply the human health criteria to protect drinking water and fisheries as provided in Table 3 of §307.6 of this title, as amended. When applicable, the person shall convert total metal concentrations in surface water or groundwater to dissolved concentrations as described in the agency's Implementation Procedures, as amended. The person shall determine the applicability of human health criteria according to the water body uses (e.g., public water supply, sustainable fishery, incidental fishery, and contact recreation) in accordance with the procedures contained in §307.3 and §307.6 of this title, as amended, and the Implementation Procedures, as amended. When a water body is not being evaluated as a drinking water source, the person must determine the necessity to evaluate exposure pathways associated with contact recreation such as incidental ingestion of surface water and dermal contact with surface water. The person shall use the total suspended solids concentration for the nearest classified segment, as listed in the agency's Implementation Procedures, as amended.
(3) The person shall apply the effluent limitations specified in Texas Pollutant Discharge Elimination System (TPDES) General Permit Number TXG830000, as amended, for any release of groundwater or storm water that has been impacted by petroleum fuel (as defined in the general permit).
(4) The person shall apply United States Environmental Protection Agency guidelines or alternate provisions in accordance with §307.6(c)(7) of this title, as amended, when criteria for aquatic life protection are not provided for a COC in §307.6 of this title, Table 1, as amended. In addition, the person shall apply federal guidance criteria (i.e., lower of a federal numerical criterion, MCL, or equivalent state drinking water guideline) or alternate provisions in accordance with §307.6(d)(8) of this title, as amended, when human health criteria for a COC are not provided in Table 3 of §307.6 of this title, as amended.
(5) The person shall apply the numerical criteria, as appropriate, for chlorides, sulfates, total dissolved solids, and pH for classified segments as specified in §307.10(1) of this title (relating to Appendices A - G ), as amended.
(6) The person may apply additional provisions where data on surface water quality for a specific surface water body at the affected property is available or can be reasonably obtained.
(7) The additional numeric and narrative criteria listed in subparagraphs (A) and (B) of this paragraph may require development of a surface water RBEL (e.g., where a nutrient is a COC) or modification to the surface water RBEL (e.g., lower a RBEL value to minimize foaming on the water's surface) determined pursuant to paragraphs (1) - (5) of this subsection.
(8) If the executive director determines that the release has the potential to lower the surface water dissolved oxygen, then the executive director may require the person to apply the dissolved oxygen criteria for classified segments specified in §307.10(1) of this title, as amended, or the dissolved oxygen criteria for unclassified waters specified in §307.10(4) of this title, as amended, §307.4(h) of this title, as amended, and §307.7(b)(3)(A) of this title (relating to Site Specific Uses and Criteria), as amended.
(i) Aesthetics. For COCs for which a RBEL cannot be calculated by the procedures of this section, or the RBEL concentration for the COC otherwise adversely impacts environmental quality or public welfare and safety, presents objectionable characteristics (e.g., taste, odor), or makes a natural resource unfit for use, the person shall comply with paragraphs (1) - (3) of this subsection as appropriate. For response actions which are triggered for an area solely for purposes of this subsection (i.e., there is no other human health or ecological hazard remaining), the executive director will evaluate the seriousness, probable longevity of the matter, and suitability of the proposed remedy with the landowner in order to site-specifically Cont'd...