SECTION 350.77. Ecological Risk Assessment and Development of Ecological Protective Concentration Levels

(a) General. The person shall evaluate the affected property by conducting an ecological risk assessment in a manner appropriate and consistent with subsections (b), (c), or (d) of this section. The process is discussed in the agency's ecological risk assessment guidance. The purpose of the ecological risk assessment will be to characterize the ecological setting of the affected property, identify complete or reasonably anticipated to be completed exposure pathways and representative ecological receptors, scientifically eliminate COCs that pose no unacceptable risk, and develop PCLs for selected ecological receptors where warranted. The POEs for the selected ecological receptors shall be established on a property-specific basis. However, if the person can show that no unacceptable ecological risk exists due to incomplete or insignificant exposure pathways as specified in subsection (b) of this section, or if all COCs can be eliminated as specified in subsection (c)(1), (6), (7), or (8) of this section, or if, after incorporation of site-specific information, it can be shown that there is either no ecological risk or that it is not apparent as specified in subsection (d) of this section, then the ecological risk assessment process will terminate at that point. Also, if after the ecological risk assessment process specified in subsection (b) of this section, or if at anytime during the ecological risk assessment process specified in subsections (c) or (d) of this section, the person can demonstrate to the satisfaction of the executive director that the implementation of a response action will eliminate the ecological exposure pathway or render it insignificant, or that human health PCLs will be protective of ecological receptors, then no further ecological risk assessment evaluation will be required. In addition, if after the ecological risk assessment process specified in subsection (b) of this section, the person can demonstrate to the satisfaction of the executive director that an expedited stream evaluation can determine that the completed surface water and sediment pathways are insignificant, then no further ecological risk assessment evaluation will be required. If no further ecological risk assessment evaluation is required, then the person shall provide, as appropriate, a reasoned justification and/or an expedited stream evaluation for terminating the ecological risk assessment and place this information in the affected property assessment report as described in §350.91 of this title (relating to Affected Property Assessment Report). Furthermore, after ecological PCLs have been established, the person shall have the option, where determined appropriate, of conducting an ecological services analysis as a means of managing ecological risk at the affected property, in accordance with subsection (f) of this section and §350.33(a)(3)(B) of this title (relating to Remedy Standard B). Subsections (b), (c), and (d) of this section describe a three-tiered approach to conducting an ecological risk assessment, and although there is a logical progression from one tier to the next, the person may begin the ecological evaluation of the affected property at any tier.

(b) Tier 1: exclusion criteria checklist. The person shall conduct a Tier 1 assessment at all affected properties to which this rule is applicable as presented in §350.2 of this title (relating to Applicability), unless the person elects to begin the ecological evaluation at Tier 2 or Tier 3. The person shall use the Tier 1 Exclusion Criteria Checklist provided in the following figure. The person will have fulfilled the ecological risk assessment requirements if the affected property meets the exclusion criteria. However, the person shall re-enter the ecological risk assessment process if changing circumstances result in the affected property not meeting the Tier 1 exclusion criteria. The person is required to continue the ecological risk assessment process as described in subsection (c) or (d) of this section if the affected property fails the exclusion criteria, unless the reasoned justification and/or expedited stream evaluation processes described in subsection (a) of this section are used to demonstrate that no unacceptable ecological risk exists.

Attached Graphic

(c) Tier 2: screening-level ecological risk assessment. The person shall conduct a screening-level ecological risk assessment to scientifically eliminate COCs that do not pose an ecological risk and to develop PCLs for those COCs that do pose an unacceptable risk to selected ecological receptors. Effect levels and exposure factors from the literature are used as early input, but Tier 2 PCLs are not developed without consideration of realistic assumptions and available site-specific information. The screening-level ecological risk assessment should contain the three following widely-acknowledged phases of an ecological risk assessment: problem formulation, which establishes the goals, breadth, and focus of the assessment; analysis, which consists of the technical evaluation of data on both the exposure of the ecological receptor to a chemical stressor and the potential adverse effects; and risk characterization, where the likelihood of adverse effects occurring as a result of exposure to a chemical stressor is evaluated. In order to develop a screening-level ecological risk assessment which appropriately evaluates ecological risk, the person shall meet the minimum requirements listed in paragraphs (1) - (10) of this subsection. Additional information on these requirements, as well as case examples, are provided in the agency's ecological assessment guidance. The person shall:

(1) use affected property concentrations of non-bioaccumulative COCs to compare to established ecological benchmarks and/or use approved methodologies to develop benchmarks to determine potential effects and to eliminate COCs that do not pose unacceptable ecological risk (if all COCs are eliminated at this point, the ecological risk assessment process ends and the items listed in paragraphs (2) - (9) of this subsection are not required);

(2) identify communities (e.g., soil invertebrates, benthic invertebrates) and major feeding guilds (e.g., omnivorous mammals, piscivorous birds) and their representative species which are supported by habitats on the affected property for each complete or reasonably anticipated to be completed exposure pathway;

(3) develop a conceptual model which graphically depicts the movement of COCs through media to communities and the feeding guilds;

(4) discuss COC fate and transport and toxicological profiles;

(5) prepare a list of input data which includes values from the literature (e.g., exposure factors, intake equations that account for total exposure, no observed adverse effect level (NOAEL) and lowest observed adverse effect level (LOAEL) values, references), any available site-specific data, and reasonably conservative exposure assumptions, and then calculate the total exposure to selected ecological receptors from each COC not eliminated according to paragraph (1) of this subsection and present these calculations in tables or spreadsheets;

(6) utilize an ecological hazard quotient methodology to compare exposures to the NOAELs in order to eliminate COCs that pose no unacceptable risk (i.e., NOAEL hazard quotient less than or equal to 1); however, when multiple members of a class of COCs are present which exert additive effects, it is also appropriate to utilize an ecological hazard index methodology (if all COCs are eliminated at this point, the ecological risk assessment process ends and the items listed in paragraphs (7) - (9) of this subsection are not required);

(7) justify the use of less conservative assumptions (e.g., a larger home range) to adjust the exposure and repeat the hazard quotient exercise in paragraph (6) of this subsection, once again eliminating COCs that pose no unacceptable risk based on comparisons to the NOAELs and adding another set of comparisons, this time to the LOAELs, for those COCs indicating a potential risk (i.e., NOAEL hazard quotient >1); however, when multiple members of a class of COCs are present which exert additive effects, it is also appropriate to utilize an ecological hazard index methodology (if all COCs are eliminated at this point, the ecological risk assessment process ends and the items listed in paragraphs (8) and (9) of this subsection are not required);

(8) develop an "uncertainty analysis" which discusses the major areas of uncertainty associated with the screening-level ecological risk assessment, including a justification for not developing PCLs for particular COCs/pathways, if appropriate (e.g., NOAEL hazard quotient > 1 > LOAEL hazard quotient, an evaluation of the likelihood of ecological risk, a discussion of the half-life of the COCs, etc.); however, when multiple members of a class of COCs are present which exert additive effects, it is also appropriate to utilize an ecological hazard index methodology (if all COCs are eliminated at this point, the ecological risk assessment process ends and the item listed in paragraph (9) of this subsection is not required);

(9) calculate medium-specific PCLs bounded by the NOAEL and the LOAEL used in paragraph (7) of this subsection for those COCs that are not eliminated as a result of the hazard quotient exercises or the uncertainty analysis; and

(10) make a recommendation for managing ecological risk at the affected property based on the final ecological PCLs, unless proceeding under Tier 3 (may be included as part of the affected property assessment report, self-implementation notice, or the response action plan).

(d) Tier 3: site-specific ecological risk assessment. When any of the Tier 2 PCLs, as described in subsection (c) of this section, are considered by the person to be inappropriate or not reflective of existing conditions at the affected property, or when otherwise elected, the person may conduct a site-specific ecological risk assessment. If the person elects to begin the ecological evaluation of the affected property by proceeding directly to a site-specific ecological risk assessment, applicable components of a Tier 2 screening-level ecological risk assessment shall be incorporated, including subsections (c)(2) - (4), (8), and (10) of this section and other requirements of subsection (c) of this section as determined appropriate by the executive director. The purpose of the optional site-specific ecological risk assessment shall be to incorporate additional information obtained through the performance of site-specific studies designed to provide a more empirical evaluation of ecological risk at the affected property. The result of the site-specific ecological risk assessment will be the development of site-specific Tier 3 PCLs, a determination that there is no ecological risk, or a conclusion that ecological risk is not apparent based on site-specific information. Site-specific studies which may be conducted include but are not limited to:

(1) development of site-specific bioaccumulation factors through the collection and analysis of tissue samples from appropriate ecological receptors.

(2) performance of toxicological testing of the impacted media via exposure to an appropriate test species.

(3) comparison of site data (e.g., macroinvertebrate diversity surveys) to like data from a reference area.

(4) other studies designed to obtain a preponderance or "weight-of-evidence" to draw conclusions about ecological risk.

(e) Cross-media transfers of COCs. In situations where cross-media transfer of a COC from a source medium to a POE within an exposure medium must occur for the receptor to be exposed, then the person shall use the cross-media natural attenuation factor equations as shown in the figure in §350.75(b)(1) of this title (relating to Tiered Human Health Protective Concentration Level Evaluation) to calculate the PCL. In lieu of using the human health RBEL referenced in the figures, the person shall use the ecological PCL established under subsections (c) or (d) of this section.

(f) Ecological risk management options. After the ecological risk has been quantified and PCLs have been established as specified in subsections (c) or (d) of this section and it has been determined that the ecological PCL is the critical PCL, or is the only PCL, the person may either:

(1) take action to remove and/or decontaminate the impacted media and COCs as described in §350.32 of this title (relating to Remedy Standard A); or

(2) remove, decontaminate, and/or control the impacted media and COCs or, when after consultation with the Natural Resource Trustees, it is determined appropriate by the executive director, conduct an ecological services analysis in accordance with §350.33 of this title (relating to Remedy Standard B). The ecological services analysis considers the ecological risks and benefits of the potential response actions available under Remedy Standard B at the affected property and, as appropriate, factors in compensatory ecological restoration in lieu of or in addition to remediation as a means of managing residual ecological risk.

Source Note: The provisions of this §350.77 adopted to be effective September 23, 1999, 24 TexReg 7436; amended to be effective March 19, 2007, 32 TexReg 1526; amended to be effective March 19, 2009, 34 TexReg 1866