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Vickie Reat and Larry Champagne TCEQ Remediation Division

Determining Representative Concentrations for Ecological Receptors and Update on Ecological Risk Assessment Guidance. Vickie Reat and Larry Champagne TCEQ Remediation Division. What This Means. Vickie will discuss

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Vickie Reat and Larry Champagne TCEQ Remediation Division

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  1. Determining Representative Concentrations for Ecological Receptors and Update on Ecological Risk Assessment Guidance Vickie Reat and Larry Champagne TCEQ Remediation Division

  2. What This Means Vickie will discuss • Overview of new TRRP guidance titled, Determining Representative Concentrations of Chemicals of Concern for Ecological Receptors (RG-366/TRRP-15eco); November 2013 Larry will discuss • Updates on Ecological Risk Assessment Guidance (ERAG)

  3. Guidance Development • Collaborative work group effort • Work group of consultants, industry, staff, and natural resource trustees

  4. Relationship to the ERAG • TRRP-15eco intended to compliment the ERAG and fill in gaps • The ERAG is cross-referenced throughout • Both documents should be consulted by those preparing ecological risk assessments (ERAs)

  5. Intended Audience • Guidance says: “regulated community and environmental professionals” • Intended to provide guidance for persons preparing and reviewing a Tier 2 screening-level ERA

  6. Guidance Facts • 131 pages including 5 appendices • Chapters for each exposure medium (soil, sediment, surface water, and groundwater) • Each chapter has a “Data for Assessment” section • Each chapter discusses exposure areas for various exposure pathways, exposure point concentrations (EPCs), hot spot evaluations, and special considerations for threatened or endangered species

  7. Guidance Facts - Continued • Scientific and regulatory citations are throughout the text with a reference list at the end of the document • The groundwater chapter (Chapter 5) and Appendix D are notable additions that address determination of the groundwater EPC for ecological pathways at the groundwater-to-surface water interface

  8. Key Term: Representative Concentration • The concentration calculated to represent ecological exposure conditions. • Assumed to represent an average level of exposure, expressed as a chemical concentration that a receptor may experience over an exposure area or time period consistent with the exposure pathway. • Synonymous with Exposure Point Concentration (EPC). This term is used throughout the guidance. • This value is used to calculate wildlife receptor hazard quotients.

  9. Wildlife, Aquatic Life, and Benthos Exposure Point Concentration (EPC) • Guidance recommends the 95% UCL (upper confidence limit) of the mean as the EPC. Used in the hazard quotient calculations for wildlife, aquatic life, and benthos (after benchmark screening). • Considered a conservative estimate of the true mean of the data set. • No particular software recommended. • Hot spot analysis is also required; hot spots should not be included in the 95% UCL (assuming they are addressed).

  10. Data for Assessment - General • Section for each medium. • Not intended to replace other sampling guidance and data quality objective-type documents. • Intended to provide “do what makes sense” recommendations to obtain a representative data set appropriate for assessing ecological risks. • Guidance highlights typical problem areas.

  11. Hot Spots - Definitions • ERAG: “What constitutes a hot spot depends in part on the concentration, toxicity, and other properties of the chemical of concern (COC), the medium in which it is detected, the extent of the area with elevated COC concentrations, and the biological characteristics such as receptor home range.” • A discrete area of substantially elevated COC concentrations relative to the surrounding area. • Also a function of relative risk to the measurement receptor in question.

  12. Hot Spot Evaluation Goals (Wildlife) • To determine if this area: (1) poses a risk of acute toxicity, or (2) is a preferential exposure (feeding, nesting, or breeding) area relative to the surrounding habitat. • To identify any risks to wildlife receptors that would not be identified and mitigated through the standard risk evaluation, which is based on averaging COC concentrations (i.e., using a 95% UCL as the EPC) across larger areas.

  13. Hot Spot Evaluation Goals (Benthos) • To ensure that a statistical presentation of the data (e.g., 95% UCL) will not mask or dilute areas of elevated sediment concentrations that may otherwise pose a potential risk to the benthic community, or cause risk from the remaining portions of the exposure area to be overestimated. • To facilitate an effective risk management recommendation for potential risks to the benthos, given the uncertainties associated with the assessment of this community.

  14. Hot Spot Evaluation - General • Evaluation is in addition to normal risk evaluation using the 95% UCL as the EPC. • No specific trigger for wildlife; midpoint PCL is trigger for benthic invertebrates. • Guidance suggests various ways to perform a hot spot evaluation for each pathway. • TCEQ will evaluate the adequacy of the analysis and conclusions. • If hot spots are identified, make risk management recommendation.

  15. Soil Exposure Pathways (Chapter 2) 2.1 Data for Assessment 2.2 Exclusion-Criteria Checklist (1-page review) 2.3 Plant and Invertebrate Exposure to Soil (what is protected, why, and upper trophic level connection) 2.4 Exposure of Wildlife Receptors to Soil (exposure areas, exposure point concentrations, evaluation of potential hot spots)

  16. Soil – Data for Assessment Collect samples in ecological habitat – soil that would not meet the Tier 1 exclusion criteria. 2.1.1 Adequacy and Appropriateness of Soil Data 2.1.2 High-Biased and Low-Biased Data Distribution 2.1.3 Soil Depth 2.1.4 Analytical Considerations 2.1.5 Sample Sieving (e.g., at former firing ranges) 2.1.6 Soil vs. Sediment

  17. Soil – Wildlife Exposure Areas Compute the EPC for soils within the exposure area. Generic Approach: assume exposure area is affected property soils within ecological habitat. Ecological habitat = soils that don’t meet the Tier 1 exclusion criteria. Is the affected property contained within land characterized by: pavement, buildings, landscape, equipment storage areas, functioning caps, roadways, manufacturing/process areas, or otherwise disturbed ground?

  18. Not Ecological Habitat!

  19. Soil – Site-Specific Wildlife Exposure Areas When to subdivide? Consider…. • presence of protected species • distinct habitats/unique receptors • patchy ecological habitat or lack of data across patches • risk management reasons to subdivide (e.g., solid waste management units, early removal actions) If subdivided, is the data set sufficiently robust to calculate an EPC?

  20. Sediment Exposure Pathways (Chapter 3) 3.1 Data for Assessment 3.2 Exposure of Benthic Invertebrate Community to Sediment 3.3 Exposure of Wildlife Receptors to Sediment 3.4 Exposure of Fish Receptors to Sediment

  21. Sediment – Data for Assessment 3.1.1 Adequacy and Appropriateness of Sediment Data 3.1.2 Sediment vs. Soil 3.1.3 Sediment Depth 3.1.4 Analytical Considerations 3.1.5 Use of Sediment Pore-Water Data (when, references) 3.1.6 High-Biased and Low- Biased Data Distribution

  22. Sediment (and Surface Water) – Wildlife Exposure Areas • Definition: area within the affected property (AP) throughout which a measurement receptor may move, and where direct or indirect contact with sediment and surface water is likely. • Generic Approach: assume that all AP sediments and surface waters represent a receptor’s exposure area; calculate EPC (i.e., 95% UCL) over entire area. • Site-Specific Approach: Receptor-specific exposure area based on receptor’s ecology and site characteristics. Compute EPC for specific exposure areas.

  23. Sediment and Surface Water – Wildlife Receptor Site-Specific Exposure Areas • Consider presence of a protected species or its habitat. • Consider if the area of sediment use is limited by water depth (e.g., wading birds). • Consider significant differences in physical features (e.g., stream reaches). • Consider risk management and/or programmatic reasons (e.g., SWMUs, early removal).

  24. Sediment (Fish Receptor) Exposure Pathway 3.4.1 Purpose and Rationale 3.4.2 Initial Screen for Evaluating the Sediment-to-Fish Exposure Pathway 3.4.3 Effects Databases for Evaluating the Sediment-to-Fish Exposure Pathway 3.4.4 Assessment Considerations for Fish Communities 3.4.5 Exposure Point Concentration for Fish Communities 3.4.6 Evaluating Sediment Hot Spots for Fish Exposure

  25. Sediment (Fish Receptor) Exposure Pathway

  26. Sediment (Fish Receptor) Exposure Pathway – Hot Spots • Hot Spot Analysis: Perform if a protected fish species is potentially present (for freshwater sites). • There are very few marine protected fish in Texas and marine fish eggs are generally buoyant or pelagic.

  27. Surface Water Exposure Pathways (Chapter 4) 4.1 Data for Assessment 4.2 Aquatic Life Receptors 4.3 Exposure of Wildlife Receptors to Surface Water

  28. Surface Water – Data for Assessment 4.1.1 Routine Monitoring Parameters (in addition to COC analyses) 4.1.2 Sample Depth 4.1.3 Sampling Sequence 4.1.4 Sample Timing, Flow Conditions, and Tidal Influences (especially for lotic waters)

  29. Surface Water – Data for Assessment 4.1.5 Metals in Surface Water (dissolved or total metals, speciation) 4.1.6 Other Analytical Considerations (criteria near detection limits) 4.1.7 Sampling Seeps

  30. Surface Water – Hot Spot Evaluation for Aquatic Life • Evaluation not usually necessary (mobility of aquatic life and transient nature of COCs in surface water) • Necessary if protected freshwater fish, amphibians, or invertebrates (e.g., mollusks) are potentially present. More likely necessary for unique watersheds. • Data uncertainty more problematic (sample density, timing). Conchos pupfish

  31. Surface Water – Hot Spot Evaluation for Wildlife Rarely necessary. Specifically consider: • Impacted playa lake used as a water source (primary or sole source of water) • Springs or seeps (particularly arid portions of state) • Potential exposure for protected amphibian species

  32. Groundwater as a Source Medium for Surface Water and Sediment (Chapter 5) 5.1 Data for assessment 5.2 Appropriateness of a gw-to-surface water dilution factor (mentions TRRP-24 guidance) 5.3 Determining the gw concentration at the gw-to-sw interface 5.4 Groundwater exposure point concentration for the gw-to-sw pathway 5.5 Evaluation of the gw-to-sediment pathway

  33. Determining the Groundwater Concentration at the GW-SW Interface What gw concentration should be used in the ERA? • General practice has been to calc. 95% UCL across wells or use historical max. concentration. • Guidance recommends using highest (current) gw concentration at the interface (across wells) as a conservative approach, or • Determine a discharge-weighted gw concentration across the interface that accounts for variable gw flow and variable COC concentrations across the interface, and spacing of monitoring wells.

  34. Groundwater EPC for the GW-SW Pathway Normally use process detailed in Appendix D (discharge-weighted representative concentration) to derive EPC for aquatic life and wildlife receptors. Exceptions: • Gw seepage to isolated water bodies used by protected species. • Gw discharge at discrete locations (e.g., paleo-channels, utility corridors). • Seepage areas attractive to wildlife & aquatic life. • Use maximum gw concentration in these cases for impacts represented by one or a small number of wells.

  35. Appendices • A – Use of Composite Samples in ERAs • B – Outliers • C – Examples of Sediment Data Groupings (esp. for benthos) • D – Discharge-Weighted Representative Groundwater Concentration at the GW-SW Interface • E – Assessing and Managing Impacts on Protected Species

  36. Appendix D – Discharge-Weighted Representative Groundwater Concentration at the GW-SW Interface • Detailed appendix for determining a representative concentration for groundwater (Cgw) across a groundwater monitoring well network at the gw-sw interface. • Step-by-step presentation of equations (and derivation thereof) for determining a discharge-weighted Cgw. • More complex formulas are presented depending on whether hydraulic conductivity, hydraulic gradient, thickness of saturated zone and effective porosity have constant values across the interface.

  37. Appendix D - Continued This is a diagram from the guidance depicting the groundwater-plume seepage face at the surface water interface. This diagram shows a plume of affected groundwater discharging into a stream channel. The outline of the subsurface groundwater plume non-detect isoconcentration contour is traced onto the ground surface. A linear array of four groundwater monitoring wells occur in and around the affected groundwater plume. The monitoring array is placed close to and parallel with the stream channel to serve as the groundwater-surface water monitoring network for groundwater discharge to the surface water body. Arrows of varying size approximate vectors for groundwater discharge along the groundwater-surface water interface. One large arrow represents the average COC concentration of affected groundwater entering surface water. Another large arrow placed in the stream shows surface water flow direction and discharge rate.

  38. Appendix D - Continued

  39. Appendix D - Continued • Section D.1 presents an example problem for a groundwater plume of TCE with five monitoring wells. • A Cgw calculator spreadsheet is posted on the TCEQ web site with the TRRP-15eco guidance (see next slide). C gw

  40. Excel Cgw Calculator • The calculator solves the general condition described in the worksheet titled "EQ 12" • Enter data only in the available (unprotected) cells • BEGIN by entering monitoring well designations starting with "Well 1," and consistent with the order presented in Figure D.2 and reproduced here - Up to 10 interface monitoring wells may be entered • Enter distances between wells as shown in Figure D.2

  41. Excel Cgw Calculator – Cont. • Enter remaining COC and aquifer parameter data from each respective monitoring well • Enter values in units denoted • Representative groundwater concentration, Cgw, is displayed in blue box at bottom • Delete data in columns with no well designation (table contains example D.1 information - replace with site well information)

  42. Excel Cgw Calculator – Cont.

  43. Update on ERA Guidance I am slightly new and slightly improved! ERAG

  44. Conducting Ecological Risk Assessments at Remediation Sites in Texas, RG-263 Revised January 2014 • Available online at the ERA Home Page: http://www.tceq.state.tx.us/remediation/eco/eco.html, or • The TRRP Guidance and Forms Page: http://www.tceq.state.tx.us/remediation/trrp/guidance.html.

  45. Update on ERA Guidance The primary differences between this draft and earlier versions are: • Most recent surface water screening benchmarks are included • 2007 revisions to the TRRP rule are incorporated • Text has been edited for conciseness • Text has been made accessible ERAG

  46. Update on ERA Guidance Current revision efforts include: • Making the screening benchmark tables and supporting text a separate file from the main text • Incorporating other existing agency documents (e.g., TRRP-15eco) • Building stronger connections between the guidance text and the Ecological PCL Database • Updating the science and associated references where possible

  47. Update on ERA Guidance Future plans include: • Sending out a revised draft to the multi-stakeholder Ecological Workgroup • Meeting with the workgroup to discuss their comments and additions • Incorporating workgroup revisions • Finalizing the document and sending it out for agency review • Posting it to the web

  48. Questions?

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