Risk Assessment Tools

1. Risk Assessment Tools

2. ComprehensiveModeling and Risk Characterization Software TIER 1 AND TIER 2 RBCA EVALUATIONS forCHEMICAL RELEASE SITES Groundwater Services, Inc.Houston, Texas

3. Objectives of RBCA Process Establish cost-effective risk management system to: n Protect public health and environment nExpedite site remediation / closure process

4. Risk-Based Corrective Action Procedures TRADITIONAL APPROACH RISK-BASED APPROACH Site Investigation Site Investigation Risk Assessment KEY POINT: New step added to define “How Clean is Clean” at each site. Site-Specific Standards Universal Standards Corrective Measure Study Corrective Measure Study Implementation Implementation

5. Risk-Based Calculations x x = Exposure Concentration Exposure Factors Toxicity Health Risk Source Media Concentrations BaselineRisks Forward Mode Calculation Source Media Cleanup Levels Target RiskLimits Backward Mode Calculation

6. AnalyticalF&T Models Standard Exposure Factors User-Input Target Risks Chem/ToxDatabase x x = RBCA Tool Kit Key Software Features Includes system of 10 analytical models for comprehensive evaluation of air, soil, and groundwater exposure pathways.

7. RBCA Tool Kit Matching the Process Model Utilities ReleaseAssessment Conceptual Exposure Model n Exposure Pathways: Define pathways & receptors n Tier 1 & 2 Limits: RBSL and SSTL values for all pathways. n Remedy Selection: Analyses multiple receptors and time. n Action Levels: Limits for any monitoring point. Risk-BasedTarget Limits Remedial Action Compliance Monitoring KEY POINT: Calculation tool for risk-based decision making.

8. RBCA Tool Kit User-Friendly Interface Main Screen

9. RBCA Tool Kit Exposure Pathway Input Multiple Receptors

10. RBCA Tool Kit Exposure Pathway Flowchart

11. RBCA Tool Kit Use Internal or 3rd Party Models Transport Modeling Options

12. RBCA Tool Kit Chemical / Toxicological Database nPetroleum Hydrocarbons nChlorinated Solvents nPesticides nMetals User Customization

13. RBCA Tool Kit Target Limit Calculations Safe soil and groundwater source concentrations ? Report-Quality Output

14. RBCA Tool Kit Transient Modeling Worksheet How soon will impact occur ? User Interactive

15. ? RBCA Tool Kit What’s It Do for Me? What It Does What You Do n Exposure Model n Risk-Based Limits Risk Management Decisions n Remedy Selection Criteria n Compliance Action Levels KEY POINT: Streamline number-crunching to put emphasis on good data, good response measures.

16. RISC

17. Up to 90 chemicals in database, incl. TPH fractions from Air Force Working Group Fate and transport models for soil-to-groundwater, groundwater migration, indoor and outdoor air, and indoor showering Performs forward and backward risk Allows for pathway and compound additivity Monte Carlo features for exposure Presence of mixtures explicitly checked & modeled Version 3.0 Features of RISC

18. Human Health Risk Vegetables grown in contaminated soil Water irrigation pathway New indoor air models with vapor degradation Ecological Risk Surface water and sediment quality databases Mixing of groundwater plumes into surface water body and sediments New Version 4.0 Features

19. Contaminant Water Soil Grain Risk from free productSource Zone Characteristics Residual (Trapped) Water Contaminant Soil Grain Free Phase (Mobile)

20. Vapor models from sources in the vadose zone Johnson and Ettinger (no degradation) Dominant layer model Oxygen-Limited model The vadose zone vapor models may use either a soil concentration or a soil gas concentration for the source term. Vapor model from groundwater May be linked with a groundwater model Indoor Air Models in RISC

21. Dominant Layer Model Ref: Paul Johnson Dominant Layer Model, API Pub. 4674 Layer 1 D3 Layer 2 (biodegradation) D2 D1 Layer 3 Csource Source Concentration

22. Source Pathway Additivity • One source can contribute to multiple pathways: • Vapor inhalation • Drinking water ingestion • Soil ingestion • Vapors during showering Vapors Drinking water Leaching

23. If a chemical is both a carcinogen and a hazard, the clean-up level is calculated using both targets and the lower value becomes the clean-up level. If the “individual” option is chosen, the risk is not added across chemicals, however, all pathways originating from the same source are ALWAYSadded together. If the “cumulative” option is chosen, the risk is apportioned between all of the chemicals (either all hazards or all carcinogens) and the source concentrations are changed relative to the original concentration ratios AAdditivity: rulesusedby RISC RISC

24. Groundwater: Dissolved Phase Model Unsaturated Zone Residual Contamination Saturated Zone Planar Source

25. Specify soil concentration and source volume. Water table may fluctuate, saturating residual. Model calculates effective solubility and accounts for source depletion. Application: When there are measurements of the total soil concentrations at the water table. When water table fluctuations may increase loading during different times of the year. For small sources at the water table. New spills at the water table. Saturated Soil Model

26. For a constant source, increasing degradation decreases time to reach steady-state and decreases plume extent. Effects of Degradation Plume Extent l=0 l=0.001 /day l=0.01 /day

27. Can account for hydrocarbons that are part of a mixture. Considers volatilization losses. Contains a lens option to account for heterogeneity in the soil (variable moisture content)=important for volatilization processes. Conserves mass. Considers degradation. UnsaturatedZone Model

28. Unsaturated zone: Model Schematic The lens is just used to calculate an effective diffusion coefficient between the source and the ground surface. Optional Lens

29. Dissolved-phase transport (advection) Vapor-phase diffusive losses Dispersion in the dissolved phase Degradation Retardation Checks source term for effective solubility Not considered: movement of free-phase product Processes Considered

30. Considered when groundwater is used to water lawns and gardens but household water is supplied by municipality. Potential pathways Incidental ingestion (while swimming or playing) Dermal contact Inhalation of groundwater spray Ingestion of home grown vegetables from irrigation water IrrigationPathways

31. Utilizes surface water and sediment quality criterion as screening device to protect all aquatic (and benthic) life Fate and transport codes combined with surface water mixing and partitioning models to generate concentrations Database in RISC is limited to ‘gold standards’ Surface water: (ANZECC 1992, US EPA AWQCs, UK EQSs) Sediments: NOAA ER-Ms and PELs, etc Aquatic Ecological Modules

32. Source Surface Water Mixing dilution, partitioning Plume Advection, dispersion, biodegradation, sorption

33. Identify receptor to be protected Input transfer factor data bioaccumulation data for water to fish biotransfer factor for soil to plants Input food chain data dietary composition, feeding range, food ingestion rate, etc Estimate receptor dose from simple algorithms Compare receptor dose to toxicity reference values Ecological Approach

34. Risc - Humaan