1. FSA Groundwater Flow and Solute Transport Model Presentation to Scottsdale Citizens Group March 19, 1999

2. Overview of NIBW Site History

3. Overview of Work Comprehensive site characterization Summary of Site conditions in RI/FS Implementation of ROD-required Remedy –Capture and containment not achieved Implementation of Enhanced Remedy –Capture and containment projected (preliminary data and modeling) Preparation of FSA –Additional support for capture and containment projections (performance evaluation and modeling)

4. Components of ROD-Required Remedy MAU & LAU extraction at wells COS31, COS71, COS72, and COS75 Monitoring of UAU mass flux Soil vapor extraction at Areas 7, 8, and 12

5. Voluntary Components of the Enhanced Remedy COS6 tie-in to the CGTF (MAU/LAU) Replacement LAU extraction at well COS75A LAU extraction at well PCX-1 MRTF for treatment of groundwater from PCX-1, and PVWC#15 and #14 UAU extraction at Area 7 MAU extraction at Areas 7 and 12

6. FSA Groundwater Flow and Solute Transport Model

7. Purpose Predictive tool for evaluating a range of remedial actions with respect to: –Capture and containment of the zones of contamination (flow model) –Relative clean-up time (transport model)

8. What is a Groundwater Flow and Solute Transport Model? Mathematical representation of physical system and processes Groundwater flow model - solves for distribution of head Contaminant transport model - solves for concentration of solute as affected by physical and chemical processes

9. Model Development Process Development of conceptual model Model construction Model calibration Projection of future conditions

10. Development of Conceptual Model - Vadose Zone Shallow soil gas sampling programs Installation and sampling of vapor monitor wells Installation and sampling of soil vapor extraction wells Analysis of potential groundwater threat

11. AREA 12 SVE PROGRAM

12. Conceptual Model - Vadose Zone Generally coarse-grained sediments Previous movement of mass from the vadose zone to UAU groundwater at source areas No current impact to groundwater above MCLs

13. Development of Conceptual Model - UAU Installation, testing, and monitoring of about 70 UAU monitor wells Characterization of Southwest Margin Inorganic water quality evaluation

14. UAU WATER LEVEL CONTOURS APRIL 1998

15. UAU TCE CONCENTRATION CONTOURS APRIL 1998

16. SCHEMATIC OF SOUTHWEST MARGIN HYDROGEOLOGY

17. Conceptual Model - UAU Generally coarse-grained Small saturated thickness in south, unsaturated in north and west Flow from east to west or northeast to southwest toward Southwest Margin Downward hydraulic gradients to MAU Downward flow toward underlying units at Southwest Margin Small TCE mass; decreasing over time

18. Development of Conceptual Model - MAU Installation, testing, and monitoring of more than 50 MAU monitor wells Installation and testing of MAU extraction wells at two source areas Aquifer testing at production wells Conduit well investigations Simulprobe sampling program Coring program

19. UPPER MAU WATER LEVEL CONTOURS APRIL 1998

20. LOWER MAU WATER LEVEL CONTOURS APRIL 1998

21. UPPER MAU TCE CONCENTRATION CONTOURS APRIL 1998

22. LOWER MAU TCE CONCENTRATION CONTOURS APRIL 1998

23. BOREHOLE FLOW UNDER NON-PUMPING CONDITIONS

24. CORE SAMPLES FROM MAU MONITOR WELL PG-46MA

25. SIMULPROBE SAMPLER

26. MAU CROSS-SECTION AREA 7

27. MAU CROSS-SECTION AREA 12

28. Conceptual Model - MAU Generally fine-grained with thin coarse- grained interbeds More coarse-grained interbeds in upper MAU Convergent flow toward OU extraction wells and Southwest Margin Downward hydraulic gradients to LAU TCE primarily in upper MAU

29. Development of Conceptual Model - LAU Installation, testing, and monitoring of more that 30 LAU monitor wells Regional water level survey Installation and testing of extraction wells COS75A and PCX-1 Fluid movement and depth-sampling investigations Aquifer testing at production wells

30. LAU WATER LEVEL CONTOURS APRIL 1998

31. REGIONAL LAU WATER LEVEL CONTOURS 1996

32. EXTRACTION WELL COS75A INSTALLATION

33. EXTRACTION WELL PCX-1 INSTALLATION

34. HYDROGEOLOGIC DATA FOR EXTRACTION WELL PCX-1

35. FLUID MOVEMENT LOGGING

36. SPINNER FLOWMETER TOOL

37. DEPTH SAMPLING

38. BOREHOLE FLOW UNDER PUMPING CONDITIONS

39. LAU CROSS-SECTION

40. Conceptual Model - LAU Generally coarse-grained with fine- grained interbeds Increasing lithification and consolidation with depth Decreasing permeability and yield with depth Convergent flow toward PVWC wellfield TCE concentrations generally largest in upper LAU

41. Model Development Process Development of conceptual model Model construction Model calibration Projection of future conditions

42. Model Construction Define model domain Assign model boundary conditions Develop model grid Define model layers Assign pumpage at production wells to model layers Assign hydraulic parameters Assign initial water level and TCE conditions

43. FSA MODEL DOMAIN AND BOUNDARIES (66 sq. mi.) GENERAL HEAD BOUNDARY GENERAL HEAD BOUNDARY NO FLOW BOUNDARY

44. FSA MODEL GRID max = 1,320 ft min = 200 ft

45. MODEL LAYERS 1 2 3 4 5 6 7 8 9 10

46. PUMPING DISTRIBUTION BETWEEN MODEL LAYERS

47. UPPER MAU (LAYER 3) PERCENT COARSE-GRAINED SEDIMENTS

48. UPPER MAU (LAYER 3) TRANSMISSIVITY DISTRIBUTION FROM PUMPING TESTS

49. LAYER 3 TRANSMISSIVITY DISTRIBUTION FROM MODEL

50. Model Development Process Development of conceptual model Model construction Model calibration Projection of future conditions

51. Model Calibration Process of adjusting parameters within bounds of data to obtain best match to observed conditions Calibration period – 1990 through 1996 – Selected based on data availability

52. COMPARISON OF OBSERVED (APRIL 1997) AND SIMULATED WATER LEVELS UAU SIMULATED OBSERVED

53. COMPARISON OF OBSERVED (APRIL 1997) AND SIMULATED WATER LEVELS MAU SIMULATED OBSERVED

54. COMPARISON OF OBSERVED (APRIL 1997) AND SIMULATED WATER LEVELS LAU SIMULATED OBSERVED

55. COMPARISON OF OBSERVED (APRIL 1997) AND SIMULATED TCE CONCENTRATIONS UAU SIMULATED OBSERVED

56. COMPARISON OF OBSERVED (APRIL 1997) AND SIMULATED TCE CONCENTRATIONS MAU SIMULATED OBSERVED

57. COMPARISON OF OBSERVED (APRIL 1997) AND SIMULATED TCE CONCENTRATIONS LAU SIMULATED OBSERVED

58. Model Development Process Development of conceptual model Model construction Model calibration Projection of future conditions

59. Projection of Future Conditions Prepare pumping input files –Based on projections by water providers –Generally reflect 1996 conditions Compare ROD Required and Enhanced Remedial Alternatives Simulate range of potential additional Remedial Actions Simulate combinations of Remedial Actions comprising potential Remedial Alternatives

61. EnhancedROD

62. Layer 3 TCE Concentrations ROD-Required and Enhanced Remedies, Year 2028

63. Layer 6 TCE Concentrations ROD-Required and Enhanced Remedies, Year 2028

68. Anticipated Schedule for FSA Process