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Perchlorate Monitoring in Llagas Groundwater Subbasin, South Santa Clara County

Explore the investigation history, challenges, and innovations in the Olin/Standard Fusee Case Study in California. Learn about the current cleanup efforts, aquifer testing, and groundwater flow analysis. Discover the complexities of characterizing perchlorate contamination and the methods used to address the issue.

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Perchlorate Monitoring in Llagas Groundwater Subbasin, South Santa Clara County

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  1. Perchlorate Monitoring in the Llagas Groundwater SubbasinSouth Santa Clara County, CaliforniaOlin/Standard Fusee Case Study Presented byMichael Taraszki, PG, CHG Engineering and Consulting, Inc.

  2. Outline • Investigation History • Current Cleanup and Abatement Order (CAO) • Characterization Elements and Challenges • Status of Investigation

  3. Investigation History • Perchlorate Tested/Observed Beneath Morgan Hill Site in 2000 • Site Investigation Expanded to Include Offsite Private Wells • Continued Presence of Perchlorate Required Rapid Expansion of Monitoring Program • Over 200 Wells >PHG (6 mg/L) by 2004 • Only 33 Wells >PHG Currently

  4. Perchlorate Non-Detect GW Flow

  5. Perchlorate >4 mg/L <6 mg/L GW Flow

  6. Perchlorate >6 mg/L GW Flow

  7. All Perchlorate Results GW Flow

  8. Investigation Overview • Current Cleanup and Abatement Order Requirements • Characterization Elements • Lateral/Vertical Extent of Perchlorate • Background Concentration Evaluation • Establish GW Flow Directions, Chemical Signatures, and Aquifer Hydraulic Parameters • Characterization Challenges • Large Scale Project • Significant Technical Issues • Aggressive Schedule • Politically Charged Arena • Investigation Status

  9. Hydrogeology Geology Chemistry Evaluate Existing Data CHARACTERIZATION Acquire New Data Identify Limitations

  10. Detailed Logging of Soil Core

  11. Soil Core Benefits: • Near In-Situ Conditions • Near 100% Recovery • Plastic Wrapping Allows for Labeling • Boxed for Long-Term Storage

  12. Depth-Discrete Slug Testing

  13. Aquifer Hydraulic Testing • In-Situ Drill-String Slug Testing • Conducted During Drilling Activities • 208 Tests Performed to Date • Pneumatic Slug Testing • Conducted In Completed 1-Inch PVC Wells • ‘Passive’ Pumping Response Analysis • Continuously Recorded Water Levels

  14. Slug Test Results Shallow Intermediate Deep

  15. Installing Multi-LevelMonitoring Wells

  16. Mixture of Techniques Initial Borehole &PVC Couplet Second Borehole &CMT Well Depth (ft) 0 Result: Up To Nine Depth-Discrete Intervals at Each Location 100 Borehole 200 Casing 300 Screen 400 450

  17. Monitoring Well Design • Base Design Upon Geologic Log of Continuous Core • Target Zones with Highest Permeability • CMT Well Design Begins with Evaluation of First 300-Feet of Primary Borehole • PVC Couplet Designed • CMT Design Confirmed with Evaluation of Secondary Borehole • Designs Coordinated with RWQCB and SCVWD

  18. CMT Installation: Step 1Layout Work Area

  19. CMT Installation: Step 2 Prepare 300-Foot CMT Coil

  20. CMT Installation: Step 3Uncoil CMT Material

  21. CMT Installation: Step 4Install Monitoring Ports

  22. CMT Installation: Step 5Install Port Screens

  23. CMT Installation: Step 6Backfill Void Space

  24. CMT Installation: Step 7Install Bottom Plugs

  25. CMT Wellhead SevenMonitoring Ports Sand Drainage ProtectivePVC Sleeve

  26. PVC Couplet Wellhead (in progress)

  27. Completed Well Diagrams Initial Borehole &PVC Couplet Second Borehole &CMT Well Depth (ft) 0 Result: Up To Nine Depth-Discrete Intervals at Each Location 100 Borehole 200 Casing 300 Screen 400 450

  28. Depth-Discrete Groundwater Elevation and Analytical Data

  29. GW Elevation Evaluation • Monitoring Well Elevation Data Will Be Used to Identify: • Vertical Distinction of Aquifer Units • Local Pumping Influences • Depth-Discrete Horizontal Gradients • Utility of Supply Wells

  30. Cross-Section and Groundwater Elevations Northern Half

  31. Cross-Section and Groundwater Elevations Southern Half

  32. Offsite Perchlorate Shallow Aquifer

  33. Offsite Perchlorate Intermediate Aquifer

  34. Offsite Perchlorate Deep Aquifer

  35. Summary • Data Evaluation • Continuous Soil Core • Groundwater Flow Directions • Aquifer Hydraulic Parameters • Perchlorate Distribution/Chemical Signatures • Significant Challenges Being Addressed with Innovative Approaches • Sonic Drilling/Continuous Soil Cores • Multi-Level Monitoring Well Technology • Depth-Discrete Aquifer Testing • Aggressive Investigation Schedule

  36. Contact Information: Michael Taraszki 600 Grand Avenue, Suite 300 Oakland, California 94610 (510) 628-3222 mdtaraszki@mactec.com Petaluma Office: 5341 Old Redwood Hwy, Ste 300Petaluma, CA 94954 Phone: (707) 793-3800 Fax: (707) 793-3900 San Francisco Office: 28 Second Street, Suite 700 San Francisco, CA 94105 Phone: (415) 543-8422 Fax: (415) 777-9706 Sacramento Office: 4704 Roseville Road, Suite 108, North Highlands, CA 95660 Phone: (916) 332-5552 Fax: (916) 332-5559 www.mactec.com

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