Coal Tar DNAPL Mass Removal - Monterey Conference, Neale Misquitta, Key Environmental, Inc.

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Presentation from paper presented at the Monterey Batelle Conference Regarding the authors site specific experiences for the removal of DNAPL at coal tar and creosote wood treating sites. Approximately 40,000 gallons almost 15 tons, of prouct is removed annually using a variety of reovery techniques.

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  • - Productive profitable enterprise - Very environmentally conscious and responsible - Has had several (three) owners over the last 32 years - Environmental activities have been ongoing since 1987
  • Coal Tar DNAPL Mass Removal - Monterey Conference, Neale Misquitta, Key Environmental, Inc.

    1. 1. NAPL MASS REMOVAL AT WOOD TREATING SITES N. J. Misquitta, D.R. Foster, M.D. Brourman
    2. 2. PRESENTATION OUTLINE <ul><li>Introduction </li></ul><ul><li>Remedial Approaches </li></ul><ul><li>NAPL Removal </li></ul><ul><li>NAPL Parameters </li></ul><ul><li>Summary </li></ul>1 2 3 4 5 Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    3. 3. Active Wood Treating and Other Coal Tar Related Projects Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    4. 4. 2007 DNAPL Sites Remedial Approaches Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    5. 5. Technology Screening and Remedial Alternatives <ul><li>Containment Systems </li></ul><ul><ul><li>Best approach for elimination of discharges to surface water </li></ul></ul><ul><ul><li>Slurry walls and sheet pile walls most commonly used </li></ul></ul><ul><ul><li>Groundwater control component often required </li></ul></ul>Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    6. 6. Technology Screening and Remedial Alternatives <ul><li>Containment Systems </li></ul><ul><ul><li>Slurry wall advantages </li></ul></ul><ul><ul><ul><li>No joints – Minimal leak potential </li></ul></ul></ul><ul><ul><ul><li>Aesthetics – Everything is out-of-sight </li></ul></ul></ul><ul><ul><ul><li>Cost Certainty – Not dependent upon price of steel </li></ul></ul></ul>Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    7. 7. Technology Screening and Remedial Alternatives <ul><li>Containment Systems </li></ul><ul><ul><li>Sheet pile wall advantages </li></ul></ul><ul><ul><ul><li>Can be installed at the water’s edge </li></ul></ul></ul><ul><ul><ul><li>Minimal spoils management </li></ul></ul></ul><ul><ul><ul><li>May provide structural support for fill placement </li></ul></ul></ul><ul><ul><li>Potential disadvantage </li></ul></ul><ul><ul><ul><li>Sealing the joints can be a challenge </li></ul></ul></ul>Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    8. 8. Technology Screening and Remedial Alternatives <ul><li>In-situ Stabilization/Solidification </li></ul><ul><ul><li>Recognized as effective technology for creosote, coal tar/DNAPLs </li></ul></ul><ul><ul><li>Permeability reduction results in greatly reduced mass flux of dissolved constituents </li></ul></ul><ul><ul><li>Applicable to shallow sources (generally <15 ft-bgs) </li></ul></ul><ul><ul><li>Portland cement most common reagent; kiln dust, fly ash or lime sometimes used </li></ul></ul><ul><ul><li>Regulatory advocate for ISS Technology – Ed Bates EPA-ORD </li></ul></ul><ul><ul><li>Option for deeper sources – In-Situ BioGeoChemical Stabilization (Adventus Americas) </li></ul></ul>Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    9. 9. Technology Screening and Remedial Alternatives <ul><li>Monitored Natural Attenuation </li></ul><ul><ul><li>From a technical standpoint – MNA should be a “Slam Dunk” for dissolved plumes derived from creosote/coal tar </li></ul></ul><ul><ul><li>Regulators often require some source mitigation in conjunction with MNA </li></ul></ul>Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    10. 10. DNAPL Removal <ul><li>Recovery Wells </li></ul><ul><ul><li>Approach evolved from a O&M cost reduction initiative </li></ul></ul><ul><ul><li>Large diameter sumps for storage reduces O&M </li></ul></ul><ul><ul><li>Wells designed as oil-water separators </li></ul></ul><ul><ul><li>Data show non-detectable oil and grease concentrations in groundwater </li></ul></ul><ul><ul><li>Groundwater produced from active DNAPL recovery operations can be re-circulated or discharged directly to POTW </li></ul></ul>Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    11. 11. DNAPL Recovery: Operations, Maintenance and Monitoring Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    12. 13. Summary: Current KEY DNAPL Remedies <ul><li>Total DNAPL recovery ~40,000 gallons/year cumulatively </li></ul><ul><li>“ Active” DNAPL recovery yields are an order of magnitude greater than “Passive” </li></ul><ul><li>Two sites moved (downgraded) from “Active” to “Passive” recovery </li></ul><ul><li>Groundwater monitoring is conducted at all sites – some reductions in scope negotiated with agencies </li></ul><ul><ul><li>Reduced analysis </li></ul></ul><ul><ul><li>Reduced number of monitoring wells required </li></ul></ul><ul><li>Physical containment remedies at ~6 sites, “Active” DNAPL recovery continues </li></ul><ul><li>Move towards recirculation systems continues </li></ul><ul><ul><li>DNAPL is separated in the well </li></ul></ul><ul><ul><li>Generally cost-effective </li></ul></ul>Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    13. 14. Typical DNAPL Depletion Curve <ul><li>DNAPL Recovery Rate Decreases Over Time </li></ul><ul><li>But, System Changes, Improvements, Optimizations &quot;Re-Start&quot; the Clock </li></ul>MD Site
    14. 15. Relative DNAPL Mobility <ul><li>Resistance to flow is due to capillary forces and viscosity </li></ul><ul><li>Capillary forces impede initial movement and decrease relative permeability </li></ul><ul><li>Viscosity reduces velocity when DNAPL is moving </li></ul><ul><li>Combined effect varies with grain size and pore throat opening </li></ul><ul><li>Increased density increases the vertical movement potential </li></ul>Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    15. 16. DNAPL Parameters <ul><li>Density Ranges from 1.065 to 1.128 g/cc, Mean 1.095 </li></ul><ul><li>Interfacial Tension Ranges from 19.5 to 27.75 dynes / cm 2 , Mean 21.48 </li></ul><ul><li>Viscosity Ranges from 11.84 to 57.09 cP, Mean 21.88 </li></ul>Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    16. 17. Relative DNAPL Mobility Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    17. 18. Relative DNAPL Mobility <ul><li>Variations in pore throat radius and aquifer permeability vary significantly in determining the potential mobility and velocity of DNAPL </li></ul><ul><li>Potential DNAPL velocities are order(s) of magnitude less than groundwater even with high DNAPL saturations </li></ul><ul><li>High combined viscosity and interfacial tension reduces recoverability significantly </li></ul>Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    18. 19. Capillary Resistance to Initial DNAPL Flow Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    19. 20. Fluid Velocity Versus Permeability Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    20. 21. DNAPL Recovery Versus Mobility Factor Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary
    21. 22. Summary <ul><li>DNAPL Removal is Often a Required Component of Site Remediation </li></ul><ul><li>The Ability to Recovery DNAPL Varies Greatly </li></ul><ul><li>The Most Significant Factors are Initial Mass and Geologic Conditions </li></ul><ul><li>DNAPL Recovery May be Modestly Helpful at Some Sites, but Generally is Required by Regulatory and/or Other Goals </li></ul><ul><li>DNAPL Recovery Rates Decrease over Time, However, Improvements / Expansions to Recovery Systems Often Mask the </li></ul>Introduction Remedial Approaches DNAPL Removal DNAPL Parameters Summary

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