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A Natural Attenuation Toolbox for Metals and Radionuclides

SAND99-0464. Unlimited Release Printed March 1999. Site Screening and Technical Guidance for Monitored Natural Attenuation at DOE Sites 1. PATRICK V. BRADY, 2 BRIAN P. SPALDING, 3 KENNETH M. KRUPKA, 4. ROBERT D. WATERS, 1 PENGCHU ZHANG, 5 DAVID J. BORNS, 6 WARREN D. BRADY. 1. Geochemistry Dept. (MS-0750), Sandia National Laboratories, Albuquerque, New Mexico 87185- 2 3. 0750. Oak Ridge National Laboratories, Box 2008 Oak Ridge TN 37831-6036 . Applied Geology and Geochemistry, Pacific Northwest National Laboratory, Richland, Washington, Box 4. 999 / MS K6-81 Richland, WA 99352 . Director - National TRU Program, Sandia National 5. Laboratories, Carlsbad, New Mexico (MS-1395). Geophysics Department (MS-0750), Sandia 6. National Laboratories, Albuquerque, New Mexico 87185-0750. IT Corporation, Baton Rouge, Louisiana. Abstract Site Screening and Technical Guidance for Monitored Natural Attenuation at DOE Sites briefly outlines the biological and geochemical origins of Natural Attenuation , the tendency for Natural processes in soils to mitigate contaminant transport and availability, and the means for relying on monitored Natural Attenuation (MNA) for remediation of contaminated soils and groundwaters.

3 SAND99-0464 Unlimited Release Printed March 1999 Site Screening and Technical Guidance for Monitored Natural Attenuation at DOE Sites 1PATRICK V. BRADY, 2BRIAN P. SPALDING, 3KENNETH M. KRUPKA, 4ROBERT D. WATERS, 1PENGCHU ZHANG, 5DAVID J. BORNS, 6WARREN D. BRADY 1Geochemistry Dept. (MS-0750), Sandia National Laboratories, Albuquerque, New Mexico …

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Transcription of A Natural Attenuation Toolbox for Metals and Radionuclides

1 SAND99-0464. Unlimited Release Printed March 1999. Site Screening and Technical Guidance for Monitored Natural Attenuation at DOE Sites 1. PATRICK V. BRADY, 2 BRIAN P. SPALDING, 3 KENNETH M. KRUPKA, 4. ROBERT D. WATERS, 1 PENGCHU ZHANG, 5 DAVID J. BORNS, 6 WARREN D. BRADY. 1. Geochemistry Dept. (MS-0750), Sandia National Laboratories, Albuquerque, New Mexico 87185- 2 3. 0750. Oak Ridge National Laboratories, Box 2008 Oak Ridge TN 37831-6036 . Applied Geology and Geochemistry, Pacific Northwest National Laboratory, Richland, Washington, Box 4. 999 / MS K6-81 Richland, WA 99352 . Director - National TRU Program, Sandia National 5. Laboratories, Carlsbad, New Mexico (MS-1395). Geophysics Department (MS-0750), Sandia 6. National Laboratories, Albuquerque, New Mexico 87185-0750. IT Corporation, Baton Rouge, Louisiana. Abstract Site Screening and Technical Guidance for Monitored Natural Attenuation at DOE Sites briefly outlines the biological and geochemical origins of Natural Attenuation , the tendency for Natural processes in soils to mitigate contaminant transport and availability, and the means for relying on monitored Natural Attenuation (MNA) for remediation of contaminated soils and groundwaters.

2 This report contains a step-by-step guide for (1) screening contaminated soils and groundwaters on the basis of their potential for remediation by Natural Attenuation and (2) implementing MNA consistent with EPA OSWER Directive The screening and implementation procedures are set up as a web-based tool ( ) to assist Department of Energy (DOE) site environmental managers and their staff and contractors to adhere to EPA guidelines for implementing MNA. This document is intended to support the Decision Maker's Framework Guide and Monitoring Guide both to be issued from DOE EM-40. Further technical advances may cause some of the approach outlined in this document to change over time. 3. Acknowledgements We greatly appreciate financial support from DOE-EM-47 - Steven C. Golian, as well as support from Jim Bachmaier (DOE-EH) and Beth Moore (DOE-Las Vegas). Grace Bujewski (SNL) provided a lot of the early push for this project. PVB. gratefully acknowledges additional financial support from the SNL-Laboratory Directed Research and Development office, technical editing from Judy Campbell, HTML assistance from Michael Townsend, and javascript direction from Hai Le.

3 WDB acknowledges the support of International Technologies Corporation. We greatly appreciate helpful technical input from David Rice (LLNL), Eric R. Lindgren (SNL), Gaynor Dawson and Jason Erdman (Project Performance Corporation). Charles Bryan (SNL) kindly provided us with Table Lastly, Diane Marozas (SNL) provided a lot of the early inspiration for MNAtoolbox, and Gaynor Dawson contributed a number of the later ideas. 4. Contents 9. THE EPA MNA 10. OBJECTIVES OF OSWER 11. DATA 12. SITE SCREENING .. 14. SITE SCREENING .. 14. SITE CHARACTERIZATION .. 15. 17. FUTURE USE CONSIDERATIONS .. 19. TECHNICAL APPROACHES .. 20. MNATOOLBOX .. 21. MODELS FOR Natural Attenuation OF ORGANIC CONTAMINANTS .. 23. MODELS FOR Natural Attenuation OF 27. MNA SCORECARD .. 29. Hydrologic Dilution Factor (HDF).. 31. Sorption Factor (SF) .. 32. Organics ..33. Inorganics ..33. Irreversible Uptake (Rirv).. 35. Inorganics ..36. Organics ..37. Biodegradation/Chemical Transformation (BF) .. 41. Calculation of the 42.

4 Geochemical Summaries of How Specific Inorganics Are Dealt With in MNAtoolbox ..44. MNAIMPLEMENT .. 48. COLLECTION OF MNA-SPECIFIC DATA .. 48. REFINEMENT OF CONCEPTUAL 50. FORWARD-MODELING OF 51. LONG-TERM MONITORING FOR 53. REFERENCES CITED .. 55. APPENDIX A. THE OSWER MNA DIRECTIVE .. 67. APPENDIX B. THE AFCEE PROTOCOL FOR MNA OF FUEL HYDROCARBONS .. 93. APPENDIX C. THE AFCEE PROTOCOL FOR MNA OF CHLORINATED ORGANICS .. 101. APPENDIX D. THE RTDF GUIDANCE HANDBOOK FOR MNA OF CHLORINATED 107. APPENDIX E. INORGANIC REACTIVITY .. 115. APPENDIX F. MEASUREMENT OF IRREVERSIBLE UPTAKE OF INORGANIC CONTAMINANTS .. 137. 5. Figures Figure Conceptual model of site processes and characteristics required to describe contaminant 15. Figure Outline of MNA approach.. 22. Figure Degradation paths for chlorinated 25. Figure Good and bad scenarios for chlorinated organic breakdown.. 26. Figure Schematic of Natural processes and variables contributing to the calculation of the NAF. 30. Figure Distribution coefficient (Kds) used in the calculation of the NAF for metal 34.

5 Figure Irreversible and reversible sorption of organic contaminants normalized to organic carbon levels (OC = and f =1).. 40. Figure Ratio of irreversible to total sorption of organic contaminants normalized to organic carbon levels as a function of solution contaminant levels (OC = and f =1).. 40. Figure Relation between NAF and Score.. 43. Figure Two-site Langmuir model for calculating irreversible uptake.. 53. Tables Table Progressive Monitoring Steps for Remediation By MNA .. 18. Table Natural Attenuation Pathways for 28. Table Octanol-Water Coefficients for Primary Organic Contaminants of Concern to DOE .. 33. Table Fraction of Contaminant Metal Taken Up Irreversibly (default values) .. 37. Table Sorption and Solubility Parameters of Selected Organic Contaminants .. 39. Table Biodegradation and Radionuclide Decay 41. Table SDWA Limits for Radionuclides (from 40 CFR Part ) .. 46. Table MCL, DCF, and Limiting Molar Concentrations for Radionuclides .. 47. 6. Nomenclature [>-i] sorbed concentration of contaminant i AFCEE U.

6 S. Air Force Center for Environmental Excellence BF biodegradation/chemical transformation Factor BTEX benzene toluene ethylbenzene xylene CERCLA Comprehensive Environmental Response Compensation and Liability Act C contaminant concentration Cmax maximum contaminant concentration measured in the soil Co initial concentration of contaminant Cs contaminant sorption capacity Csx contaminant sorption capacity for weak (reversible) sites Csy contaminant sorption capacity for strong (irreversible) sites Ct contaminant concentration as a function of time CT carbon tetrachloride d mixing zone depth (m). da aquifer depth (m). DCA dichloroethane DCE dichloroethylene DCF dose conversion factor DL dose limit from SDWA. DNAPL dense nonaqueous phase liquid DOE Department of Energy DTPA diethylenediaminepentaacetic acid EDTA ethylenedinitrilotetraacetic acid EPA Environmental Protection Agency f fraction of the irreversible compartment (organics) that is filled at the time of exposure HDF hydrologic dilution factor i hydraulic gradient (m/m).

7 Aq i the dissolved concentration of contaminant i tot i total amount of contaminant in rock or soil -1. k degradation rate constant (yr ). kl Langmuir constant proportional to the binding strength of a contaminant Kd sorption coefficient (ml/g). Kh hydrologic conductivity (m/yr). irv K oc organic carbon-normalized partition coefficient Koc soil adsorption coefficient normalized to organic carbon content (L/kg). Kom soil adsorption coefficient normalized to OC organic matter (L/kg). Kow octanol water partition coefficient (L/kg). Kp predicted equilibrium partition constant Kx binding constant for weak sites Ky binding constant for strong sites l recharge rate (m/yr). L length of source parallel to flow (m). LC limiting concentration Mi molar concentration (mol/L). MCL maximum contaminant level MNA monitored Natural Attenuation Na Avogadro's number NAF Natural Attenuation factor ne effective aquifer porosity NTA nitrilotriacetic acid OC organic carbon om soil organic matter content (kg/kg).

8 OSWER Office of Solid Waste and Emergency Response 7. PCA tetrachloroethane PCE perchloroethylene q total adsorption (organics)( g/g). qirv Irreversible adsorption (organics)( g/g). irv q max maximum irreversible adsorption level (organics) ( g/g). qrev reversible adsorption (organics)( g/g). Rirv irreversible uptake factor RCRA Resource Conservation and Recovery Act ROD Record of Decision RTDF Remediation Technologies Development Forum SDWA Safe Drinking Water Act SEP Sequential Extraction Procedure SF sorption factor t1/2 radioactive half-life (yr). TCA tricholoroethane TCE trichloroethylene TCLP toxicity characteristic leaching procedure VC vinyl chloride VOL volume of water or leachate in equilibrium Volrock volume of soil estimated to be encountered by a plume (L). v subsurface velocity of dissolved contaminant Vs horizontal seepage velocity WC water consumption rate (L/yr). WT weight of soil or rock in equilibrium x distance the contaminant travels in groundwater (m).

9 X reversible weak sites Xirv irreversible uptake fraction Xt a known or measurable amount of contaminant Y irreversible strong sites v vertical dispersivity (m). bulk density (kg/L). b bulk rock density 8. Introduction According to the Environmental Protection Agency's (EPA's) Office of Solid Waste and Emergency Response (OSWER) Directive , Natural Attenuation is defined as the naturally occurring processes in soils and groundwaters that act without human intervention to reduce the mass, toxicity, mobility, volume, or concentration of contaminants in those media. These in situ processes include biodegradation, dispersion, dilution, sorption, precipitation, volatilization, and/or chemical and biochemical stabilization of contaminants ( Environmental Protection Agency, 1997). This document outlines a site-screening procedure for assessing the importance of Natural Attenuation and provides technical guidance for relying on Natural Attenuation at contaminated soils and groundwaters at Department of Energy (DOE) sites.

10 The object of this document is to provide site managers, the target audience, the general technical background needed to consider remediation by Natural Attenuation . The sections that follow define Natural Attenuation , broadly outline how conceptual models are used to address and implement monitored Natural Attenuation (MNA) and then link the achievement of cleanup goals with Natural Attenuation processes. Specific questions that must be answered for successful reliance on MNA at sites include: 1. Is Natural Attenuation occurring? 2. If so, are reductions in potential contaminant impacts decreasing rapidly enough to achieve regulatory compliance in an acceptable time frame? 3. Is Natural Attenuation sufficiently widespread and reliable to assure remedial goals are achieved? 4. How much long-term monitoring is required? 5. What is the cost of MNA in comparison to other remediation techniques? Development of site-specific conceptual models describing contaminant transport in the subsurface is meant to answer each of these questions.


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