# Contamination, risk, and heterogeneity: on the effectiveness of aquifer remediation

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## Abstract

The effectiveness of aquifer remediation is typically expressed in terms of a reduction in contaminant concentrations relative to a regulated maximum contaminant level (MCL), and is usually confirmed by sparse monitoring data and/or simple model calculations. Here, the effectiveness of remediation is re-examined from a more thorough risk-based perspective that goes beyond the traditional MCL concept. A methodology is employed to evaluate the health risk to individuals exposed to contaminated household water that is produced from groundwater. This approach explicitly accounts for differences in risk arising from variability in individual physiology and water use, the uncertainty in estimating chemical carcinogenesis for different individuals, and the uncertainties and variability in contaminant concentrations within groundwater as affected by transport through heterogeneous geologic media. A hypothetical contamination scenario is developed as a case study in a saturated, alluvial aquifer underlying an actual Superfund site. A baseline (unremediated) human exposure and health risk scenario, as induced by contaminated groundwater pumped from this site, is predicted and compared with a similar estimate based upon pump-and-treat exposure intervention. The predicted reduction in risk in the remediation scenario is not an equitable one—that is, it is not uniform to all individuals within a population and varies according to the level of uncertainty in prediction. The importance of understanding the detailed hydrogeologic connections that are established in the heterogeneous geologic regime between the contaminated source, municipal receptors, and remediation wells, and its relationship to this uncertainty is demonstrated. Using two alternative pumping rates, we develop cost-benefit curves based upon reduced exposure and risk to different individuals within the population, under the presence of uncertainty.

## Keywords

Hydraulic Conductivity Debris Flow United States Environmental Protection Agency Contaminant Concentration Maximum Contaminant Level## Notes

### Acknowledgments

This work was supported in part by the Lawrence Livermore National Laboratory postdoctoral program. This work was conducted under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under contract W-7405-Eng-48.

## References

- Agterberg FP(1974) Geomathematics. Elsevier, Amsterdam, 596 pGoogle Scholar
- Anderson MP (1989) Hydrogeologic facies models to delineate large-scale spatial trends in glacial and glaciofluvial sediments. J Sediment Petrol 40:298–323Google Scholar
- Ashby SF, Falgout RD (1996) A parallel multigrid predconditioned conjugate gradient algorithm for groundwater flow simulations. Nucl Sci Eng 124(1):145–159Google Scholar
- Anderson MP, Woessner WW (1992) Applied groundwater modeling. Academic, San Diego, 391 pGoogle Scholar
- Bishop D, Rice D, Rogers L, Webster-Scholten C (1990) Comparison of field-based distribution coefficients (Kd’s) and retardation factors (R’s) to laboratory and other determinations of Kd’s, Rep. UCRL-AR-105002. Lawrence Livermore National Laboratory, LivermoreGoogle Scholar
- Bogen KT, Spear RC (1987) Integrating uncertainty and interindividual variability in environmental risk assessment. Risk Anal 7(4):427–436CrossRefGoogle Scholar
- Burmaster DE, Wilson AM (1996) An introduction to second-order random variables in human health risk assessments. Hum Ecol Risk Assess 2(4):892–919Google Scholar
- Carle SF (1996) A transition probability-based apprach to geostatistical characterization of hydrostratographic architecture, Ph.D. Dissertation, University of California, Davis, 238 pGoogle Scholar
- Carle SF (1997) Implementation schemes for avoiding artifact discontinuities in simulated annealing. Math Geol 29(2):231–244CrossRefGoogle Scholar
- Carle SF, Fogg GE (1996) Transition probability-based indicator geostatistics. Math Geol 28(4):453–476CrossRefGoogle Scholar
- Carle SF, Fogg GE (1997) Modeling spatial variability with one and multidimensional continuous-lag Markov chains. Math Geol 29(7):891–918CrossRefGoogle Scholar
- Carle SF, Labolle EM, Weissmann GS, Van Brocklin D, Fogg GE (1998) Conditional simulation of hydrofacies architecture: a transition probability/Markov approach. In: Fraser GS, Davis JM (eds) Hydrogeologic models of sedimentary aquifers, concepts in hydrogeology and environmental geology No. 1. Society for Sedimentary Geology, Tulsa (SEPM), pp 147–170Google Scholar
- Carpenter DW, Sweeney PW, Kasameyer PW, Burkhard NR, Knauss KG, Shlemon RJ (1984) Geology of the Lawrence Livermore National Laboratory site and adjacent areas. Lawrence Livermore National Laboratory, Livermore (UCRL-53316)Google Scholar
- Chen Y-C, Ma H-W (2006) Model comparison for risk assesment: a case study of contaminanted groundwater. Chemosphere 63:751–761CrossRefGoogle Scholar
- Desbarats A (1990) Macrodispersion in sand-shale sequences. Water Resour Res 26(1):153–163CrossRefGoogle Scholar
- Fleckenstein JH, Niswonger RG, Fogg GE (2006) River-aquifer interactions, geologic heterogeneity, and low flow management. Ground Water 44(6):837–852CrossRefGoogle Scholar
- Fogg GE, Carle SF, Green C (2000) A connected-network paradigm for the alluvial aquifer system, in press. In: Zhang D (ed) Theory, modeling and field investigation in hydrogeology: a special volume in honor of Shlomo P. Neuman’s 60th birthday, Geological Society of America Special PublicationGoogle Scholar
- Fogg GE, Noyes CD, Carle SF (1998) Geologically based model of heterogeneous hydraulic conductivity in an alluvial setting. Hydrogeol J 6:131–143CrossRefGoogle Scholar
- Jones JE, Woodward CS (2001) Integrated surface-groundwater flow modeling: a free-surface overland flow boundary condition in a parallel groundwater flow model. Adv Water Resour 24:763–774CrossRefGoogle Scholar
- Kollet SJ, Maxwell RM (2006) Integrated surface-groundwater flow modeling: a free-surface overland flow boundary condition in a parallel groundwater flow model. Adv Water Resour 29:945–958CrossRefGoogle Scholar
- LaBolle EM, Fogg GE, Tompson AFB (1996) Random-walk simulation of transport in heterogeneous porous media: local mass-conservation problem and implementation methods. Water Resour Res 32(3):583–593CrossRefGoogle Scholar
- Ma HW (2002) Stochastic multimedia risk assessment for a site with contaminated groundwater. Stoch Environ Res Risk Assess 16:464–478CrossRefGoogle Scholar
- Massmann J, Freeze RA (1987a) Groundwater contamination from waste management sites: the interaction between risk-based engineering design and regulatory policy, 1, methodology. Water Resour Res 23(2):351–367CrossRefGoogle Scholar
- Massmann J, Freeze RA (1987b) Groundwater contamination from waste management sites: the interaction between risk-based engineering design and regulatory policy, 2, results. Water Resour Res 23(2):368–380CrossRefGoogle Scholar
- Massmann J, Freeze RA, Smith L, Sperling T, James B (1991) Hydrogeological decision analysis, 2, applications to groundwater contamination. Ground Water 29(4):536–548CrossRefGoogle Scholar
- Maxwell RM (1998) The effects of uncertainty and variability in groundwater-driven health risk assessment. Ph.D. Dissertation, University of California, Berkeley, 157 pGoogle Scholar
- Maxwell RM, Kastenberg WE (1999a) A model for assessing and managing the risks of environmental lead emissions. Stoch Environ Res Risk Assess 13(4):231–250CrossRefGoogle Scholar
- Maxwell RM, Kastenberg WE (1999b) Stochastic environmental risk analysis: an integrated methodology for predicting cancer risk from contaminated groundwater. Stoch Environ Res Risk Assess 13(1–2):27–47Google Scholar
- Maxwell RM, Tompson AFB (2006) SLIM-FAST: a user’s manual, Lawrence Livermore National Laboratory, Livermore, California, UCRL-SM-225092, 49 pGoogle Scholar
- Maxwell RM, Pelmulder SD, Tompson AFB, Kastenberg WE (1998) On the development of a new methodology for groundwater-driven health risk assessment. Water Resour Res 34(4):833–847CrossRefGoogle Scholar
- Maxwell RM, Kastenberg WE, Rubin Y (1999) A methodology to integrate site characterization information into groundwater-driven health risk assessment. Water Resour Res 35(9):2841–2856CrossRefGoogle Scholar
- Maxwell RM, Welty C, Tompson AFB (2003) Streamline-based simulation of virus transport resulting from long term artificial recharge in a heterogeneous aquifer. Adv Water Resour 22(3):203–221Google Scholar
- Morgan MG (2000) Risk management should be about efficiency and equity. Environ Sci Technol 34:32A–34ACrossRefGoogle Scholar
- NRC (1994) Science and judgement in risk assessment. National Academy Press, Washington, 651 pGoogle Scholar
- NRC (1999) Environmental cleanup at navy facilities: risk-based methods. National Academy Press, Washington, 143 pGoogle Scholar
- NRC (2003) Environmental cleanup at navy facilities: adaptive site management. National Academy Press, Washington, 376 pGoogle Scholar
- Noyes CD (1991) Hydrostratigraphic analysis of the pilot remediation test area, Lawrence Livermore National Laboratory, Livermore, California, M.S. Thesis, University of California, Davis, 165 pGoogle Scholar
- Pelmulder SD, Yeh WW-G, Kastenberg WE (1996) Regional scale framework for modeling water resources and health risk problems. Water Resour Res 32(6):1851–1861CrossRefGoogle Scholar
- Qualheim BJ (1988) Well log report for the LLNL ground water project 1984–1987. Lawrence Livermore National Laboratory, Livermore, UCID-21342Google Scholar
- Reichard EG, Evans JS (1989) Assessing the value of hydrogeologic information for risk-based remedial action decisions. Water Resour Res 25(7):1451–1460CrossRefGoogle Scholar
- Schafer-Perini AL, Wilson JL (1991) Efficient and accurate front tracking for two-dimensional groundwater flow models. Water Resour Res 27(7):1471–1485CrossRefGoogle Scholar
- Smalley JB, Minsker BS, Goldberg DE (2000) Risk-based in situ bioremediation design using a noisy genetic algorithm. Water Resour Res 36(10):3043–3052CrossRefGoogle Scholar
- Springer JE (1984) Structural development of the Livermore Basin, California: LLNL UCRL-91431, 58 pGoogle Scholar
- Tompson AFB (1993) Numerical simulation of chemical migration in physically and chemically heterogeneous porous media. Water Resour Res 29(11):3709–3726CrossRefGoogle Scholar
- Tompson AFB, Dougherty DE (1992) Particle-grid methods for reacting flows in porous media with application to Fisher’s equation. Appl Math Model 16:374–383CrossRefGoogle Scholar
- Tompson AFB, Jackson KJ (1996) Reactive transport in heterogeneous systems: an overview. Rev Mineral 34:269–310Google Scholar
- Tompson AFB, Vomoris EG, Gelhar LW (1987) Numerical simulation of solute transport in randomly heterogeneous porous media: motivation, model development, and application. Lawrence Livermore National Laboratory, Livermore, UCID-21281Google Scholar
- Tompson AFB, Carle SF, Rosenberg ND, Maxwell RM (1999) Analysis of groundwater migration from artificial recharge in a large urban aquifer: a simulation perspective. Water Resour Res 35(10):2981–2998CrossRefGoogle Scholar
- Tompson AFB, Falgout RD, Smith SG, Bosl WJ, Ashby SF (1998) Analysis of subsurface contaminant migration and remediation using high performance computing. Adv Water Resour 22(3):203–221CrossRefGoogle Scholar
- USEPA (1989) Risk assessment guidance for superfund volume I: human health manual (Part A). Office of emergency and remedial response, Washington, EPA/540/1-89/002Google Scholar
- USEPA (2001) Risk assessment guidance for superfund volume III—Part A, process for conducting probabilistic risk assessment. Office of emergency and remedial response, Washington, EPA/540-R-02-002Google Scholar
- Walker RG (ed) (1981) Facies models. Geoscience Canada reprint series 1, geoscience Canada, Toronto, 211 pGoogle Scholar
- Walker RG, James NP (1992) Facies models: response to sea level change: Geological Association of Canada, St. John’s, Newfoundland, 409 pGoogle Scholar
- Walther J (1894) Einleitung in die Geologie als Historische Wissenschaft: Bd. 3, Lithogenesis der Gegenwart. Fischer Verlag, Jena, pp 535–1055Google Scholar
- Weissmann GS, Carle SF, Fogg GE (1999) Three dimensional hydrofacies modeling based on soil surveys and transition probability geostatistics. Water Resour Res 35(6):1761–1770CrossRefGoogle Scholar