Many industrial and military facilities overlie fractured-rock aquifers in the United States. Fractured-rock aquifers are one of the most complex settings for remediation. Few studies have evaluated or compared contaminant mass removal by pump-and-treat (P&T), monitored natural attenuation (MNA), or enhanced biodegradation (EB) in fractured-rock aquifers, partly because of the perceived hydrogeologic complexity, the lack of understanding of the processes controlling the migration and transformation of contaminants, and the lack of sufficient field data for calculating mass removed. There is a critical need for this evaluation to determine the relative efficiencies of P&T, MNA, and EB remedial strategies in fractured rock. The Naval Air Warfare Center (NAWC) in West Trenton, New Jersey, is well-suited for such an investigation. At this site, there is existing detailed characterization of the fractured sedimentary rock hydrogeologic framework and spatial distribution of chlorinated volatile organic compound (CVOC) contamination, as well as ongoing investigations of subsurface properties and rates that play key roles in mass removal processes. This information has paved the way for a focused assessment and comparison of CVOC mass removal by P&T, MNA, and EB.

The objective of this project is to evaluate and compare CVOC removal and destruction from the well-characterized NAWC site by three remediation technologies—P&T, MNA, and EB—and to better understand the hydrogeologic and biogeochemical mechanisms that control contaminant removal by P&T and destruction by MNA and EB in fractured rock.

(A) Schematic cross section of geology at the NAWC in West Trenton, New Jersey and (B) schematic diagram of the processes affecting the fate of CVOCs in fractured-rock aquifers

In this project, researchers will develop and apply methods for collecting field data necessary to evaluate the fate of CVOCs in fractured-rock aquifers, implement in-situ bioaugmentation to assess the EB strategy, and calculate the rate of mass removal for the three remedial strategies. The existing and ongoing multidisciplinary investigations at NAWC will be leveraged together with results from these investigations to evaluate mass removal. Using a phased approach, researchers first will collect four critical data types under MNA and P&T conditions within an in-situ test facility at NAWC, where trichloroethene (TCE) concentrations are as high as 100,000 μg/L: (1) contaminant mass in the primary porosity; (2) effective porosity and specific surface area of fractures; (3) sources, composition, and bioavailability of organic carbon; and (4) biodegradation rates in open and closed fractures. They then will conduct in-situ bioaugmentation and focus data collection on properties and processes controlling mass removal by EB. Finally, mass removal rates for the three remedial strategies will be calculated by a mass flux approach based on an integrated mass balance and numerical simulations with a reactive transport model constrained by field data.

Evaluating the cost and efficiency of three commonly used remedial technologies in the complex geologic setting of fractured rock will have broad applicability to Department of Defense, Department of Energy, and industrial facilities in similar geologic terrain. Benefits of this investigation include development of cost-effective field methods for collecting data critical to evaluating contaminant mass removal; fundamental insight into the important physical and biogeochemical controls on mass removal rates achieved by P&T, MNA, and EB; guidelines for implementing bioaugmentation and biostimulation remedies in fractured-rock settings; and insight into the advantages and limitations of mass removal calculations by integrated mass balance and numerical simulation. Evaluation of mass removed at NAWC also will directly benefit the selection of cost-effective remedial strategies at this site. (Anticipated Project Completion – 2018)

Imgrigiotta, T. E., A. M. Shapiro, D. J. Goode, and C. R. Tiedeman. 2017. Biogeochemical Analyses of Water Samples Collected in the Mudstone Aquifer Underlying the Naval Air Warfare Center, West Trenton, NJ (2008-2013): U.S. Geological Survey Data Release. https://doi.org/10.5066/F7N877ZC.

Shapiro, A. M. and C. E. Evans. 2017. Data from Mercury Intrusion Porosimetry Conducted on Samples of a Mudstone

Underlying the Naval Air Warfare Center, West Trenton, New Jersey. U.S. Geological Survey Data Release. https://doi.org/10.5066/F7GX48RZ.  

Shapiro, A. M., C. E. Evans, and E. C. Hayes. 2017. Porosity and Pore Size Distribution in a Sedimentary Rock: Implications for the Distribution of Chlorinated Solvents. Journal of Contaminant Hydrology, 203:70-84. https://doi.org/10.1016/j.jconhyd.2017.06.006.

Shapiro, A. M., C. R. Tiedeman, T. E. Imbrigiotta, D. J. Goode, P. A. Hsieh, P. J. Lacombe, M. F. DeFlaun, S. R. Drew, and G. P. Curtis. 2018. Bioremediation in Fractured Rock: 2. Mobilization of Chloroethene Compounds from the Rock Matrix. Groundwater, 56(2):317-336. https://doi.org/10.1111/gwat.12586. 

Shapiro, A. M., D. J. Goode, T. E. Imbrigiotta, M. M. Lorah, and  C. R. Tiedeman. 2019. The Complex Spatial Distribution of Trichloroethene and the Probability of NAPL Occurrence in the Rock Matrix of a Mudstone Aquifer. Journal of Contaminant Hydrology, 223:103478. https://doi.org/10.1016/j.jconhyd.2019.04.001.

Shapiro, A. M. and E. C. Hayes. 2017. Lithologic Characterization of Cores from Boreholes 83BR-89BR Collected from the Mudstone Aquifer Underlying the Naval Air Warfare Center, West Trenton, New Jersey. U.S. Geological Survey Data Release. https://doi.org/10.5066/F70Z71GM.

Shapiro, A. M., M. M. Lorah, T. E. Imbrigiotta, and D. J. Goode. 2019. Concentrations of Chlorinated Ethene Compounds in Rock Core Collected from Boreholes 83BR, 84BR, 85BR, 86BR, 87BR, 88BR, and 89BR in the Mudstone Underlying the Former Naval Air Warfare Center, West Trenton, New Jersey. U.S. Geological Survey Data Release. https://doi.org/10.5066/F7P55MD8. 

Shapiro, A. M. and R. J, Brenneis. 2018. Variability of Organic Carbon Content and the Retention and Release of Trichloroethene in the Rock Matrix of a Mudstone Aquifer. Journal of Contaminant Hydrology, 217:32-42. https://doi.org/10.1016/j.jconhyd.2018.09.001.

Shapiro, A. M. and R. J. Brenneis. 2018. Organic and Total Carbon Analyses of Rock Core Collected from Boreholes 83BR, 84BR, 85BR, 86BR, 87BR, 88BR, and 89BR in the Mudstone Underlying the Former Naval Air Warfare Center, West Trenton, New Jersey. U.S. Geological Survey Data Release. https://doi.org/10.5066/F75719Z7.  

Tiedeman, C. R., A. M. Shapiro, P. A. Hsieh, T. E. Imbrigiotta, D. J. Goode, P. J. Lacombe, M. F. DeFlaun, S. R. Drew, C. D. Johnson, J. H. Williams, and G. P Curtis. 2018. Bioremediation in Fractured Rock: 1. Modeling to Inform Design, Monitoring, and Expectations. Groundwater, 56(2):300-316.  https://doi.org/10.1111/gwat.12585.