Assessing the Long-Term Performance and Impacts of ISCO and ISBR Remediation Technologies

Dr. Mark Brusseau | University of Arizona

ER-201585

Objective

The overall objective of this project is to improve the Department of Defense’s (DoD) long-term environmental risk management capabilities and reduce the remediation costs for sites contaminated with chlorinated solvents, 1,4-dioxane, perchlorate, and other hazardous compounds. Several innovative technologies exist to remediate these sites, and the performance of these technologies has been demonstrated by numerous site installation restoration projects and SERDP- or ESTCP-funded projects. However, performance assessments are typically conducted over short-term time scales. As a result, the long-term performance of these technologies is unknown, which serves as a barrier to their cost-effective implementation. There is a critical need to conduct accurate, quantitative performance assessments over longer time scales. This is especially important for the many complex sites that contain large groundwater contaminant plumes comprising persistent contamination, which are recognized to present the most difficult challenges to site closure. This project will assess and compare the long-term performance of three high-profile remediation technologies: in situ chemical oxidation (ISCO), enhanced reductive dechlorination (ERD), and enhanced aerobic cometabolism (EAC). The project also will investigate the impacts of technology application on groundwater quality, and delineate site conditions that foster or limit the long-term performance of these technologies.

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Technology Description

The project will be conducted at the Air Force Plant 44 (AFP44) site, which is part of the Tucson International Airport Area (TIAA) federal Superfund site located in Tucson, Arizona. The remediation projects were conducted at the three designated dense nonaqueous phase liquid (DNAPL) source zones of the AFP44 site. The projects focused on the saturated-zone portion of the source zones and the interface between the vadose zone and saturated zone. This interface region, which consists of primarily lower-permeability (clay) media, has been identified as the primary location for remaining contaminant. Slow release of contaminant from this domain is considered to be the primary cause of the observed rate-limited mass removal and delayed attainment of cleanup objectives. In addition, hydraulic containment has been implemented at a fourth source zone (3H), with no other technologies used. Three metrics will be used for the performance assessment: (1) change in aggregate contaminant of concern (COC) concentration for groundwater samples collected from multiple monitoring wells located within the treatment zone; (2) change in contaminant mass discharge (CMD) based on CMD tests conducted in the treatment zone before and after the ISCO; and (3) change in plume-scale composite CMD based on continuous monitoring of groundwater extracted with the pump-and-treat system.

201585_project_graphic

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Benefits

This project will apply standard and innovative metrics to conduct long-term performance assessments of three high-profile, widely used remediation technologies: ISCO, ERD, and EAC. Successful completion of the project will generate critical information that will benefit remedial project managers and other end users at sites impacted by persistent groundwater contamination. The dissemination of this information will improve the cost-effective implementation of these technologies, which has the potential to substantially reduce the DoD cost burden for management of groundwater-contaminated sites. (Anticipated Project Completion - 2018)

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Publications

Brusseau, M.L. and Z. Guo. 2018. The Integrated Contaminant Elution and Tracer Test Toolkit, ICET3, for Improved Characterization of Mass Transfer, Attenuation, and Mass Removal. Journal of Contaminant Hydrology, 208:17-26.

Guo, Z. and M.L. Brusseau. 2017. The impact of Well-Field Configuration and Permeability Heterogeneity on Contaminant Mass Removal and Plume Persistence. Journal of Hazardous Materials, 333:109–115.

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Points of Contact

Principal Investigator

Dr. Mark Brusseau

University of Arizona

Phone: 602-621-3244

Fax: 602-621-1647

Program Manager

Environmental Restoration

SERDP and ESTCP

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