Demonstration and Validation of the Horizontal Reactive Media Treatment (HRX) Well for Managing Contaminant Plumes in Complex Geological Environments

Dr. Craig Divine | ARCADIS US, Inc.

ER-201631

Objective

The objective of this project is to field-validate the horizontal reactive media treatment (HRX) well, a new in situ remediation approach offering distinct advantages over traditional approaches for managing dissolved contaminants from source zones in complex geological settings. The approach uses directionally drilled horizontal wells filled with granular reactive media, such as zero valent iron (ZVI), installed in the direction of groundwater flow. Contaminant mass discharge from source zones can be dramatically reduced, which can be cost-effectively sustained over many years. By greatly reducing or eliminating source zone discharge, downgradient plumes can be effectively treated, possibly even achieving low water quality standards in a relatively short period of time. For many of the Department of Defense’s (DoD) sites, it is increasingly recognized that contaminant mass flux and discharge may represent the most appropriate measure of plume strength and potential migration risk; therefore, remedial objectives and technologies focusing primarily on long-term mass discharge reduction will be increasingly favored. The HRX well concept is particularly well-suited for sites where long-term mass discharge control is a primary performance objective.

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Technology Description

The HRX well concept leverages natural “flow-focusing” behavior created by the strong well-to-aquifer permeability contrast to capture and passively treat proportionally large volumes of groundwater in situ. This flow-focusing captures a wide zone of impacted groundwater, which passively flows into the well through the screen at the upgradient portion of the well. Because the well is filled with a reactive media, impacted groundwater is treated in situ as it flows through the well. The treated groundwater then exits the well through the screen along the downgradient sections. The HRX well approach can provide rapid and dramatic reduction in contaminant mass discharge, and it requires no above-ground treatment or footprint and limited ongoing maintenance. Although the HRX well technology has not been field demonstrated to date, the concept has been patented and developed and tested through extensive numerical modeling and physical modeling (i.e., tank testing). This project will: (1) apply the HRX technology to control mass discharge at an appropriate DoD field site; (2) measure the actual hydraulic capture, ZVI treatment efficiency, and mass discharge reduction and compare to model-predicted performance; (3) assess overall technical and sustainability performance of the HRX well; and (4) develop a user-friendly design tool and guidance regarding technology applicability and limitations, anticipated performance, design and installation considerations, and costing.

ER-201631_project_grapihc

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Benefits

The HRX well technology addresses many of the challenges inherent to remediation, including (1) costs and time requirements associated with hydraulic containment (e.g., conventional pump and treat); (2) effective delivery of injected reagent-based strategies; and (3) limitations associated with up-front costs and long-term hydraulics in flow-through permeable reactive barrier (PRB) treatment schemes. It has the potential to significantly improve the management of solvent source zones by providing a reliable method for controlling contaminant migration and mass discharge that requires little long-term maintenance, can be applied in complex geological settings, reduces impact on surface operations, and/or translates to significantly reduced lifecycle costs over currently available alternatives. An approach utilizing HRX wells for a typical trichloroethene (TCE) site may result in savings of approximately half the lifecycle costs. (Anticipated Project Completion - 2019)

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Points of Contact

Principal Investigator

Dr. Craig Divine

ARCADIS-US, Inc.

Phone: 720-308-5367

Program Manager

Environmental Restoration

SERDP and ESTCP

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