The objective of this project was to field-validate the horizontal reactive media treatment well (HRX Well®), a new in situ remediation approach that uses directionally drilled horizontal wells filled with granular reactive treatment media. Groundwater is treated in situ as it flows through the HRX Well. The HRX Well concept is well-suited for sites where long-term mass discharge control is a primary performance objective and is particularly appropriate for recalcitrant and difficult-to-treat constituents, including chlorinated solvents, per- and polyfluoroalkyl substances (PFAS), 1,4-dioxane, and metals.


Project Summary

Technology Description

The HRX Well concept leverages natural “flow-focusing” behavior created by the well-to-aquifer permeability contrast to capture and passively treat proportionally large volumes of groundwater in situ. Treated groundwater exiting the HRX Well results in cleanup of the downgradient aquifer via elution. For this project, the HRX Well was operated in a fully passive configuration; however, for some higher-permeability aquifers, the HRX Well capture zone size and performance may be enhanced through pumping (i.e., active configuration).

HRX Well Summary

Demonstration Results

The demonstration was conducted at Site 003 at Vandenberg Air Force Base in Central California. The numerical model-predicted in-well flow and capture width of the HRX Well was consistent with estimates derived from Darcy’s Law calculations, Point Velocity Probe testing, and tracer testing. The actual average HRX Well capture zone width was likely between 45 and 69 feet. Trichloroethene (TCE) was treated in the HRX Well abiotically with zero valent iron and total TCE mass discharge reduction was >99.99 % relative to the upgradient well. Significant biologically mediated treatment also occurred, facilitated by the residual guar-based biopolymer drilling fluid. After 436 days, decreases from 50 to 74% in TCE were observed at four down-gradient monitoring wells, and the timing of the first arrival of treated water was consistent with model predictions. The demonstration confirmed HRX Wells can be installed under active infrastructure, require limited ongoing operation and maintenance, and have low lifecycle energy and water requirements. For this site, estimated lifecycle HRX Well costs were lower than costs for permeable reactive barrier and pump and treat alternatives.

Implementation Issues

The HRX Well uses a combination of standard commercial off the shelf materials and custom-built prototypes. The mud rotary directional drilling method used is applicable to both unconsolidated and bedrock aquifer settings. Site lithology and hydrogeology can pose performance risks for the HRX Well technology. In high hydraulic conductivity settings, the HRX Well can be operated in a pumping “active configuration”; however, high flow rates through the well and shorter residence times in the treatment media could become a limiting factor. The effects of incomplete recovery of the biopolymer drilling fluid should be considered in treatability testing. (Project Completion - 2020)


Divine, C.E., J. Wang, and M. Crimi. 2018. Reply to Comments. Groundwater Monitoring & Remediation, 38(3):15-16. doi.org/10.1111/gwmr.12288.

Divine, C.E., J. Wright, J. Wang, J. McDonough, M. Kladias, M. Crimi, B.N. Nzeribe, J.F. Devlin, M. Lubrecht, D. Ombalski, W. Hodge, H. Voscott, and K. Gerber. 2018. The Horizontal Reactive Media Treatment Well (HRX Well®) for Passive In Situ Remediation: Design, Implementation, and Sustainability. Remediation Journal, 28(4):5-16. doi.org/10.1002/rem.21571.

Divine, C.E., J. Wright, M. Crimi, J.F. Devlin, M. Lubrecht, J. Wang, J. McDonough, M. Kladias, J. Hinkle, A. Cormican, T. Osorno, B.N. Nzeribe, F. Laramay, D. Ombalski, K. Gerber, and H. Anderson. 2020. Field Demonstration of the Horizontal Reactive Media Treatment Well (HRX Well®) for Passive In-Situ Remediation. Groundwater Monitoring & Remediation, 40(3):42-554. doi.org/10.1111/gwmr.12407.

Divine, C.E., T. Roth, M. Crimi, A.C. DiMarco, M. Spurlin, J. Gillow, and G. Leone. 2018. The Horizontal Reactive Media Treatment Well (HRX Well®) for Passive In-Situ Remediation. Groundwater Monitoring & Remediation, 38(1):56-65. doi.org/10.1111/gwmr.12252.

Horst, J., C. Divine, M. Schnobrich, R. Oesterreich, and J. Munholland. 2019. Groundwater Remediation in Low‐Permeability Settings: The Evolving Spectrum of Proven and Potential. Groundwater Monitoring & Remediation, 39(1):11-19. doi.org/10.1111/gwmr.12316.

Theses and Dissertations

DiMarco, A. 2016. Laboratory Testing and Validation of Directional Horizontal Wells for In Situ Groundwater Remediation (Master's Thesis). Clarkson University.

Li, W. 2019.  Meshfree Methods Based on Radial Basis Functions for Solving Partial Differential Equations: From Strong Form to Weakened Weak Form (Ph.D. Dissertation). Clarkson University.

Nzeribe Nwedo, B. 2019. The Horizontal Reactive Media Treatment Well (HRX Well) for Passive In Situ Remediation (Ph.D. Dissertation). Clarkson University.


Ditto, J., C.E. Divine, M.D. Lubrecht, D.W. Ombalski, and J.B. Wright. 2019. Groundwater Treatment Systems and Methods. U.S. Patent Application No. 62703336.