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U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Horizontal Remediation Wells

Site Application Examples

The following references illustrate site-specific applications of HDD to environmental remediation.


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Groundwater Extraction, Extraction of Free-Phase Product, and Dual-Phase Extraction | Groundwater Recirculation | Air Sparging and Soil Vapor Extraction (SVE) | Bioremediation | Chemical Injection | In Situ Thermal Treatment | Permeable Reactive Barriers and Biobarriers | Reactive Wells | LNAPL Recovery | Vapor Intrusion Mitigation | Plume Migration Control | Leachate Control | Site Characterization and Sampling

Groundwater Extraction, Extraction of Free-Phase Product, and Dual-Phase Extraction

Adobe PDF LogoMine Tailings Drainage: A Bottoms-up Approach Using HDD Drilling and Installation Methods
Bardsley, D.
Nevada Water Resources Association Annual Conference, Reno NV, February 14-16, 2017.

A gravity-fed dewatering drain was successfully installed via HDD beneath a tailings impoundment containing over 700,000 cubic yards of saturated materials from a former zinc-copper mine. Drilling operations worked downgradient of the impoundment toe, drilling under the tailings pond dam and up into the lower levels of the impoundment. Thorough planning and preparations were necessary to avoid an uncontrollable release of tailings liquids and successfully complete the drain installation.

Adobe PDF LogoFree Product Recovery System Using Horizontal Wells, MCS Cherry Point
Collins, A.
21st Annual International Petroleum Environmental Conference, Houston, Texas. 32 slides, October 13-16, 2014.

Slide presentation describes cleanup of a large plume of free product (aviation fuels) under the active aircraft maintenance building at the Marine Corps Air Station, Cherry Point. Building operations had to continue 24/7 without disruption. A system of three horizontal wells was installed to minimize disturbance to operations and maximize contact with the plume. The wells intersected the plume through long-screened intervals. Hydrophobic pumps pumped free product to a treatment center adjacent to the building. The system effectively removed free product and was recognized by DoD as "free-product recovery system of the year" in 1997.

Adobe PDF LogoSite Characterization, Application and Operation of Horizontal Wells for Ground Water Remediation
Meyer, E.W. and D.S. Bardsley.
Proceedings of the 1996 Petroleum Hydrocarbons & Organic Chemicals in Ground Water: Prevention, Detection, and Remediation Conference, 16 pp, 1996.

A groundwater recovery and treatment system were installed to treat groundwater at the Dow Chemical Company's Louisiana Division manufacturing complex. Reasons for selecting horizontal recovery wells included minimizing interference to plant operations, a more efficient radius of influence in fine-grained soil, and elimination of numerous vertical wells. Paper describes the site, how the wells were constructed, the amount of groundwater and VOCs recovered, a cost analysis, and conclusions.

Adobe PDF LogoHorizontal Wells: An Innovative System
Rawls, G. and D. Oakley.
Horizontal News, Fall 1996.

Horizontal wells were installed at Miami International Airport to extract free product leaking from underground jet fuel lines. An innovative dual-phase extraction system using horizontal wells was designed to maximize recovery. Seven trenches were installed with two parallel wells–one for LNAPL and one for dissolved-phase constituents in groundwater. (See p. 2 of newsletter.)

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Groundwater Recirculation

Bay Road Holdings, East Palo Alto (formerly Romic)
EPA Website.

The primary remedy for the solvent-contaminated groundwater at this Superfund site in California is biological treatment involving a groundwater recirculation system with horizontal injection injection wells and a sugar substrate. The horizontal injection wells, which are over 200 feet long, are used to deliver the substrate into the subsurface. These wells are better able to accurately target contaminated zones and can treat a larger area than standard vertical well points.

Treatment of Chlorinated Aliphatic Contamination of Groundwater by Horizontal Recirculation Wells and by Constructed Vertical Flow Wetlands
Shelley, M.L., M.N. Goltz, J.P. Amon, and A. Agrawal.
AFIT-EN-TR-02-05, 68 pp, 2002.

Technical report explores the remediation of chlorinated ethenes in groundwater by means of horizontal groundwater recirculation wells with downwell zero-valent metal reductive dechlorination reactors and constructed vertical subsurface-flow wetlands. [Abstract]

Field Evaluation of a Horizontal Well Recirculation System for Groundwater Treatment: Field Demonstration at X-701B Portsmouth Gaseous Diffusion Plant, Piketon, Ohio
Korte, N., M. Muck, P. Kearl, R. Siegrist, R. Schlosser, J. Zutman, T. Houk.
Oak Ridge National Lab. ORNL/TM-13529, 173 pp, August 1, 1998.

Report describes the field-scale demonstration with overall goal to evaluate in situ treatment of groundwater using horizontal recirculation coupled with treatment modules. Specifically, horizontal recirculation was tested because of its application to thin, interbedded aquifer zones. Mixed contaminants were targeted because of their prominence at DOE sites and because they cannot be treated with conventional methods. The project involved several research elements, including treatment process evaluation, hydrodynamic flow and transport modeling, pilot testing at an uncontaminated site, and full-scale testing at a contaminated site.

Adobe PDF LogoA Field-Scale Test of In Situ Chemical Oxidation through Recirculation
West, O.R., S.R. Cline, W.L. Holden, F.G. Gardner, B.M. Schlosser, R.L. Siegrist, and T.C. Houk.
Oak Ridge National Lab. ORNL/CP-98459, 9 pp, 1998.

A field-scale test of in situ chemical oxidation through recirculation using a pair of parallel horizontal wells with 200-ft screened sections was conducted at Portsmouth Gaseous Diffusion Plant where groundwater is contaminated with trichloroethene. Successful implementation of in situ chemical oxidation requires an effective means for dispersing the oxidant to contaminated regions in the subsurface. A technique has been developed in which an oxidant is added to extracted groundwater, and the oxidant-laden groundwater is then injected and recirculated into a contaminated aquifer through multiple horizontal and/or vertical wells.

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Air Sparging and Soil Vapor Extraction (SVE)

Ujima Village Apartments/Former Athens Tank Farm
California Regional Water Quality Control Board, Los Angeles Region, GeoTracker Website, 2018.

The 122-acre Athens Tank Farm operated as a petroleum products storage and distribution facility from the 1920s to mid 1960s, and is now occupied by a park, apartment buildings, and some modular buildings. An HRW was installed under the apartment complex in 2015 to pilot test SVE. The HRW was installed to a depth of 30 ft and is 510 ft long with 250 ft of screen. The HRW removed 35 lbs of methane per hour, and a full-scale system was proposed.

Adobe PDF LogoHorizontal Wells for Remediation of Chlorinated Solvent Sites
Carlton, K.J.
47th Annual Environmental Show of the South, Chattanooga, TN, May 16-18, 2018, 33 slides.

Presentation gives an overview of HDD, HRW design, and applications and advantages of the technology. Three projects are detailed, one at a former drycleaner that used 10 horizontal wells for the injection of potassium permanganate and four horizontal wells for SVE.

Adobe PDF LogoPerformance-Based Bioremediation (PBR) at the Former Galena Forward Operating Location (FOL) Alaska
Meeting minutes of the Galena Restoration Advisory Board, October 25, 2017.

Remedies installed in 2017 at the Former Galena Forward Operating Location included two horizontal well air sparge systems: one at the Million Gallon Hill/Missile Storage sites and one at the POL Tank Farm Area/GAVTC Building sites. Each system consists of four wells approximately 1,000 ft long and 40-45 ft deep. See pages 13-24 of the attachment to the minutes for slide presentation that describes these systems.

Adobe PDF LogoActive Vapor Intrusion Mitigation at Pharmaceutical Manufacturer with Horizontal Directional Drilling (HDD) Technology
Iosue, G.N. and M.J. Sequino.
The 10th International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Palm Springs, California. Battelle, Columbus, OH. Poster D-016, May 2016.

HDD was used to advance 2-inch PVC blind horizontal monitoring wells to a target depth of 20 ft below the slab and 120 ft beyond the wall of a pharmaceutical manufacturing facility. The horizontal wells served as compliance monitoring wells and were deployed outside the building with continuous well bores. As part of the vapor intrusion management program, horizontal SVE wells were installed in the vadose zone and thin gravel layer beneath the building to mitigate vapors. Horizontal SVE and monitoring wells were advanced through a 6-inch concrete footer and rock underlying the slab. Advancing the SVE horizontal wells beneath the building actively mitigated the source area to eliminate the vapor intrusion pathway.

Adobe PDF LogoImplementation and Optimization of Air Sparge/Soil Vapor Extraction System with Horizontal and Vertical Wells
Rabideau, T.F., Kinter, B., L.A. Sweet, and D.R. Sopoci.
21st Annual International Petroleum Environmental Conference, Houston, Texas. 32 slides, October 13-16, 2014.

Releases from underground storage tanks containing fuels, waste paints, and solvents at an active manufacturing facility were estimated to affect 0.43 acres of shallow soil and 1.2 acres of perched groundwater. Because soil and groundwater impacts extended beneath the facility, horizontal injection and extraction wells were installed as part of the SVE and air sparging remedial activities to avoid interfering with facility operations. Data from pilot tests, performance monitoring, vapor samples, and perched water samples indicate the system will address remaining impacts and meet cleanup objectives.

Adobe PDF LogoConquering a Busy Intersection to Install Horizontal Remediation Wells and Protect Indoor Air
Sequino, M.
21st Annual International Petroleum Environmental Conference, Houston, Texas. 12 slides, October 13-16, 2014.

A petroleum plume emanating from an automotive service shop at a street corner in Tallahassee, Florida, migrated diagonally across the intersection, inhibiting access to the plume using vertical wells. Curved pathways through multiple buried utility lines were needed for the directional-drilled horizontal well pairs to achieve plume coverage. Downhole sound-locating equipment with continuous calculation of wellbore depths and topographic survey points of the uneven ground surface was used for well placement. Four horizontal air sparging wells were placed along the top of a clay aquitard, with horizontal SVE wells placed with the companion air sparging well for total vapor recovery. The resistance of commercial property owners to the excavation of exit pits on their properties was overcome by installing blind horizontal wells without exit points at the far side of the intersection.

Adobe PDF LogoAir and Ozone Sparging of TCE Using a Directionally Drilled Horizontal Well
Strong, M., C. Bozzini, D. Hood, and B. Lowder.
The 5th International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Monterey, California (May 22-25, 2006).

A one-year pilot test was performed at Camp Lejeune where a horizontal air sparge well was installed below a low-permeability layer for treatment of CVOCs. Extensive lateral distribution of air and rapid reduction of dissolved TCE and associated cVOCs were observed after system startup. Within one year, baseline concentrations of TCE (which exceeded 50 mg/L) decreased by 99% in all monitoring wells. Additional information: Remediation Technology Demonstration project profile Air Sparging through Horizontal Well at Camp Lejeune in North Carolina on EPA's Clu-In.org website (Last updated: July 6, 2007); 2009 article Five additional Technologies Evaluated after ERH Application at Camp Lejeune.

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Bioremediation

Bay Road Holdings, East Palo Alto (formerly Romic)
EPA Website.

The primary remedy for the solvent-contaminated groundwater at this Superfund site in California is biological treatment involving a groundwater recirculation system with horizontal injection wells and a sugar substrate. The horizontal injection wells, which are over 200 feet long, are used to deliver the substrate into the subsurface. These wells are better able to accurately target contaminated zones and can treat a larger area than standard vertical well points. Additional information ISD™ Groundwater Recirculation Pilot System Installation Work PlanAdobe PDF Logo.

Adobe PDF LogoHorizontal Wells for Remediation of Chlorinated Solvent Sites
Carlton, K.J.
47th Annual Environmental Show of the South, Chattanooga, TN, May 16-18, 2018, 33 slides.

Presentation gives an overview of HDD, HRW design, and applications and advantages of the technology. Three projects are detailed, illustrating the use of horizontal wells for ISCO/SVE, groundwater extraction, and bioamendment remediation.

Sitewide Environmental Monitoring Semiannual Progress Report for the Young-Rainey Star Center, June through November 2017
LMS/PIN/N02914, 578 pp, 2018.

To address groundwater contaminated with TCE, DCE, VC, and 1,4-dioxane, injection of emulsified vegetable oil and the microorganism Dehalococcoides mccartyi was conducted in the dissolved-phase plumes on the STAR Center property in October and November 2014, at three offsite properties in February 2015 and February/March 2017, and via four stacked pairs of horizontal wells beneath Building 100 in November 2015 and January/February 2017. Performance monitoring is conducted semiannually.

Adobe PDF LogoMonitoring and Reporting Program No. R5-2015-0012-015 for In-Situ Groundwater Remediation and Discharge of Treated Groundwater to Land for Former John Taylor Fertilizer Co., Stockton, San Joaquin County
Central Valley Regional Water Quality Control Board, 16 pp, 2016.

The June 2015 Remedial Action Workplan presented remedial alternatives and recommended implementing enhanced in situ bioremediation. This approach involves a shallow horizontal injection well spanning across the shallow target area and positioned perpendicular to groundwater flow. For this treatment target area, potable water would be amended with a commercial organic substrate and then injected into shallow groundwater via the horizontal injection well. To promote biodegradation, shallow groundwater will be bioaugmented with a dechlorinating consortium and delivered through the horizontal injection well. Injections via the horizontal injection well are anticipated to create a biologically active zone that transects the shallow groundwater plume. Additional information: GeoTracker website.

Adobe PDF LogoRemedial Action Completion Report (CDRL A001B) and Preliminary Closeout Report, Former Air Force Plant PJKS, Waterton Canyon, Colorado
Air Force Center for Engineering and the Environment, 44 pp, 2013.

The interim corrective measure (ICM) was expanded in 2006 to stimulate anaerobic reductive dechlorination in the D-1 area groundwater plume. A total of 10 horizontal and additional vertical injection wells delivered sodium lactate, emulsified vegetable oil, nutrients, and Dehalococcoides to the aquifer. Upon completion of construction activities, quarterly performance monitoring began in select wells to evaluate the performance of the ICMs in the groundwater source areas.

Adobe PDF LogoInjection of Oxygen in Deep Horizontal Wells for the Biostimulation of PAH Degradation at a Former Wood-Treating Superfund Site
Mott-Smith, E., C. Butler, T. Turner, E. Spalvins, D. Keefer, S.R. Carter.
Proceedings of the Sixth International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Monterey, California, Battelle, 35 pp, June 2011.

In situ bioremediation with aerobic biobarriers was selected in the feasibility study to remedy the extended plume. A pilot study was prepared for beneath the rail yard to evaluate the site-specific oxygen transfer efficiency and effectiveness of the remedy. Three bundled horizontal wells were used to infuse oxygen into the lower permeability zone. The pilot study included pulsing oxygen into the infusion wells during two phases, including a 30-day period in July 2009 and a 90-day period in June 2010.

Adobe PDF LogoPostclosure Groundwater Remediation and Monitoring at the Sanitary Landfill, Savannah River Site: Transitioning to Monitored Natural Attenuation
Ross, J., T. Kmetz, D. Noffsinger, W. Kubilius, and K.M. Adams.
WM'07: Waste Management Conference, Tucson, Arizona, February 25-March 1, 2007. Paper ERD-EN-2006-0176.

From 1997-1998, a biosparging system was constructed to address VOC contamination in groundwater from a sanitary landfill. To intercept contaminants, two horizontal wells were installed in the saturated zone directly south and southeast of the landfill. The horizontal well screens were 800 ft and 900 ft long, and at that time were the longest horizontal remediation wells operating in the U.S. Process monitoring of the biosparging system required a comprehensive sampling network up- and downgradient of the horizontal well system to verify system effectiveness. The scope of monitoring and reporting can be reduced significantly as the objective is to demonstrate that the alternate concentration limits are being met at the point of compliance wells and the maximum contaminant level is being met at the surface water point of exposure. The proposed reduction is estimated to save about $2M over the course of the remaining 25 years of post-closure monitoring.

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Chemical Injection

Segmented Horizontal Well Systems for Targeted Remediation
Piatt, E.
Flash Poster at RemTEC Technology Summit. February 26-28, 2019. Denver, Colorado.

Several case studies will be presented that illuminate the advantages of segmented horizontal well systems, that also incorporate miniaturization and nested bundling methods into the process. [Abstract]

Adobe PDF LogoHorizontal Wells for Remediation of Chlorinated Solvent Sites
Carlton, K.J.
47th Annual Environmental Show of the South, Chattanooga, TN, May 16-18, 2018, 33 slides.

Presentation gives an overview of HDD, HRW design, and applications and advantages of the technology. Three projects are detailed, illustrating the use of horizontal wells for ISCO, groundwater extraction, and bioamendment remediation.

Innovative Deep Horizontal Injection Well Near Full-Scale Pilot Study for Hexavalent Chromium Groundwater Plume – Applications and Lessons Learned
Mason, A., P. Rosewicz, et al.
Eleventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds. April 8-12, 2018.

Abstact for PowerPoint presentation that describes use of 4-inch diameter horizontal injection well for the injection of lactate to promote reduction of hexavalent chromium at the Puchack Well Field Superfund site. Additional information: AbstractAdobe PDF Logo | Slide presentation

Adobe PDF LogoUse of a Deep Horizontal Injection Well for In Situ Hexavalent Chromium Groundwater Plume Treatment – Applications and Lessons Learned
Mason, A., P. Rosewicz, et al.
Eleventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds. April 8-12, 2018.

Poster presentation documents results, challenges, and lessons learned from a pilot test of the 830-foot long horizontal well at Puchack Well Field Superfund site to inject lactate to reduce chromium levels in groundwater at a metal plating site through in situ geochemical fixation.

Adobe PDF LogoPilot Test of a Deep Horizontal Injection Well to Treat Hexavalent Chromium: The Puchack Well Field Superfund Site, Pennsauken, NJ.
Mishkin, K. and J. Gorin.
47 slides. November 27, 2018.

Slide presentation describes a pilot test to reduce the level of Cr6 in groundwater through injection of an unspecified reducing agent into areas of groundwater contamination at the Puchack Well Field Superfund site. Results and lessons learned are discussed.

Adobe PDF LogoUsing 3D Groundwater Visualization to Support Project Management: Application of Leapfrog Hydro at the Puchack Well
Mishkin, K. and J. Gorin.
40 slides. 24th NARPM Training Program, May 2, 2016.

Slide presentation summarizes the use of the 3D visualization tool Leapfrog in making site management decisions and developing 3D figures at the Puchack Well Field Superfund site. The tool was used to optimize the locations of horizontal injection wells. The approach and results are discussed.

Enhanced Delivery of Potassium Permanganate Using Horizontal Wells
Moran, B. and G. Losonsky.
Proceedings of the Sixth International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Monterey, California, Battelle, May 2008.

A major urban high-rise development project in Annapolis, Maryland, required in situ treatment of dry cleaner solvents. Ten horizontal wells were drilled under an active construction site for potassium permanganate injection. The horizontal well system has injected 1.3 million gallons of oxidant solution. Several injection events occurred while high-rise construction continued at the site. Additional information: Slide presentationAdobe PDF Logo.

Adobe PDF LogoA Field-Scale Test of In Situ Chemical Oxidation through Recirculation
West, O.R., S.R. Cline, W.L. Holden, F.G. Gardner, B.M. Schlosser, R.L. Siegrist, and T.C. Houk.
Oak Ridge National Lab. ORNL/CP-98459, 9 pp, 1998.

A field-scale test of in situ chemical oxidation through recirculation using a pair of parallel horizontal wells with 200-ft screened sections was conducted at Portsmouth Gaseous Diffusion Plant where groundwater is contaminated with TCE. Successful implementation of in situ chemical oxidation requires an effective means for dispersing the oxidant to contaminated regions in the subsurface. A technique has been developed in which an oxidant is added to extracted groundwater, and the oxidant-laden groundwater is then injected and recirculated into a contaminated aquifer through multiple horizontal and/or vertical wells.

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In Situ Thermal Treatment

Electrical Resistance Heating

Adobe PDF LogoHorizontal Electrical Resistance Heating for DNAPL Remediation Beneath a Manufacturing Facility
Iosue, G.N. and M.J. Sequino.
The 10th International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Palm Springs, California. Battelle, Columbus, OH. Poster D-016, May 2016.

Electrical resistance heating (ERH) was selected to address a DNAPL plume of PCE and TCE originating from former drycleaning operations and extending to an adjacent property beneath an active manufacturing facility. Horizontal ERH electrodes were installed to minimize disruptions while expediting remediation of impacts beneath the facility. Vertical ERH electrodes were installed in the source area where access and disruption did not pose issues. Both the horizontal and vertical electrodes were designed to operate as a single system while covering the treatment area. Although unforeseen building features, bedrock irregularities, and fill were encountered during horizontal directional drilling, real-time 3-D monitoring and analysis confirmed the design bore path for the horizontal electrode. Stresses on the electrode material, including drilling pressures and radius of curvature, were monitored in real time to ensure no adverse effects. Monitoring data revealed that the horizontal ERH electrode had higher efficiencies and chlorinated solvent reductions than the vertical ERH configuration.

Adobe PDF LogoERH Removes VOC Contaminants under Cold and Low-Permeability Conditions
Ackerman, J.

Technology News and Trends, USEPA Publication EPA 542-N-06-011. 32:4-5(2007).
An electrical resistance heating system that included an array of horizontal vapor extraction wells was used to remediate VOC-contaminated soil and groundwater at a former dry cleaner site in Fargo, North Dakota. A total of 5,188 lbs of VOC mass was removed within the first year of system operation.

Hot Air and Steam Injection

Concluding a Steam Injection Remediation Project at a Dense Non-Aqueous Phase Liquid Source Zone at the Savannah River Site
Kramer, B.J., J. Kupar, J. Ross, J. Cardoso-Neto, D.G. Jackson, B.B. Looney, and K.M. Adams.
WM2015: Waste Management Conference, Phoenix, AZ, March 13-15, 2015. Paper 15303.

Steam injection was selected to remediate the DNAPL source zone at the SRS M-Area Settling Basin in a treatment area with a 3-acre footprint and target depths of 45-165 ft in unconsolidated sand, silt, and clay. The remediation system comprised 96 vertical, horizontal, and angled steam injection and SVE wells, plus a thermal monitoring system. Steam injection was first applied to the deep vadose zone in 2005, progressed to the aquifer zone, and then followed with the mid-vadose zone. Steaming ended in 2009. SVE continued, with residual temperatures in the deep low permeability zones still >150°F, and over 450,000 lbs of VOCs removed by 2015. Assessment of vapor concentrations in the target zone allowed abandonment of one-third of the extraction wells and conversion of another third of the extraction wells to passive solar-operated vapor extraction equipment.

Adobe PDF LogoCase History: Escambia Wood Treatment Superfund Site, Pensacola, FL
Directed Technologies Drilling. 2 pp, 2012.

Fact sheet summarizes work performed to install horizontal steam injection and extraction wells for extracting creosote from the Escambia Wood — Pensacola Superfund site.

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Permeable Reactive Barriers and Biobarriers

Adobe PDF LogoRemedial Action Completion Report (CDRL A001B) and Preliminary Closeout Report, Former Air Force Plant PJKS, Waterton Canyon, Colorado
Air Force Center for Engineering and the Environment, 44 pp, 2013.

The interim corrective measure was expanded in 2006 to stimulate anaerobic reductive dechlorination in the D-1 area groundwater plume. Horizontal and vertical injection wells delivered sodium lactate, emulsified vegetable oil, nutrients, and Dehalococcoides to the aquifer. In 2008, two full-scale biobarriers were constructed via injection of emulsified vegetable oil, sodium lactate, and Dehalococcoides into direct-push boreholes to target the alluvial transition groundwater areas, provide a barrier to plume migration, and further reduce TCE concentrations in the downgradient plume.

Adobe PDF LogoInjection of Oxygen in Deep Horizontal Wells for the Biostimulation of PAH Degradation at a Former Wood-Treating Superfund Site
Butler C., E. Mott-Smith, T.R. Turner, E. Spalvins, S.R. Carter
Proceedings of the Sixth International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Monterey, California, Battelle, 35 pp, June 2011.

In situ bioremediation with aerobic biobarriers was selected in the feasibility study to remedy the extended plume. A pilot study was prepared for beneath the rail yard to evaluate the site-specific oxygen transfer efficiency and effectiveness of the remedy. Three bundled horizontal wells were used to infuse oxygen into the lower permeability zone. The pilot study included pulsing oxygen into the infusion wells during two phases, including a 30-day period in July 2009 and a 90-day period in June 2010.

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Reactive Wells

Non-Pumping Reactive Wells Filled with Mixing Nano and Micro Zero-Valent Iron for Nitrate Removal from Groundwater: Vertical, Horizontal, and Slanted Wells.
Hosseini S.M., Tosco T., Ataie-Ashtiani B., and C.T. Simmons
Journal of Contaminant Hydrology 210(Mar):50-64(2018) [Abstract].

Non-pumping reactive wells (NPRWs) filled by zero-valent iron (ZVI) can be used to remediate groundwater contamination in deep aquifers. Nine batch experiments were performed to investigate the impact of mixed nano-ZVI and micro-ZVI on nitrate removal rate. The wells system was tested in bench-scale sand (60cm length × 40cm width × 25cm height) for three orientations of NPRWs (vertical, horizontal, and slanted).

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

A new in situ remediation concept—the Horizontal Reactive Media Treatment Well (HRX Well®)—uses horizontal wells filled with reactive media to passively treat contaminated groundwater in situ. The approach involves large-diameter directionally drilled horizontal wells filled with granular reactive media generally installed parallel to the direction of groundwater flow. 3D flow and transport simulations showed that capture and treatment widths of up to tens of feet can be achieved for many aquifer settings, and reductions in downgradient concentrations and contaminant mass flux are nearly immediate. See more about the HRX Well technology demonstration and field validation under ESTCP project ER-201631.

Adobe PDF LogoIn Situ Treatment Train for Remediation of Perfluoroalkyl Contaminated Groundwater: In Situ Chemical Oxidation of Sorbed Contaminants (ISCO-SC)
Crimi, M., T. Holsen, C. Bellona, C. Divine, and E. Dickenson
SERDP Project ER-2423, 148 pp, 2017.

The HRX Well™ approach involves installing a large-diameter horizontal well within a contaminant plume, oriented in the general direction of groundwater flow and filled with granular reactive media. ESTCP supported demonstration and field validation of the technology under project ER-201631. Project ER-2423's objective was to develop a predictable and low-cost in situ reactive media treatment train in a horizontal well (technically named in situ chemical oxidation of sorbed contaminants, or ISCO-SC) to remediate groundwater contaminated with per- and polyfluoroalkyl substances (PFAS). In the ISCO-SC treatment train, granular activated carbon (GAC) was used to sorb and concentrate PFAS, followed by contaminant destruction and GAC regeneration in situ using activated persulfide oxidation.

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Vapor Intrusion Mitigation

Adobe PDF LogoActive Vapor Intrusion Mitigation at Pharmaceutical Manufacturer with Horizontal Directional Drilling (HDD) Technology
Iosue, G.N. and M.J. Sequino.
The 10th International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Palm Springs, California. Battelle, Columbus, OH. Poster D-016, May 2016.

HDD was used to advance 2-inch PVC blind horizontal monitoring wells to a target depth of 20 ft below the slab and 120 ft beyond the wall of a pharmaceutical manufacturing facility. The horizontal wells served as compliance monitoring wells and were deployed outside the building with continuous well bores. As part of the vapor intrusion management program, horizontal SVE wells were installed in the vadose zone and thin gravel layer beneath the building to mitigate vapors. Horizontal SVE and monitoring wells were advanced through a 6-inch concrete footer and rock underlying the slab. Advancing the SVE horizontal wells beneath the building actively mitigated the source area to eliminate the vapor intrusion pathway.

Adobe PDF LogoConquering a Busy Intersection to Install Horizontal Remediation Wells and Protect Indoor Air
Sequino, M.
21st Annual International Petroleum Environmental Conference, Houston, Texas. 12 slides, October 13-16, 2014.

A petroleum plume emanating from an automotive service shop at a street corner in Tallahassee, Florida, migrated diagonally across the intersection, inhibiting access to the plume using vertical wells. Curved pathways through multiple buried utility lines were needed for the directional-drilled horizontal well pairs to achieve plume coverage. Downhole sound-locating equipment with continuous calculation of wellbore depths and topographic survey points of the uneven ground surface was used for well placement. Four horizontal air sparging wells were placed along the top of a clay aquitard, with horizontal soil vapor extraction wells placed with the companion air sparging well for total vapor recovery. The resistance of commercial property owners to the excavation of exit pits on their properties was overcome by installing blind horizontal wells without exit points at the far side of the intersection.

Adobe PDF LogoHorizontal Wells for Sub Slab Vapor Intrusion Mitigation and Soil Remediation
Carlton, K.J.
South Eastern States Vapor Intrusion Symposium, Atlanta, GA, February 8-9, 2018. 30 slides.

Presentation provides four examples of horizontal sub-slab mitigation and remediation projects: an office building, a catalytic converter R&D facility, a former auto manufacturing facility, and a former dry cleaner.

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Plume Migration Control

Adobe PDF LogoSand Coulee Acid Mine Drainage Source Control: Abandoned Mine Reclamation Project, Cascade County, Montana and AppendicesAdobe PDF Logo
Montana Department of Environmental Quality (DEQ), Abandoned Mines Section, 144 pp, 2018.

The abandoned mine workings in and around Sand Coulee act as groundwater drains that dewater the overlying Kootenai sandstone and discharge contaminated water to tributaries of Sand Coulee Creek. The acid mine drainage (AMD) is extremely acidic and contains numerous metals, including As, Cd, Cr, Fe, Mn, Ni, Tl, and Zn, at concentrations exceeding Montana DEQ standards. Pilot tests are planned of two methods of reducing flow into the abandoned coal mines: (1) drill horizontally to dewater the Kootenai upstream of the mine workings and discharge clean water to surface water bodies, and (2) drill vertically into the Kootenai aquifer and drain clean water into the lower Madison aquifer, thus reducing the drainage into the abandoned coal mines. The proposed mitigation is source control implemented by intercepting the groundwater in the Kootenai sandstone before it enters the mine workings. This report describes the investigation conducted to identify a location to pilot test a horizontal drainage well and assess the productivity of interception wells and potential reduction in the volume of AMD discharging from nearby mines. The recommendation is for installation of a single horizontal drainage well up to approximately 2,000 ft long and then installation and testing of one to three vertical drainage wells in a subsequent phase of work.

Kelly AFB Tries Horizontal Wells
Walters, D.
ECOTONE 3(4):1999/2000.

Horizontal wells were installed at Kelly Air Force Base, Texas, as an alternative to hundreds of yards of trenching, which would have generated noise and dust in a nearby neighborhood. The goal was to remove enough water from a capture zone near the base boundary to prevent further movement of contamination beyond the fence. The horizontal wells were installed below utilities, avoiding disruption and targeting a thin layer of groundwater.

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Leachate Control

Using Horizontal Extraction Wells to Contain Leachate Plumes Near Landfills
Soukup, W. and W.J. Lee. December 14, 2015.

Webpage describes an 800-foot long horizontal extraction well used to contain a groundwater plume near a landfill at a Superfund site in southern New Jersey. The landfill was operated without a bottom liner and reportedly took in liquid chemical waste at some point in its history.

Environmental Well for Leachate Collection Installed by DTI at Superfund Site in New Jersey
Directional Technologies, Inc.

Case study describes Directional Technologies, Inc. 2014 installation of an 800-foot-long landfill leachate collection well to ensure the protection of offsite potential receptors. The environmental well was designed to be equipped with a pumping system to collect the leachate.

Construction of Horizontal Wells in Municipal Solid Waste Using A Directional Drill
Ho, Pei-Yi Joy.
Master's thesis, University of Waterloo, Ontario, Canada. 118 pp, 2007.

Employing HDD techniques in landfill applications provide several challenges, including unknown waste material density, unknown waste material hardness, and unknown drilling operation and waste material interaction. Conventional HDD studies cannot be directly applied as the drilling medium parameters are virtually unknown. This research incorporated a trial site to gather field data. The trial site is located at the Region of Waterloo Landfill site located on Erb Street in Waterloo, Ontario. The installations took place at the Original Landfill Area, which is currently inactive and capped. The vertical wells, originally installed to control the leachate, have degraded, resulting in inefficient operation of the landfill gas collection system. The field installation of two horizontal wells (in opposing directions) was put in practice not to replace the vertical wells, but to assist in capturing and collecting leachate. The installations were monitored, and key parameters were recorded.

Installation of Horizontal Wells in Landfilled Waste Using Directional Drilling
Cox, S.E., R.P. Beaven, W. Powrie, and D.J. Cole.
Journal of Geotechnical and Geoenvironmental Engineering 132(7):869-878(2006) [Abstract]

In this paper, the feasibility of using directional drilling to install horizontal wells for leachate control in landfills is investigated with reference to pilot- and full-scale field trials at Rainham, U.K. The difficulties of well-screen design and installation in a landfilled waste are discussed; the insights gained during trial installation are described; and the effectiveness of three trial wells is assessed with reference to the leachate flow rates and drawdowns achieved, in comparison with conventional vertical wells.

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Site Characterization and Sampling

Adobe PDF LogoSoil Sampling in "Inaccessible Areas"
Directed Technologies Drilling, Undated.

Two-page fact sheet explains the use of HDD for sampling soil under tanks, buildings, and roads.

Using HDD to Collect Soil Samples Under Obstructions
Bardsley, D.S.
National Driller Magazine, May 2015.

Two brief case studies describe the use of HDD methods to obtain soil samples under buildings, landfills, and other obstructions.

Innovative Investigation Technologies for Coal Tar Impacts Beneath Difficult to Access Areas
Electric Power Research Institute, Palo Alto, CA. EPRI 1019846, 50 pp, 2010.

Document summarizes existing technologies for contaminated site investigations beneath buildings and other limited-access areas at former manufactured gas plant (MGP) sites and identifies potentially applicable innovative technologies, tools, techniques, and approaches that might benefit from pilot-scale field evaluation. Investigative technologies for coal tar and/or DNAPL impacts are identified in the following general categories: 1) drilling technologies; 2) sensors and reactive media; 3) geophysical techniques; and 4) surrogate measures.

Adobe PDF LogoCharacterization of Under-Building Contamination at Rocky Flats Implementing Environmental Measurement-While-Drilling Process with Horizontal Directional Drilling
Williams, C.V., G.J. Lockwood, M.M. Selph, R.A. Normann, and T. Lindsay.
SAND2001-1809, 94 pp, 2001.

The Rocky Flats Environmental Technology Site teamed with Sandia National Laboratories to deploy Environmental Measure-While-Drilling (EMWD) in conjunction with HDD to characterize under-building contamination. The EMWD-gamma ray spectrometer (EMWD-GRS) system provided the capability of producing real-time environmental and drill bit data during drilling operations. This report presents the results of the EMWD-GRS logging of boreholes at two locations, Building 886 and Building 123. Additional information: Rocky Flats HDD/EMWD Fact SheetAdobe PDF Logo

Environmental Measurement-While-Drilling System and Horizontal Directional Drilling Technology Demonstration, Hanford Site
Williams, C.V., G.J. Lockwood, R.A. Normann, D.A. Myers, M.G. Gardner, T. Williamson, and J. Huffinan.
SAND99-1479, 140 pp, 1999.

The technology demonstration consisted of the development of one borehole under a mock waste tank at a depth of 27 ft, following a predetermined bore path, tracking the bore path to within a radius of 5 ft, and monitoring for zones of radiological activity using the Environmental Measurement-While-Drilling (EMWD) system. A second borehole was advanced to demonstrate the capability of drilling to a depth of 70 ft, the depth needed to obtain access under the Hanford waste tanks and continue drilling horizontally. This report presents information on the horizontal directional drilling and EMWD technologies, demonstration design, results of the demonstrations, and lessons learned.

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