This page provides links to case studies of fracturing applications, beginning with resources where multiple case studies using different fracturing techniques have been compiled. The next section contains site examples where blasting was used as the fracturing technique. The following sections discuss hydraulic and pneumatic fracturing and are divided into two sub-sections: recovery assistance (e.g. for P&T and SVE systems) and in situ amendment applications. Induced fracturing for recovery assistance has been used to improve environmental applications since the late 1980s. With the increased use and success of amendments for in situ site remediation, more recently fracturing techniques are enabling the extension of amendment use to less permeable soil and bedrock applications. Note: EPA NPL site descriptions generally do not provide detailed descriptions of the fracturing technology only that it was used. For detailed information it may be necessary to contact the RPM directly. RPM contact information is provided in the general site information URL.

Case Study Compilations

In Situ Remediation Technology Status Report: Hydrofracturing/Pneumatic Fracturing
EPA 542-K-94-005, 1994

This report describes field demonstrations or full-scale applications of in situ abiotic technologies for nonaqueous phase liquids and groundwater treatment.

Technology Status Report: Hydraulic, Pneumatic and Blast-Enhanced Fracturing
Roote, D.
Ground-Water Remediation Technologies Analysis Center, 173 pp, 2000

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Environmental Hydraulic Fracturing

Recovery Assistance

Centre County Kepone, State College Borough, PA

Superfund NPL site. Hydraulic fracturing was used to increase the recovery of the SVE system in the overburden soils at the Tank Farm area

• The 2009 Five-Year Review provides a brief description of the system
• More general site information

Greenwood Chemical Co., Newtown, VA

Superfund NPL site. Hydraulic fracturing was used to increase the extraction efficiency of groundwater extraction wells placed in fractured bedrock. Contamination of groundwater consisted primarily of volatile organic compounds including 1,2-dichloroethane, carbon tetrachloride and vinyl chloride, semi-volatile organic compounds including naphthalene and bis (2-chloroethyl) ether.

• The 2008 Five-Year Review provides a brief description of the system.
• More general site information

Innovative Remediation Techniques In Complex Lithologies
Forkheim, Terry and Gordon Bures
Global Land Reclamation/Remediation 2000 and Beyond, Edmonton, Alberta - September 16-21, 2000

This paper presents the approach and results of a remedial action at the former Corbett Creek Gas Plant. The contaminants of concern were dissolved and free phase hydrocarbons. Hydrofracturing was used to increase the permeability of the on-site soils to facilitate groundwater and condensate recovery.

Linemaster Switch Corp., Woodstock, CT

Superfund NPL site. Hydraulic fracturing was used to increase efficiency of dual vacuum extraction system. It was not successful over the long term.

• The 2009 Five-Year Review provides a brief description of the system.
• More general site information

McGraw Edison, Centerville, IA

Hydrofracturing was used to enhance the performance of an SVE system. The SVE system construction was completed in early 2000 and consisted of nine pairs of fracture enhanced extraction points. Each SVE pair included a shallow extraction point and a deep extraction point. The average depth of the shallow points is six feet below ground surface (bgs), and the depth of the deep points ranges from 19.5 to 24.5 feet bgs. Horizontal hydrofracturing was performed using 12,111 gallons of a sand gel mixture to enhance air flow in the soil.

• The 2009 Five-Year Review provides a brief description of the system.

Amendment Application

A Rigorous Demonstration of Permeability Enhancement Technology for In Situ Remediation of Low Permeability Media
Sorenson, K., D. Nguyen, R. Wymore, and N. Smith.
ESTCP Project ER-201430, 651 pp, 2019

A hybrid pneumatic permeability enhancement technology was pilot tested to facilitate amendment delivery and distribution at 3 sites with low-permeability lithologies: Marine Corps Base-Camp Pendleton (MCB-CP), Lake City Army Ammunition Plant (LCAAP) Site 17D, and the Grand Forks Air Force Base (GFAFB) site TU594. The overall objective was to compare the performance and cost benefits of hydraulic and hybrid pneumatic permeability enhancement for in situ treatment at low-permeability sites. Advanced geophysics monitoring tools evaluated the vertical and horizontal extent of amendment distribution, and measurements were validated by conventional soil confirmation and groundwater performance monitoring. The technology achieved 99-100% of the target injection within the treatment areas at MCB-CP and GFAFB, and 70% at LCAAP despite challenging subsurface conditions. A cost comparison exercise indicated that permeability enhancement techniques can be more or significantly more competitive than conventional injection techniques.

A-Zone Aquifer ZVI Permeable Reactive Barrier Project, Hookston Station Site, Pleasant Hill, California: Final Construction Report
GeoSierra Environmental, Inc.
California Regional Water Quality Control Board, San Francisco Bay Region. 45 pp, Sep 2009

An iron PRB was installed in 2009 at an off-site location near the Hookston Station site to degrade TCE, cis-1,2-DCE, VC, and 1,1-DCE in site groundwater and limit their migration downgradient. Constructed using azimuth-controlled vertical hydrofracturing technology, the PRB consists of one continuous reactive zone of ZVI ~480 feet in length and ~32 feet in vertical height. Additional information: 2017 Status report ; CRWQCB Project Page

Achieving Successful In Situ Remediation of Petroleum Impacted Clays Using Permeable Treatment Pathways Emplaced by Hydraulic Fracturing
Frac Rite Environmental, Ltd.
REMTECH 2010: The Remediation Technologies Symposium, Banff, AB, Canada, 20-22 Oct 2010. Environmental Services Association of Alberta, Edmonton, AB (Canada), 20 slides, 2010

Hydrofracturing of clay soils with sand emplacement to hold fractures open and calcium peroxide for slow release oxygen was conducted at a petroleum tank storage facility. The hydrofracturing was followed by injection of stabilized hydrogen peroxide into four of the five fracture boreholes as a direct contaminant oxidant.

Active Manufacturing Site Northern Area, NJ

Note: The geology consists of Triassic-aged, low permeability siltstone and shale bedrock. Porosity is estimated at 1-4%. Groundwater flow appears to be controlled by horizontal bedding fractures and the regional strike direction. Approximately 800 lb of nanoscale ZVI was injected into the shallow PCE source area in Nov-Dec 05. In order to improve hydraulic communication and the ability to distribute ZVI throughout the source area, fracturing was performed prior to ZVI injection. Performance monitoring of the ZVI injection indicated significant impacts on source area geochemistry, including increased pH levels (~9) and low ORP values (-500 mV).

Bioremediation of Chlorinated Solvents in Variably Saturated, Low Permeability Soils: Final Report
Lebow, P.S. and R.C. Starr.
Appendix F (p 72-107) in the Third Five-Year Review Report for Distler Brickyard, West Point, Hardin County, Kentucky.
NW-2005-021, 36 pp, 2005

A pilot study was conducted to evaluate the combination of hydraulic fracturing for enhancing permeability of fine-textured soil and emplacement of chitin for stimulating bioremediation of chloroethenes at the Distler Brickyard site. The project was funded in part by a National Science Foundation SBIR grant. [Note: A copy of the final report submitted to NSF is attached as Appendix F to the 2008 5-year review report.] Results include:

• The mixture of chitin and sand was readily injected into the fine-textured soil at the site using hydraulic fracturing.
• TCE was degraded sequentially to DCE, VC, and ethene in both the lab and field experiments. Hence, emplacing chitin into the subsurface is an effective technique for stimulating biodegradation of chloroethenes.
• The field results indicate that chitin acted as a source of volatile fatty acids in the subsurface for 8 to 12 months.

Distler Brickyard, West Point, KY

Superfund NPL site. Hydraulic fracturing of a silt and clay was used to place chitin for enhanced bioremediation.

• The 2008 Five-Year Review provides a description of the system.
• More general site information

Evaluation of Enhanced VOC Removal with Soil Fracturing in the SRS Upland Unit
Riha, B.D., K. Dixon, W.K. Hyde, L. Murdoch, and R. Hall.
WSRC-TR-2005-00415, 53 pp, 2005

Pilot-scale tests were conducted in July 2005 at DOE's Savannah River site to evaluate the effectiveness of using hydraulic fracturing as a means to improve SVE system performance. Four sand-filled fractures in the Upland Unit accelerated SVE solvent remediation and increased flow rates by at least one order of magnitude.

Evaluation of the Propagation of Secondary Fractures from Hydraulic Fracture and Injection to Create a Treatment Zone in Low Permeability Fractured Clay Soils
Peace, C. and L.M. Austrins.
REMTECH 2010: The Remediation Technologies Symposium, Banff, AB, Canada, 20-22 Oct 2010. Environmental Services Association of Alberta, Edmonton, AB (Canada), 29 slides, 2010

At the site of a chemical production plant in operation since the 1950s, the subsurface was contaminated with a variety of chlorinated VOCs (unspecified). A soil fracturing and injection pilot study was carried out in a low-permeability, fractured silty clay till to introduce slow-release amendment into secondary fractures and create a remedial diffusion halo into the surrounding low-permeability clay till. Quantifying the propagation and relative location of secondary fractures, as well as determining the effective treatment zone, was a primary metric for successful application. A total of six locations at three depths, 12, 15, and 18 ft bgs were fractured, and a mixture of guar, ZVI, glycol, and breaker solution was injected. Effective emplacement in the treatment area occurred and was quantified spatially. This successful pilot allowed for the optimization of fracture geometry before implementation at a larger scale, and the technique has been applied to several other areas of the site.

F.E. Warren Air Force Base, Cheyenne, WY

Superfund NPL site. Hydrofracturing in soil was used to place sand and potassium permanganate at SS7. The network of fracture location/injection points for both the shallow and middle zone consists of:

• An estimated 150 shallow-zone and 12 middle-zone fracture initiation locations,
• Several hundred pounds of solid KMnO4 and sand per fracture and
• Solution of bioaugmentation culture for each fracture location.

The chemical oxidation and subsequent MNA have proven effective in reducing TCE contamination in groundwater and should remain effective in the long term in combination with the LUCs that are also in the Final Plan.

• The 2008 Five-Year Review provides a description of the system.
• More general site information
• Geophysical Imaging for Investigating the Delivery and Distribution of Amendments in the Heterogeneous Subsurface of the F.E. Warren AFB
• ESTCP Cost & Performance Report

FRTR Cost and Performance Case Studies

Former Villa Italia Mall Lakewood , CO

To enhance electron donor delivery, bulk hydraulic conductivity at the site was increased via a hydrofracturing program. In addition, the hydrofracturing program was designed to quickly release organic carbon into the subsurface, establishing the proper environment for reductive dechlorination. The hydrofracturing was performed using a pneumatic straddle-packer assemblage and fracturing rig capable of producing up to 450 pounds per square inch (psi). A total of 57 locations were fractured and two to three zones were fractured per location. Surface monitoring (tilt meter and depth to water measurements) indicate the radius of influence from each fracture ranged from 35 to greater than 70 feet.

Fracture-Emplacement and 3-D Mapping of a Microiron/Carbon Amendment in TCE-Impacted Sedimentary Bedrock (Abstract)
Bures, G., J.A Skog, D. Swift, J. Rothermel, R. Starr, and J. Moreno
Seventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Monterey, CA; May 2010)

An in situ pilot remediation project was carried out on behalf of the U.S. Army Corps of Engineers (Omaha District) at the F.E. Warren Air Force Base Former Atlas E Missile Site No. 12 in Colorado. Between 6,000 and 32,000 lbs of microiron/carbon amendment was emplaced at each borehole by mixing it as a biodegradable, linear protein gel slurry to carry the amendment in a uniform suspension. Hydraulic fracturing was conducted in 9 pre-drilled boreholes to deliver the amendment slurry at 5-ft increments between depths of 35 to 63 ft in bedrock. Hydraulic fracturing was successful in emplacing greater than 98% of the total design mass of 205,550 lb. of EHC-G™ zero valent micro-iron/carbon within TCE-impacted bedrock sediments across an area of approximately 64,000 ft2. The implications of this work are that massive quantities of micro-iron (or other) amendments can be cost-effectively emplaced in challenging geologic environments (e.g., deep bedrock) to treat large plume areas using few injection borings.

Hydraulic Fracturing Technology: Technology Evaluation Report
EPA 540-R-93-505, 147 pp, 1993

This report describes the development, demonstration, and evaluation of the hydraulic fracturing technology developed by the University of Cincinnati and EPA's Risk Reduction Engineering Laboratory. During 1991 and 1992, two pilot-scale demonstrations were conducted under EPA's SITE Program at a Xerox Corporation SVE site in Oak Brook, IL, and at a bioremediation site near Dayton, OH.

The hydraulic fracturing technology was demonstrated in 1991 and 1992 at the Xerox Oak Brook site, where SVE was being conducted. On-site soil contamination included ethylbenzene; l,l-dichloroethane (DCA); trichloroethene (TCE); tetrachloroethene (PCE); 1, 1, 1-trichloroethane (TCA); toluene; and xylene. The vapor flow rates, soil vacuums, and contaminant yields of two hydraulically fractured and two unfractured wells were compared. The fractured wells were fractured at 6, 10, and 15 ft bgs. The vapor yield from fractured wells was one order of magnitude greater than from unfractured wells. This higher yield was obtained in an area 30 times greater than the area affected by the unfractured well. The contaminant mass recovery from fractured wells was 7 to 14 times greater than that from the unfractured well.

The pilot-scale demonstration at the Dayton site was conducted in 1991 and 1992. Site contamination included benzene, toluene, ethylbenzene, and xylene (BTEX); and total petroleum hydrocarbons (TPH). Fractures were created at 7, 8, 10, and 12 ft bgs at one of two on-site wells. Water containing hydrogen peroxide and nutrients was pumped into the hydraulically fractured well and into one unfractured well 50 ft from the fractured well. The injection rates, soil moisture contents, microbial metabolic activity, numbers of colony forming units (CFU), and rates of bioremediation at the fractured and unfractured wells were compared. In the fractured well, the injection rate was 25 to 40 times greater, and moisture content increased 2 to 4 times near the fracture. Comparison of microbial metabolic activity, CFU, and rates of bioremediation were inconclusive.

In Situ Remediation Technology Status Report: Hydrofracturing/Pneumatic Fracturing
EPA 542-K-94-005, 1994

This report describes field demonstrations or full-scale applications of in situ abiotic technologies for nonaqueous phase liquids and groundwater treatment.

In Situ Treatment of Chlorinated Volatile Organic Hydrocarbons by Fracture-Emplacement of a Micro-Iron/Carbon Amendment
Skog, J., D. Swift, J. Rothermel, R. Starr, G.H. Bures, and J. Moreno.
REMTECH 2009: The Remediation Technologies Symposium, Banff, AB, Canada, 14-16 Oct 2009. Environmental Services Association of Alberta, Edmonton. 25 presentation slides, 2009

An in situ pilot remediation project was carried out on behalf of the U.S. Army Corps of Engineers (Omaha District) at the F.E. Warren AFB in Colorado. The pilot featured an innovative application of drilling, fracture emplacement, treatment, and geophysical technologies to mitigate impacts from chlorinated solvents. The former missile site complex is underlain by silty sandstone bedrock sediments affected by TCE >2,000 µg/L and associated VOCs. Pilot tests of biotic and abiotic in situ chemical reduction (ISCR) were conducted in the source area and dissolved plume to evaluate technology performance prior to developing the proposed remedy. The pilot involved the emplacement of over 100 tons of EHC™, a micro-iron/complex-carbon treatment amendment, into deep bedrock sediments to attain optimal distribution throughout the contaminant plume, including beneath the former Launch and Service Building. The radius of fracture emplacement in the bedrock was up to 60 ft, with a typical fracture overlap of 30 to 50%. Following placement of the amendment, physical, chemical, and microbiological processes combined to create very strong reducing conditions that stimulated chemical and microbiological dehalogenation of the contaminants. View longer abstract.

Methods for Enhanced Delivery of In Situ Remediation Amendments in Contaminated Clay Till
Camilla Maymann Christiansen, Ph.D. thesis, Technical University of Denmark, Kgs. Lyngby, ISBN: 978-87-91855-88-7, 86 pp, 2010

A field study was conducted at a site in Denmark from March 2006 to March 2010 to test and document the capabilities of three enhanced delivery methods—pneumatic fracturing, hydraulic fracturing, and direct-push delivery—in clay till at depths of 2.5 to 9.5 m bgs. The focus was on the extent of delivery of in situ remediation amendments in clay till rather than on the treatment of the contaminants or the efficacy of the amendments developed for their treatment. Direct documentation at depth was largely confined to coring but was supplemented by excavation at shallow depths.

The study demonstrated that hydraulic fracturing functioned well at 3 mbs. However, attempts to emplace horizontal (closely-spaced) fractures at 6-7 and 9.5 mbs. were unsuccessful. Induced pneumatic fractures (4-8 mbs.) were initially horizontal, but prone to diversion in natural (vertical) fractures in the sediment. Close networks of fractures at each fracturing depth were not observed. However, discrete, closely-spaced fractures may be obtainable if a smaller spacing is implemented between fracturing intervals. Direct-push delivery was successful in creating closely-spaced, horizontal substance deliveries at all tested depths (2.5-3.5, 6-7, and 8.5-9.5 mbs.).

Unresolved issues that remain. For pneumatic and hydraulic fracturing the main unresolved issues are: 1) the lower limits of fracture spacing at depths greater than 5 mbs., and 2) the ability of these technologies, especially hydraulic fracturing, to create subhorizontal fractures at depths greater than 5 mbs. For direct-push delivery, the influence of delivery volumes on delivery orientation, form, and radius is unclear.

Multiphase Approach to Remediation Using Subsurface Fracturing, Surface Extraction and Modified Fenton Chemistry
Owens, D.C., Oxy Teknologies.
REMTECH 2010: The Remediation Technologies Symposium, Banff, AB, Canada, 20-22 Oct 2010. Environmental Services Association of Alberta, Edmonton, AB (Canada), 14 slides, 2010

ISCO with modified Fenton chemistry in conjunction with subsurface fracturing and surface extraction was conducted to remediate 11,325 cubic meters of diesel- and gasoline-contaminated soil and groundwater at a trucking terminal operated 24 hour per day without disrupting terminal operations. Free-phase liquid petroleum hydrocarbons (LPH) covered an area extending ~1,100 square meters. Subsurface fracturing was effective in about half the contaminated area and showed no significant results in the other half. Costs were high compared to the added value of the fracturing. The unpredictability of fracturing routes and fracture diffusion also are problems with this technology. Surface extraction of LPH was limited by cold surface conditions, limited fracturing effectiveness, and seasonality of the water table; overall, the method gave results equal or superior to pump and treat at significantly lower costs. ISCO with stabilized hydrogen peroxide was very effective in degrading the LPH in free, dissolved, and absorbed phases. The limiting factor was the ability to get the oxidant into contact with the LPH due to the tight soil conditions. Working conditions were difficult. Undermining the asphalt during ISCO was an ongoing problem but was handled with spot repairs. Winter conditions were also a limiting factor because of the difficulty of locating injection wells in snow and ice. The methods used in this remediation project resulted in cost savings of roughly $2.3 million when compared to standard dig and haul, plus an additional $3.6 million in potential relocation and lost business costs for a total savings of $5.9 million. In 10 months of treatment, the average thickness of LPH decreased 94%, while total dissolved-phase PHCs fell by 96%, demonstrating that a multi-phased remediation approach can provide remediation without disruption to an operating facility.

Oxidant Dispersal in Tight Clay Formations Using EK3 Technology
Frisky, S.
REMTECH 2010: The Remediation Technologies Symposium, Banff, AB, Canada, 20-22 Oct 2010. Environmental Services Association of Alberta, Edmonton, AB (Canada), 46 slides, 2010

EK3 is a process in which a low-voltage DC electric field is applied across a section of clay soil to disperse a water/chemical oxidant mixture within the formation, primarily via electroosmosis. Combining EK3 technology with injection wells, clay fracturing, and injection of chemical oxidant can increase the efficiency and effectiveness of chemical oxidant dispersion significantly. In a pilot project located in Regina (Canada), the EK3 technology was used to disperse a water/chemical oxidant mixture throughout a test plot of tight clay soil to treat hydrocarbon contamination. In addition to hydrocarbons remediation, the technology can be used to address contaminating salts and metals as described in an article posted by National Research Council Canada.

Remediation of DNAPLs in Low Permeability Soils: Innovative Technology Summary Report
2000. U.S. DOE, Office of Environmental Management, Subsurface Contaminants Focus Area. Report No: DOE/EM-0550, 36 pp.

This report provides a description of a comparative field demonstration of hydraulic fracturing to enhance mass recovery or emplace reactive barriers that was conducted during the fall of 1996 through the spring of 1998 at the Portsmouth Gaseous Diffusion Plant (PORTS) X-231A land treatment site. The demonstration treated chlorinated solvents (specifically TCE) in both the vadose and saturated zones within low permeability silt and clay deposits.

Sharpe Army Depot, Lathrop, CA

Superfund NPL site. To potentially shorten the time of P&T operation, the site has conducted two hydraulic fracturing pilot studies. One used potassium permanganate to address more contaminated plume areas and the other used EHC™ (carbon source with ZVI).

• The 2009 Five-Year Review provides a brief discussion of the system.
• More general site information

X-231A Demonstration of In-Situ Remediation of DNAPL Compounds in Low Permeability Media by Soil Fracturing with Thermally Enhanced Mass Recovery or Reactive Barrier Destruction
1998. R.L. Siegrist, et al. ORNL/TM--13534, NTIS: DE98058134, 300 pp.

A set of four test cells was established at the X-231A land treatment unit in August 1996, and a series of field activities occurred through December 1997 to demonstrate soil fracturing with thermally enhanced mass recovery or horizontal barrier destruction in situ.The following remediation technologies were evaluated in the test cells: Cell A - steam injection; Cell B - hot air injection; Cell C - iron metal permeable reactive barrier; and Cell D - potassium permanganate oxidation.

In Cell A, a highly heterogeneous distribution of contaminant mass and low levels of contaminants precluded a thorough evaluation of process efficiency.

For Cell B, hot air injection increased the rate of contaminants removed by volatilization, with off-gas containing more than 800 ppmv of TCE and up to 17% methane.

For Cell C, the iron proppant remained active (30-40% initial degradation of TCE) for up to 27 months after placement, but with little effect to surrounding soil.

For Cell D, the permanganate was more active (>99% degradation of TCE within 2 hours) and created zones of reactive soil that continued to grow away from the fracture over a 27 month period.

Environmental Pneumatic Fracturing

Recovery Assistance

Accutech Pneumatic Fracturing Extraction and Hot Gas Injection, Phase I: Applications Analysis Report
U.S. EPA, Risk Reduction Engineering Laboratory, Cincinnati, OH.
EPA 540-AR-93-509, 56 pp, 1993

This demonstration project evaluated the removal of TCE from vadose zones of low permeability at an industrial park in Somerville, NJ, using the Accutech Remedial Systems' Pneumatic Fracturing Extraction℠ process (SVE). The project also evaluated the effects, in terms of heat transfer and VOC mass removal, of hot gas injection into the formation.

Conclusions from the demonstration included:

• Pneumatic fracturing does introduce additional fractures into this shale formation and/or enlarges and extends existing fractures, thereby extending the vacuum radius of influence significantly. Extracted air flow through the formation is increased considerably more than the 100% claimed by the developer.
• Largely as a result of the increased extracted air flow rate, and perhaps due to accessibility of new pockets of VOCs, the mass removal rate for trichloroethene also is increased far in excess of the 50% claimed by the developer.
• Specifically, based on 4-hr extraction tests, prefracture air flows of <0.017 m3/min (0.6 scfm) increased to 0.112 to 0.168 m3/min (4.0 to 6.0 scfm) or an average increase of 600%.
• Access to and removal of other VOCs also appears to be improved, since elevated concentrations (and masses) not found in the prefracture extraction test were found in the extracted air after fracturing
• Based on extraction tests from peripheral monitoring wells, average air flow rates were increased from 700% to 1,000% in wells at a 10 ft distance, and 200% to 900% in wells 20 ft from the fracture well.
• With radially placed wells open as passive air inlets significantly higher extracted air flow rates (19,500% increase) were obtained after fracturing and the TCE mass removal rates also were increased (2,300%).
• With proper selection and characterization of a site, pneumatic fracturing extraction should be well suited to the treatment of vadose zones of low permeability containing a wide range of VOC pollutants.

Former PVC Manufacturing Facility, New Jersey

Pneumatic fracturing to assist a dual phase extraction system. Full scale remediation began in 1995 with pneumatic fracturing and dual phase extraction (DPE). Twenty extraction wells were installed. The area of treatment was 1.5 acres and the depth of treatment was 30 ft.

The DPE was successful in removing the bulk mass of contamination and bringing the dissolved TCE concentrations down to the single digit ppm levels. At this point, the system was considered inefficient and costly as the mass removal had asymptotic levels.

Johnson & Johnson,Vicellon, SC

Pneumatic fracturing to aid in pump and treat and SVE. Pneumatic fracturing was very effective in opening up dead end fractures, providing interconnection between wells and greatly increasing the yield. At some locations, up to 400 psi. were needed to create crosshole flow between wells. Many wells yields were increased from less than 1 gpm. to greater than 10 gpm. To prevent potential drag down of contaminants from shallow zones, the DNAPL source area was dewatered in stages. After several months of free phase pumping and hi-vacuum dewatering, the main portion of the DNAPL mass was removed and localized drawdowns of up to 80 ft. were achieved. Forced hot air injection and vapor extraction were very effective. Crosshole hot air/water flushing through fractures was effective in recovering immobile DNAPL, especially when using air preheated to >1000 degrees F. By increasing the temperature of the target zone from 60 degrees to >250 degrees, increased PCE vapor concentrations, and thus recovery rates by 20 times. In less than 30 days PCE concentrations in one of the primary wells decreased 97% from greater than 4,000 µg/L to less than 100 µg/L. Temperatures of purge water from the primary well remained at or near 240 degrees for several days and 160 degrees for several weeks following the test.

LaSalle Electric Utilities, La Salle, IL

Superfund NPL site. Pneumatic fracturing of soil was used to increase the efficiency of SVE and P&T systems. Installation of dual phase SVE units in the Laboratory area and in the Thinner Shed area was completed in January 2003, and the startup and shakedown period took place during February 2003. By pneumatically fracturing the site soils, an increase in the hydraulic conductivity of the remediation areas was achieved, and groundwater extraction was significantly increased.

• The 2004 Five-Year Review provides a brief discussion of the system.
• More general site information

Loring Air Force Base, Limestone, ME

Superfund NPL site. Pneumatic fracturing in overburden soils for increased bioventing efficiency. In 2008, pneumatic fracturing was successfully performed across the site to increase the permeability of site soils and thereby enhance the bioventing system influence. Either 1 or 2 fracturing intervals were conducted at each location, as field conditions allowed. Following the pneumatic fracturing event, 14 of the proposed fracture locations were converted to additional air injection wells.

• The 2010 Five-Year Review provides a brief discussion of the system.
• More general site information

Tinker Air Force Base (Soldier Creek/Building 3001), Oklahoma City, OK

Superfund NPL site. Pneumatic fracturing was conducted to enhance product recovery (fuel) in fractured rock at the NTA. Free product removal began on May 26, 1991. Recovery of floating fuel has been accomplished by a number of methods, including bailing, product-only pumping, dual fluid, and total fluids (product and water) pumping. In addition, pneumatic fracturing of the aquifer was performed in 1993 to enhance product recovery.

• The 2002 Five-Year Review provides a brief discussion of the system
• More general site information

Amendment Application

1,1,1-TCA at an Unknown Industrial Facility

Prior to ZVI delivery, fracturing was performed under gas pressures of up to 650 pounds per square inch (psi). During June and September 2006, 13,100 pounds of ZVI was injected in conjunction with Pneumatic Fracturing to position a commercially available sponge ZVI (H-200). ZVI was introduced into a 15-foot thick bedrock zone in 3 to 3.5-foot sections and isolated by high-pressure packers. The ZVI was delivered under pressures that ranged between 60 to 280 psi with a maximum of 550 psi. Approximately 50% of the treatment zone did not have ZVI injected because the bedrock was competent.

Over 12 months, TCA, 1,1-DCA, and 1,1-DCE concentrations within the source zone were decreased by 90%. Downgradient well concentrations of TCA and 1,1-DCE have decreased by 85% and 75% respectively, though 1,1-DCA concentrations increased.

Chloroform and TCE Reduction Using Pneumatically Injected Microscale Zero-Valent Iron (ZVI)
Forman, K., M. Kito, H. Kayaci, J. Zimmerle, D. Rhoades, and C. Silver
Seventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Monterey, CA; May 2010)

This paper and presentation reports on a large field-scale treatability study (45,000 sq ft) of ZVI using pneumatic fracturing of soil at the Hunters Point shipyard. The first step in the ZVI injection process was pneumatic fracturing using high-pressure nitrogen gas to create or widen fractures in soil. The fracturing was followed by ZVI injection as either a water-based slurry or as a dry powder. The ZVI injection effectively remediated the TCE and chloroform groundwater plumes beneath the target parcels below the groundwater remediation goals.

Cost and Performance Report: Nanoscale Zero-Valent Iron Technologies for Source Remediation
A. Gavaskar, L. Tatar, and W. Condit
Environmental Security Technology Certification Program, CR-05-007-ENV, 54 pp, 2005.

NZVI field demonstrations were conducted at three sites: Hunters Point Shipyard (pneumatic fracturing using nitrogen as the carrier gas for iron slurry injection in TCE cleanup), Naval Air Station Jacksonville (direct push of iron slurry with recirculation for TCE), and Naval Air Engineering Station Lakehurst (direct push of iron slurry for TCE).

The Navy conducted considerable performance monitoring at the three sites and the key results are summarized in this report.

• At Hunters Point, two ZVI injection studies were conducted, one in the source area and the other in the plume. In the first study, 16,000 lb of micron-sized ZVI powder was made into a 265 g/L iron slurry in tap water and was injected into the DNAPL source zone by pneumatic fracturing, using nitrogen as the carrier gas. The iron-to-soil ratio achieved in the target treatment zone was 0.004. After injection, ORP of the groundwater dropped to below −500 mV and pH rose above 8, indicating that strongly reducing conditions suitable for abiotic dehalogenation of TCE were generated. There was no significant formation of cis-1,2-DCE immediately after injection, thus indicating that microbially driven anaerobic reduction was not the primary mechanism for TCE mass removal. Longer-term monitoring over one year after injection showed some signs of a rebound (increase) in ORP and DCE in some wells, thus indicating that the ZVI was losing some reactivity. However, TCE levels continued to remain low and the DCE rebound subsided eventually, thus indicating that ORP remained reducing enough to promote biodegradation and hydrogenolysis of residuals.
• In the second injection study at Hunters Point, 72,650 lb of microscale ZVI was made into a 300-g/L slurry in tap water and was similarly injected by pneumatic fracturing into a region of more dilute contamination next to the DNAPL source. The iron-to-soil ratio achieved was 0.001. After ZVI injection, ORP dropped to below −400 mV in one well, but was between −200 mV and −400 mV in other wells. Compared to the first study, ORP started rebounding more quickly after the second injection. Persistence of DCE and VC in the treatment zone after the second injection study is another indicator that insufficient iron may have been injected to generate the strongly reducing conditions necessary to stimulate the more efficient abiotic (beta-elimination) reactions that were created in the first study. However, the mildly reducing conditions generated were sufficient to promote hydrogenolysis and anaerobic biodegradation of TCE.
• At NAS Jacksonville, 300 lb of BNP from PARS Environmental Inc. was made into a 4.5- to 10-g/L iron slurry with water from an extraction well and injected into the subsurface by a combination of direct push and closed-loop recirculation wells. After injection, groundwater ORP dropped to below −200 mV, but pH remained relatively constant. The levels of cis-DCE rose significantly, indicating that anaerobic biodegradation and hydrogenolysis were significantly stimulated, but aquifer conditions may not have been reducing enough to stimulate abiotic reduction (beta-elimination) of TCE and other CVOCs. Either the iron was partially passivated before injection when mixing with relatively high volume of oxygenated water to form the injection slurry or the iron-to-soil ratio was not high enough to generate the strongly reducing conditions necessary for abiotic reduction (beta-elimination).
• At NAES Lakehurst, 300 lb of BNP from PARS Environmental Inc. was made into a relatively dilute 2-g/L slurry with water from an extraction well (Northern Plume) and from a fire hydrant (Southern Plume) and injected into the subsurface by direct push. After injection, there was no change in ORP and pH. In fact, ORP increased in some wells. Either the iron was passivated before injection when mixing with a relatively high volume of oxygenated water to form the injection slurry or the iron-to-soil ratio was not high enough to generate the reducing conditions necessary to stimulate either anaerobic microbial degradation or abiotic reduction. TCE, cis-DCE, and VC levels gradually decreased in the monitoring wells over several weeks of monitoring. The increase in ORP and the decrease in CVOC concentrations may be indicative of dilution of contamination due to the injection of 18,000 gallons of oxygenated water into the treatment zone.

The report also contains a lessons learned section.

Enhancing In Situ Bioremediation with Pneumatic Fracturing
Anderson, D.B., B.M. Peyton, J.L. Liskowitz, C. Fitzgerald, and J.R. Schuring.
Third International Symposium: In Situ and On-Site Bioreclamation, 24-27 April 1994, San Diego, CA. PNL-SA-24717, 14 pp, 1994

Pneumatic fracturing technology was demonstrated at two field sites at Tinker AFB, Oklahoma City, OK, to increase permeability of the subsurface (fine-grain silts, clays, and sedimentary rock) for more effective bioventing and to improve recovery of free-product fuel. Post-fracture airflows were 500 to 1,700% higher than pre-fracture airflows for specific fractured intervals in the formation. Fracturing also increased free-product recovery rates of No. 2 fuel from an average of 587 L (155 gal)/month before fracturing to 1,647 L (435 gal)/month afterward.

FRTR Cost and Performance Case Studies

Ferox℠ Injection Technology Demonstration, Parcel C, Remedial Unit C4, Hunters Point Shipyard, San Francisco, California: Cost and Performance Report
Naval Facilities Engineering Command, 64 pp, 2003

Ferox℠ technology involves injection of liquid atomized ZVI powder into targeted subsurface zones. The technology was demonstrated at Hunters Point Shipyard (Nov 2002-March 2003) using pneumatic fracturing as a first step prior to injection to promote movement of the ZVI through the subsurface and contact with contaminants.

Following ZVI injection, strongly reducing conditions in groundwater were observed out to a radius of 15 feet from each of the four injection boreholes. Within this 15-foot radius, which was considered to be the area of full treatment, the average oxidation-reduction potential was reduced to -372 millivolts. The depth of the treatment zone was estimated to extend from the top of the water table (about 7 feet bgs) to 32 feet bgs. Thus, the treated area covered approximately 1,818 square feet, and the treated subsurface volume was approximately 1,683 cubic yards. Based on 12 weeks of groundwater monitoring results following ZVI injection, near complete, reductive dechlorination of all chlorinated VOCs was achieved. Reduction of TCE, the predominant contaminant, to ethene and chloride was rapid and nearly complete, with a reduction of 99.2 percent within the treatment zone. No significant increases in TCE degradation intermediates (such as cis-1,2-dichloroethene and vinyl chloride) were observed. Significant rebound of chlorinated VOC concentrations did not occur even as of the last sampling event, which was 3 months after ZVI was injected. A statistical analysis of changes in contaminant concentrations outside of the treatment zone further supports the conclusion that TCE destroyed rather than displaced as a result of the injections. Thus, it was concluded that the Ferox℠ injection technology provided effective in situ remedial treatment of the source zone of chlorinated VOCs at this site.

The total cost of the field-scale implementation of the Ferox℠ injection technology at RU-C4 was $289,274, or $172 per cubic yard of the treatment zone. Excluding costs for sampling, analysis, and management of demonstration-derived wastes, the total cost was $196,665, or $117 per cubic yard. Economies of scale for certain cost elements, such as mobilization and demobilization, could result in somewhat lower unit costs for larger-scale applications.

Former Manufacturing Facility, Northern NJ

Pneumatic fracturing with atomized slow release substrate was used at this site. Between 1,000 - 4,000 µg/L of tetrachloroethene was measured in the shallow bedrock below a former dry well. A pilot test for the selected remedy consisted of three injection wells and one monitoring well. Lateral substrate distribution was facilitated through the use of packers which isolated 4 to 5 fracture zones within each injection well. Horizontal substrate distribution was facilitated through the use of ARS Technologies' patented Pneumatic Fracturing and Liquid Atomized Injection technology. Each fracture zone was treated with 60 to 75 gallons of dilute Slow Release Substrate (SRS) and was immediately followed with an equal volume of atomized chase water. The radius of influence was measured at 35-feet by both real-time data as well as post-injection measurements. Dissolved oxygen and oxidation/reduction potential reductions indicated anaerobic conditions at 90 feet in the down-gradient groundwater and bedrock strike direction. Three months after injection, bioaugmentation was performed.

Sixty days after SRS injection, groundwater data indicated anaerobic groundwater conditions that were favorable for reductive dehalogenation in a 30,000 square foot area around the injection wells and within the top 40 feet of the aquifer. Shallow bedrock monitoring wells located in the top 20 feet experienced: (1) a minimum of 90% tetrachloroethene reduction, (2) minimal generation of trichloroethene, 1,2-dichloroethene, and vinyl chloride, and (3) 150-200% increases in hydrogen concentrations. Similar groundwater chemistry improvements were seen in the deep wells in the same area.

Former Naval Surface Warfare Center, White Oak - OU19 Silver Spring, MD

Pneumatic fracturing followed by injection of emulsified oil substrate

From May 7 through June 3, 2007, pneumatic fracturing was performed to increase subsurface permeability and was followed by the injection of emulsified oil substrate into forty-five boreholes. Pneumatic fracturing pressures ranged from 60 to 700 pounds per square inch. Within a 60,000 square foot treatment area, approximately 10,440 pounds of 60% oil substrate was injected into the boreholes with a substrate injection pressure range of 35 to 260 pounds per square inch. Following injection of the emulsion, 57 gallons of chase water was injected. Monitoring of the substrate distribution, persistence and treatment effectiveness took place via five existing monitoring wells located within 30 feet of the injection points.

Immediately following injection, visual inspection of groundwater monitoring samples and measurement of elevated total organic carbon confirmed initial substrate distribution. Within six months of injection, samples for all treatment-area wells indicated that PCE concentrations had decreased below 5 μg/L. Notable rebound in contaminant concentrations was seen in two of the monitoring wells in the treatment zone (one was located 40 feet downgradient and the other was 20 feet cross gradient).

Former PVC Manufacturing Facility, New Jersey

Pneumatic fracturing to disperse ZVI powder using the FEROX technology. A pilot test for applying Ferox technology, which is based on a specialty ZVI powder integrated with a gas-based injection method, was carried out. The ZVI powder was injected into three existing open-rock wells using nitrogen gas as a carrier fluid. The volume flow rate and the velocity of the nitrogen gas "atomized" the ZVI slurry and dispersed it uniformly. The iron was injected into depths from 12 ft bgs to approximately 27 ft bgs.

Based on field observation and pressure monitoring, the injection process was a success in dispersing the Ferox powder into the target zone. Results, after four rounds of post injection sampling, revealed significant TCE reduction in most of the monitoring wells. Concentrations decreased from as high as 3,700 µg/l to non-detect.

Installation of Permeable Reactive Barriers Using Pneumatic Fracturing
Schnell, D.L.
American Chemical Society Preprints of Extended Abstracts 40(1):1114-1119(2001)

Pneumatic fracturing can be implemented to install dry media, such as ZVI and sand, to create a PRB. This paper describes the planning and results of a treatability test for a site in California with consideration of the size of the iron, the quantity of ZVI needed to achieve reduction, and potential changes to groundwater flow rates arising from fracturing.

Manufacturing Site, New York

Pneumatic fracturing to assist DNAPL recovery and introduction of bioremediation amendments.

Marine Corps Logistics Base, Albany, GA

Pilot studies were performed at the Northern Plume Area (NPA) using sodium lactate delivered via hydraulic fracturing and hydrogen sparging into a well that was pneumatically fractured to determine if enhanced bioremediation would effectively meet the contamination reduction goals in the OU 6 Record of Decision (ROD). The pilot studies revealed that hydraulic fracturing and sodium lactate delivery into the subsurface was difficult due to the subsurface soil type and the high viscosity of the sodium lactate. The pilot studies also showed that the pneumatic fracturing and hydrogen sparge was not very effective because the fractures "healed" and the hydrogen could not be delivered over a long enough period of time to enhance the biological degradation. Due to the problems encountered with the enhanced bioremediation pilot studies, additional pilot studies were conducted at the Depot Maintenance Activity (DMA) plume area. These pilot studies both used pneumatic fracturing followed by immediately pumping zero-valent iron (ZVI) and potassium permanganate into an injection boring. The ZVI pilot study revealed that the contaminants could be quickly destroyed upon contact with the ZVI, but that due to the density of the ZVI particles they could only be distributed approximately 25 feet from the injection boring. The potassium permanganate pilot study showed that the contaminants could be quickly destroyed upon contact, and that the radius of influence was approximately 50 feet from the injection boring. However, the potassium permanganate could not destroy carbon tetrachloride. Based on the pilot studies an Explanation of Significant Differences was prepared that changed the OU 6 ROD to use ZVI in plume areas contaminated with carbon tetrachloride, and permanganate in plume areas contaminated with trichloroethene and daughter products.

• The 2006 Five-Year Review provides a discussion of the system
• More general site information

USN Naval Surface Warfare Center-White Oak, Silver Spring, MD (2007)

From January 10, through February 3, 2005, ARS Technologies Inc. conducted pneumatic fracturing and zero valent iron (ZVI) injection into injection wells (IW)-l through IW-15. A total of 77,150 pounds of ZVI mixed with 23,506 gallons of water were injected into the subsurface at Site 5/13. Based on the elevated pressure readings in the monitoring wells, pneumatic fracturing and ZVI emplacement were successful.

The monitoring data indicate that the ZVI injection has significantly reduced the contaminant concentrations. For 4 of the 6 chemicals of concern, the concentrations have met the PRGs. Perchloroethane (PCA) has shown the greatest reduction in concentration, which is to be expected because PCA was the source compound. There was a significant reduction in contaminant concentrations between Aug 04 and Feb 05 indicating a direct relationship between ZVI injection and contaminant reduction.

Using Pneumatic Fracturing for In-Situ Remediation of Contaminated Sites
Schuring, J.R., P.C. Chan, and T.M. Boland.
Remediation Journal 5(2):77-90(1995)

This paper provides a general description of the pneumatic fracturing concept and, apparatus, and key technological considerations, such as fracture initiation, fracture orientation, fracture flow, and treatable soils and contaminants. Three case studies describe different pneumatic fracturing applications: extraction of methylene chloride and TCA from clay; extraction of TCE from bedrock; and recovery of fuel oil from stratified deposits.

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Blast Enhanced Environmental Fracturing

Blast Fracturing: Installation and Evaluation of a Fractured Bedrock Zone within Granitic Bedrock at Edwards AFB
Henkes, M., S. Grossi, D. Britton, and P. Hallman.
Fractured Rock Conference: State of the Science and Measuring Success in Remediation, September 24-26, 2007, Portland, Maine. 298-311(2007)

This paper describes a pilot study involving creation of two fractured bedrock zones (Northern and Southern FBZs) at Site 37, Edwards AFB, CA. Groundwater occurs in discrete water-bearing zones within fractured granitic bedrock at low yields (<0.1 gallons per minute [gpm] and ~0.3 gpm in the two study areas) that limit remedial options. The blasting events did not increase groundwater yields and the paper discusses potential reasons why and suggests actions that could be taken to achieve better results.

Eastman Kodak Company-Kodak Park Rochester, NY

,The general remediation approach that has been used at this site is hydraulic containment of all groundwater on site. Groundwater recovery methods in use include overburden french drains, conventional pumping wells, hydrofractured bedrock wells, and fractured bedrock trenches created through controlled blasting (using explosives on-site to create rock fractures). Recovered water is treated at Kodak's wastewater treatment plant.

• EPA contact information

FMC Corporation Middleport, NY

The groundwater pump and treat system at this site includes recovery from several extraction wells placed in trenches that have been blasted into the bedrock to enhance groundwater yields. These blasted bedrock trenches run along most of the northern and eastern property boundary lines. The groundwater pump and treatment system includes 14 wells.

• EPA contact information

Modern Landfill York County, PA

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