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Remediation Technologies Screening Matrix, Version 4.0 4.6 Fracturing
(In Situ Soil Remediation Technology)
  Description Synonyms Applicability Limitations Site Information Points of Contact
Data Needs Performance Cost References Vendor Info. Health & Safety
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Technology>>Soil, Sediment, Bedrock and Sludge

>>3.2 In Situ Physical/Chemical Treatment

      >>4.6 Fracturing
Introduction>> Cracks are developed by fracturing beneath the surface in low permeability and over-consolidated sediments to open new passageways that increase the effectiveness of many in situ processes and enhance extraction efficiencies.

Description:

Figure 4-6: Typical Pneumatic Fracturing Process Fracturing is an enhancement technology designed to increase the efficiency of other in situ technologies in difficult soil conditions. The fracturing extends and enlarges existing fissures and introduces new fractures, primarily in the horizontal direction. When fracturing has been completed, the formation is then subjected to vapor extraction, either by applying a vacuum to all wells or by extracting from selected wells, while other wells are capped or used for passive air inlet or forced air injection. Technologies commonly used in soil fracturing include pneumatic fracturing (PF), blast-enhanced fracturing and LasagnaTM process.

Blast-enhanced Fracturing

Blast-enhanced fracturing is a process used at sites with fractured bedrock formations. The increased well yields, hydraulic conductivity values, and capture zones occur as a result of the highly fractured area created by detonation of explosives in boreholes.

LasagnaTM Process

LasagnaTM is an integrated, in situ remedial technology, which combines electroosmosis with treatment zones that are installed directly in the contaminated soil. In LasagnaTM process, hydraulic fracturing is used to create sorption/degradation zones horizontally in the subsurface soil.

Pneumatic Fracturing (PF)

In the PF process, fracture wells are drilled in the contaminated vadose zone and left open (uncased) for most of their depth. A packer system is used to isolate small (0.6-meter or 2-foot) intervals so that short bursts (~20 seconds) of compressed air (less than 10,300 mmHg or 200 pounds per square inch) can be injected into the interval to fracture the formation. The process is repeated for each interval within the contaminated depth.

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Synonyms:

DSERTS Code: M15 (Pneumatic Fracturing Enhancement).

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Applicability:

Fracturing is applicable to the complete range of contaminant groups with no particular target group. The technology is used primarily to fracture silts, clays, shale, and bedrock.

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Limitations:

Factors that may limit the applicability and effectiveness of the process include:
  • The technology should not be used in areas of high seismic activity.
  • Fractures will close in non-clayey soils.
  • Investigation of possible underground utilities, structures, or trapped free product is required.
  • The potential exists to open new pathways for the unwanted spread of contaminants (e.g., dense nonaqueous phase liquids).

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Data Needs:

A detailed discussion of these data elements is provided in Subsection 2.2.1 (Data Requirements for Soil, Sediment, and Sludge). Soil characteristics that need to be determined include the depth and areal extent of contamination, the concentration of the contaminants, and soil type and properties (e.g., structure, organic content, texture, permeability, water-holding capacity, and moisture content).

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Performance Data:

The technology is currently available from only one vendor. PF was tested with hot gas injection and extraction in EPA's SITE demonstration program in 1992. Results indicate that PF increased the effective vacuum radius of influence nearly threefold and increased the rate of mass removal up to 25 times over the rates measured using conventional extraction technologies. A Phase II demonstration is planned for 1994. The technology has been demonstrated in the field, including the one under EPA's SITE program. In addition, numerous bench-scale and theoretical studies have been published.

During the summer of 1993, a pilot demonstration of pneumatic fracturing was sponsored by DOE at Tinker AFB to enhance remediation of the fine-grained silts, clays, and sedimentary rock that underlie the site. At one test area, where No. 2 fuel oil was being pumped from existing recovery wells, pneumatic fracturing increased the average monthly removal rate by 15 times. Tests conducted in the unsaturated zone also showed enhanced air permeability as a result of fracturing, ranging from 5 to 30 times greater than prefracture values.

Normal operation employs a two-person crew, making 15 to 25 fractures per day with a fracture radius of 4 to 6 meters (15 to 20 feet) to a depth of 15 to 30 meters (50 to 100 feet). For longer remediation programs, refracturing efforts may be required at 6- to 12-month intervals.

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Cost:

The approximate cost range for pneumatic fracturing is $9 to $13 per metric ton ($8 to $12 per ton).

Cost for LasagnaTM is estimated at $180 to $200 per metric ton ($160 to $180 per ton) for remediation in 1 year, $110 to $130 per metric ton ($100 to $120 per ton) if 3 years are allowed for remediation.

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References:

Link to the U.S. Environmental Protection Agency's Technology Innovation Office (TIO) website which contains information related to identifying and remediating contaminated fractured rock sites.

Athmer, C. J. et al., 1996, Large Scale Field Test of Lasagna Process, Remediation Technologies Development Forum Topical Report, DOE/METC/31185-5390, DE97002156.

California Base Closure Environmental Committee (CBCEC), 1994. Treatment Technologies Applications Matrix for Base Closure Activities, Revision 1, Technology Matching Process Action Team, November, 1994.

EPA, 1993. Accutech Pneumatic Fracturing Extraction and Hot Gas Injection, Phase I, EPA RREL; series includes Technology Evaluation, EPA/540/R-93/509; Technology Demonstration Summary, EPA/540/ SR-93/509; Demonstration Bulletin, EPA/540/MR-93/509; and Applications Analysis, EPA/540/AR-93/509.

EPA, 1993. "Pneumatic Fracturing Increases VOC Extractor Rate," Tech Trends, EPA Report, EPA/542/N-93/010.

EPA, 1995. In Situ Remediation Technology Status Report: Hydraulic and Pneumatic Fracturing, EPA/542/K-94/005.

EPA, 1996. LasagnaTM Public-Private Partnership, EPA Report EPA/542/F-96/010A.

EPA, 1997. Analysis of Selected Enhancements for Soil Vapor Extraction, EPA OSWER, EPA/542/R-97/007.

Federal Remediation Technologies Roundtable, 1997. Remediation Case Studies: Bioremediation and Vitrification, EPA/542/R-97/008.

Federal Remediation Technologies Roundtable, 1997. Remediation Case Studies: Soil Vapor Extraction and Other In Situ Technologies, EPA/542/R-97/009.

Miller, R. R., 1996. Artificially-Induced or Blast-Enhanced Fracturing, Ground-Water Remediation Technologies Analysis Center, Technology Overview Report TO-96-01.

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Site Information:

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Points of Contact:

General FRTR Agency Contacts

Technology Specific Web Sites:

Government Web Sites

Non Government Web Sites

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Vendor Information:

A list of vendors offering In Situ Physical/Chemical Soil Treatment  is available from EPA REACH IT which combines information from three established EPA databases, the Vendor Information System for Innovative Treatment Technologies (VISITT), the Vendor Field Analytical and Characterization Technologies System (Vendor FACTS), and the Innovative Treatment Technologies (ITT), to give users access to comprehensive information about treatment and characterization technologies and their applications.

Government Disclaimer

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Health and Safety:

To be added.

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