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Remediation Technologies Screening Matrix, Version 4.0 4.35 Directional Wells
(In Situ GW  Remediation Technology)
  Description Synonyms Applicability Limitations Site Information Points of Contact
Data Needs Performance Cost References Vendor Info. Health & Safety
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>>3.10 In Situ Physical/Chemical Treatment

      >>4.35 Directional Wells
Introduction>> Drilling techniques are used to position wells horizontally, or at an angle, to reach contaminants not accessible by direct vertical drilling.

Description:

Figure 4-35:
Typical Diagram of In Situ Air Stripping with Horizontal Wells  

Drilling techniques are used to position wells horizontally, or at an angle, to reach contaminants not accessible by direct vertical drilling. Directional drilling may be used to enhance other in-situ or in-well technologies such as ground water pumping, bioventing, SVE, soil flushing, and in-well air stripping.

Hardware used for directional boring includes wireline coring rigs, hydraulic thrust systems, electric cone penetrometers, steering tracking hardware, sonic drilling, and push coring systems. Hydraulically activated thrust equipment capable of exerting more than 40 tons of thrust is used to push the directional boring heads into the earth. Directional control is obtained by proper positioning of the face of the nonsymmetric boring head. Slow rotation of the boring head will cut and compact the geologic material into the borehole wall. Thrusting a boring head that is not rotating will cause a directional change. The machinery is capable of initiating a borehole, steering down to a desired horizontal depth, continuing at that depth, and then steering back to the surface at a downrange location.

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Synonyms:

Horizontal Wells.

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Applicability:

Directional well technology is applicable to the complete range of contaminant groups with no particular target group. It is particularly useful when existing structures interfere with placement of vertical wells.

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Limitations:

Factors that may limit the applicability and effectiveness of the process include:
  • The potential exists for the wells to collapse.
  • Specialized equipment is required.
  • Wells are difficult to position precisely.
  • Installation of horizontal wells is typically costly.
  • Currently, the technology is limited to depths of less than 50 feet.

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Data Needs:

A detailed discussion of these data elements is provided in Subsection 2.2.2. (Data Requirements for Ground Water, Surface Water, and Leachate).

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Performance Data:

Testing was performed as part of the Mixed Waste Landfill Integrated Demonstration at Sandia National Laboratories, Albuquerque, NM. Several directional holes were drilled; a depth of 12 meters (40 feet) was achieved with a maximum horizontal extent of 174 meters (570 feet).

A DOE field demonstration at the Savannah River site was performed in FY90 for in situ air stripping (ISAS), a mass transfer process that uses horizontal injection and vacuum extraction wells to remediate sites contaminated with VOCs within the vadose zone and soil/ground water in the saturated zone. Air is injected into the saturated zone through horizontal injection wells placed below the water table. As the air passes through the contaminant plume, it volatilizes the chemical constituents. This process performs best in homogeneous soil conditions, while heterogeneities such as formations, fractures, clay layers, and partial clay lenses hinder performance. Clay layers often have high contaminant concentrations, while stratigraphy can cause preferential flow paths and limit the process efficiency. ISAS has been shown to be effective when some interbedded, thin, and/or discontinuous clays are present. A full-scale demonstration, including 4% methane enhancement as a bioremediation nutrient in the injection well, was conducted during FY92, with results to be available in FY93. Better underground transport modeling and bioremediation modeling are needed. The technology was also used successfully in the DOE VOCs in the Non-Arid Soils Integrated Demonstration in Savannah River, South Carolina. Testing of directional boring for monitoring equipment installation was performed in an actual contamination zone during the summer of 1992.

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Cost:

Estimated costs are about $60 to $250 per meter ($20 to $75 per foot) for hydraulic bi-directional thrust drilling. Sonic drilling can be as much as $330 per meter ($100 per foot). Costs for installing a PVC or HDPE well using a small to medium sized utility-type drilling rig are projected as $164/m ($50/ft).

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References:

Innovative Remediation Technologies:  Field Scale Demonstration Project in North America, 2nd Edition

Abstracts of Remediation Case Studies, Volume 4,  June, 2000, EPA 542-R-00-006

Guide to Documenting and Managing Cost and Performance Information for Remediation Projects - Revised Version, October, 1998, EPA 542-B-98-007

DOE, 1991. Horizontal Hybrid Directional Boring, FY92 Technical Task Plan, TTP Reference No.: AL-ZU23-J2.

DOE, 1991. SRS Integrated Demonstration: Directional Drilling, FY92 Technical Task Plan, TTP Reference No.: SR-1211-01.

DOE, 1992. Directional Sonic Drilling, FY93 Technical Task Plan, TTP Reference No.: AL-2311-05.

DOE, 1993. Directional Boring and Thrusting with Hybrid Underground Utility Industry Equipment, ProTech Database, TTP References: AL2211-16 and AL2211-03.

DOE, 1994. Technology Catalogue, First Edition. February.

DOE, 1993. Technology Name: Slant-Angle Sonic Drilling, Technology Information Profile (Rev. 2), DOE ProTech Database, TTP Reference No.: AL2310-05.

EPA, 1994. Manual: Alternative Methods for Fluid Delivery and Recovery, Prepared by: Murdoch, L., and Wilson, D.D. EPA/625/R-94/003.

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

Kaback, D., and Oakley, D. 1996. "Horizontal Environmental Wells in the United States: A Catalogue," Colorado Center for Environmental Management (CCEM).

Wilson, D.D., and Kaback, D.S., 1993. "Industry Survey for Horizontal Wells", Westinghouse Savannah River Company (DOE), Aiken, SC. WSRC-TR-93-511.

Wilson, D.D., 1996. "Use of Horizontal Drilling In Environmental Remediation: A Horizontal Well Case Study", Water Well Journal, February.

Wilson, D.D., 1996, "Horizontal Well Development Made Easy", Water Well Journal, October.

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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 Water 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:

Hazard Analysis

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