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In
Situ Remediation using Horizontal Wells
The Need
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Underground fuel storage tanks have become a
nightmare for thousands of businesses, including contractors. Leaking tanks will
contaminate soil and groundwater not only at owner's site, but also beneath adjoining
property. Remediation using traditional methods of access, such as vertical wells directly
over the plume, disrupts activities on the site, and sometime access directly over the
contamination is impossible. The cost of such method is also considered high. |
Ditch Witch, a directional drilling equipment from
the Charles Machine Works
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The Technology
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Horizontal well technology has been widely used
in petroleum and underground utility installation. Since late 1980's, the technology has
been adapted for environmental remediation applications. The method of drilling the horizontal well can begin in vertically or
directionally at the ground surface and then proceeds horizontally to a depth and length
depending on desired installation parameters. Two general methods in drilling
horizontal wells have been used in remediation, trenched and directionally-drilled. The
first method involves the excavation of a relatively large diameter borehole, with
simultaneous installation of well materials and backfill. The second method, directional
drilling, produces a smaller diameter borehole and well materials are installed following
the completion of drilling activities. |
Navigator, a directional drilling equipment from the
Vermeer Manufacturing Company |
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 Materials that can be used for
well screen and casing for horizontal wells are the same as the materials used for
vertical wells. Axial strength, tensile strength, and flexural strength are factors that
should be considered in selecting materials for horizontal wells. Various types of
materials that have been used include:
- Fiber reinforced plastic (FRP)
- Fiberglass reinforced epoxy(FRE)
- High density polyethylene (HDPE)
- High temperature polyethylene (HTPE)
- Polyvinyl chloride (PVC)
- Stainless steel
- Porous polyethylene well screen
This technology can be used in the application of various
remediation techniques such as ground-water and/or non-aqueous phase liquid extraction,
air sparging, soil vapor extraction, in situ bioremediation, in situ flushing, treatment
walls, hydraulic and pneumatic fracturing, etc. This technology is very useful when
contaminant plume covers a large area and has linear geometry, or when surface
obstructions are present.
The costs of horizontal well installation varies depending on
many site specific factors, the range is from $25-$85 per foot, while the average cost of
horizontal directional drilling for regular utility installation is between $10 - $20 per
foot. |
The Benefits
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- Horizontal well screens contact a larger surface area of
contaminated media thereby enhancing remediation of a greater volume of contaminated media
per well.
- Horizontal wells need less wells than vertical wells.
- A horizontal well configuration allows better access
to/contact with linear plumes.
- Installation can be completed with minimal disturbance to
surface operations.
- Directionally drilled horizontal well can be installed under
building and other obstructions.
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Status
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Over 300 horizontal wells have been installed
for environmental remediation in US. Horizontal well technology has been accepted by the
EPA, DOD, DOE, the New Jersey-New York Port Authority, the petrochemical industry, and
most state environmental regulators. The leaders in developing remediation procedures for
directional boring equipment are, among others, the Charles Machine Works, Inc. (CMW)
which manufactures Ditch Witch underground construction equipment and Vermeer
Manufacturing Company which produces Navigator directional boring machines. |
Barriers
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Based on the technology overview report of
Ground-Water Remediation Technologies Analysis Center (GWRTAC) on horizontal wells,
limitation of trenched wells include:
- This method needs disposal of contaminated soil which is
considered to be expensive
- Inability to be installed beneath building due to potential
instability resulting from undercutting.
- Installation lengths may be limited by underground utility
lines since precise steering around such obstacles is not possible.
- Well installation cannot proceed in hard rock
General limitation of horizontal wells:
- Not applicable for light non-aqueous phase liquid (LNAPL)
recovery in area with large water table fluctuations.
- Well installation depths can be limited.
- Vertical capture zone is limited by the vertical hydraulic
conductivity, which is usually significantly lower than horizontal conductivity.
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Points of Contact
- Audrey Branson, The Charles Machine Works, Inc, Perry, OK
73033, Phone: 800-654-6481 and 405-336-4402, Fax: 405-336-3458
- David D. Wilson, Horizontal Well & Environmental
Consultants, LLC, Arvada, Colorado, Phone: (303) 422-1302
- Doug Hundt, Vermeer Manufacturing Company, P.O. Box 200,
Pella, Iowa 50219, Phone: (515) 628-3141, Fax: (515) 621-7734
References
- David D. Wilson, Advanced Environmental Horizontal Wells:
Design, Procurement, and Installation, NGWA Outdoor Action Conference Workshop Handout,
Las Vegas, 1995
- Directional Boring Comes of Age, Constructor, August 1995
- Ditch Witch The Underground Authority Online, the Charles Machine Works, Inc. http://www.ditchwitch.com/
- George Losonsky and David S. Bardsley, Horizontal Wells Offer
Advantages in Environmental Remediation, Trenchless Technology, November 1997
- Horizontal Well Technology and Information, http://www.horizontalwell.com/
- Horizontal Wells, Technology Overview Report, TO-96-02,
GWRTAC, Pittsburgh, October 1996, http://www.gwrtac.org/html/tech_over.html#HORIZWELL
- Hybrid Directional Boring and Horizontal Logging, Pacific
Northwest National Laboratory, United States Department of Energy, http://www.pnl.gov/WEBTECH/mwlid/dirdrill.html
- Louis B. Fournier, Getting the Lowdown on HEWs, Directional
Drilling, February 1999.
- Navigator Directional Boring Machines: The World Leader,
Vermeer Manufacturing Company,
http://www.vermeer.com/equipment_main/trenchless/directional_boring.htm
- Trenchless Remediation, Constructor, August 1995
Disclaimer Statement
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Neither the Construction
Industry Institute nor Purdue University in any way endorses this
technology or represents
that the information presented can be relied upon without further investigation. |
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