DTI  has been implementing horizontal drilling projects for environmental clients for the past 20 years.  Our clients and partners include environmental consultants, Fortune 500 companies, federal agencies, and small businesses.   Please call Dr. John Collins at (203) 836-4445 or email jcollins@directionaltech.com for more information.
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The above article was written by John Collins, Ph D, a new addition to the Directional Technologies, Inc. team. Dr. John Collins is the Vice President of Technology and Product Development and Principal Scientist at Directional Technologies, Inc. He is responsible for developing new technologies around horizontal well technology. He is also responsible for partnerships with technology companies and for developing synergistic relationships between new product companies and DTI.

Dr. John Collin states:

“I joined Directional Technologies, Inc. because I believe that Horizontal Remediation Wells (HRW) are a better way to deliver treatment such as SVE, ISCO, S-ISCO, thermal and other environmental treatment (nanoparticles, reductants, etc.). They provide more contaminant contact and solve many of the transport and physics problems with in-situ environmental remediation.  There is a bright future for the development of remedial technologies specifically for horizontal remediation wells.”

Site Background

Dream Hub is a massive $40 billion redevelopment project in the heart of Seoul, South Korea encompassing an international business district spanning over 34 million square feet and hosting what is to be the tallest building in Asia, thus, landing Seoul on the map of cities with the world’s tallest skyscrapers.  This substantial urban development will span over 140 acres and will include an international business district, residential neighborhoods, world-class retail centers, cultural institutions, educational facilities, along with major transportation hubs intermixed with large urban parks adjacent to the Han River.  The site for this redevelopment formerly served as the rail yard foundry and locomotive maintenance center for Korea Rail (KORAIL) for over 100 years, which through the years, has resulted in significant environmental impacts to both soil and groundwater throughout the site.

The Solution

As part of the remedial effort, Directional Technologies, Inc., partnering with AMEC   Environmental & Infrastructure and IS2B were retained by Samsung C&T, a subsidiary of Korea’s largest conglomerate, to serve as the lead horizontal remediation well technical consultant. Directional Technologies provided the horizontal engineering designs, well materials and worked with an in-country directional utility drilling contractor to install over 1,100 meters (3,300 feet) of horizontal piping, at an average depth of 4.5 meters (14.8 feet).  Due to the aggressive time frame of the redevelopment project schedule, the field effort had to take place within a narrow window with subzero temperatures not recorded in Seoul in over 55 years.  Although the local Korean utility contractor had no experience in installing slotted screen material or with environmental related projects, Directional Technologies provided the critical technical guidance and know-how to successfully install all six horizontal remediation wells within a one-week time period, on time and within budget.

Each horizontal well will be connected to dedicated 40 HP, high-vacuum, oil sealed liquid ring pumps as part of a multiphase extraction system to collect both free product and organic contaminants within the soil vadose zone in order to minimize the potential health risks to workers during the planned large-scale site excavation phase.  The application of horizontal wells for an environmental remedial approach has never been successfully applied in the Republic of Korea.  Directional Technologies’ horizontal wells at Yongsan are the first-of-its-kind application in Korea as part of a high vacuum, multiphase extraction system.

Faced with a variety of subslab problems, environmental managers are turning to horizontal drilling technology at a growing number of commercial building sites across the United States.  Engineered horizontal well screens can achieve multiple objectives, including:

• Vadose zone source removal,
• Reduction of soil gas concentrations,
• Subslab depressurization, and
• Soil moisture control

Vapor mitigation and soil source removal represent the primary concern at environmental sites where volatilization of hydrocarbons at the water table or in the vadose zone can affect indoor air quality.  At other sites, the main objective of subslab air removal is dehumidification to address moisture-related problems in the building floor.  One such site is an office building in Raritan, New Jersey in which the building floor had chronic problems with wet spots in the floor that were caused by excessive moisture buildup in the subslab soils.

Horizontal driller installing horizontal well screens under building

The Horizontal Well Screen System

The 100-by-300-foot office building was built on compacted sand backfill.  Utility line depths and water table fluctuations indicated an optimal depth range for a horizontal extraction well screen between 1 ½ and 3 ¼ feet below the base of the building slab.  A vertical soil vapor extraction (SVE) well pilot test provided the vacuum and flow rate range for the system, but the zone of influence of the horizontal well screen was estimated based on Directional Technologies’ data and experience from horizontal SVE wells installed and operated during the last 20 years.  Based on these considerations, Directional Technologies installed one 300-foot long, 3-inch diameter polyvinyl chloride (PVC) horizontal well screen within a few feet of the centerline of the rectangular building.  The horizontal well screen was placed mostly in the depth range of 1.6 to 1.8 feet below the slab, or 2.6 to 2.8 feet below the building floor.  Directional Technologies was careful to maintain the client-required 12-inch clearance above a 6-inch diameter sewer line, and was able to respond to real-time directives from the building owner during the drilling operation to maintain varying preferred depths below different rooms of the building depending on footer and electrical conduit bank locations.

Directional Technologies completed the horizontal well screen installation in two days, and office workers in the building were able to work continuously without interruption throughout the remedial construction.

Horizontal well screen vaccum rates

Performance Test

Vacuum monitoring points were installed at distances ranging from 6 to 64 feet on either side of the horizontal well screen.  The zone of influence of the horizontal well screen was measured during a performance test with the horizontal well operating at varying pressures, increasing stepwise from about 10 to 40 inches of water.  The test revealed optimal flow between 1 and 1.5 standard cubic feet per minute (scfm) per foot of screen.  The horizontal well screen induced a vacuum in the compacted backfill that was measurable at monitoring points up to 63 feet away from the horizontal well, thereby creating a zone of influence essentially covering the entire subslab area of the building.  The moisture-laden areas beneath the slab exhibited a reduction in relative humidity from  above 95 percent before the horoizontal well began operating, to below 70 percent after the performance test.  Engineered slot distribution provided by Directional Technologies ensured that vacuum was evenly distributed in the subslab soils along the entire 300-foot long horizontal well screen.

Radius of Influence

Conclusion

Shallow horizontal extraction wells installed beneath commercial building slabs are becoming an important tool for environmental managers tasked with achieving regulatory site closure with solutions to multiple problems, including groundwater and soil contamination, soil and building slab moisture, and vapor intrusion concerns. Horizontal extraction wells provide efficient installation techniques that avoid disruption of ongoing business, ease the burden of installation, and coupled with engineered well screens enable operation at vacuum levels and flow rates that allow efficient long-term operation of the horizontal remediation/mitigation system.

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Directional Technologies is the nation’s expert horizontal remediation well drilling contractor.  We design and install horizontal remediation wells.  Directional Technologies’ experience in the oil field, environmental remediation and utility industries allows us to complete projects that were previously considered unfeasible.  Our company personnel have been successfully directional drilling horizontal wells since 1984! 

Contact us by email at drilling@directionaltech.com  or call 1-877-788-4HRW to discuss your possible horizontal remediation well project 

Horizontal Wells allow Rapid Clean up of R&D Facility Gasoline Release

Horizontal Soil Vapor Extraction and Horizontal Air Sparge Well Case Study-

Installation to remediated site closure

Background

Installing horizontal remediation wells to acheive rapid site closure

A Research and Development facility in central New Jersey released several thousand gallons of gasoline to the subsurface.  Environmental investigations revealed that approximately 80% of the phase separated plume existed below the building.  Uninterrupted operation and prevention of vapor intrusion in the facility were key factors that dictated an alternative approach to the remedial strategy.

Hudson Environmental Services, Inc. of Matawan, New Jersey completed the remedial investigation, assessed remedial alternatives and proposed a remedy.   Horizontal air sparge (AS) and horizontal soil vapor extraction (SVE) with vapor treatment utilizing catalytic oxidation was the recommended and selected remedy.

The Challenge Presented

Two technical approaches were available for the horizontal air sparge (AS) and horizontal soil vapor extraction (SVE)  system orientation: install a series of multiple vertical wells (a number would be required inside the building) with an interconnecting subsurface piping network, or install three horizontal wells, which would pass beneath the building.  Feasibility and financial analyses indicated that the horizontal well system would not disrupt business operations, be less expensive and more efficient than the traditional vertical well approach.  Directional Technologies, Inc. was engaged to install the horizontal wells.

Directional Technologies at Work: Our Solution

Pilot testing and subsurface characterization provided data enabling Directional Technologies to design two horizontal air sparge wells and one horizontal soil vapor extraction well.  The horizontal air sparge and horizontal soil vapor extraction wells were designed to operate at 250 cubic feet per minute (CFM).  The system design included a catalytic oxidizer to destroy hydrocarbon vapors extracted from the horizontal soil vapor extraction well.

The NJ Department of Environmental Protection (NJDEP) approved the remedial design following the first design submittal. Underground utilities, building footings and other subsurface structures were identified and surficially marked out prior to well installation.  Directional Technologies designed the horizontal well trajectories to avoid these buried structures.

Directional Technologies used a Ditch Witch Directional Boring System to directionally drill the horizontal wells and has used this drill rig to successfully drill bores up to 12 inches in diameter and 700 feet long; while compact in

size, it is extremely powerful.  The rig’s compact size allows it to be used in relatively confined areas and the rubber tracks exert minimal ground pressure,minimizing risk of damage to pavement and turf.  The power and two speed spindle rotation capability enabled the rig to successfully penetrate both hard and soft soil conditionsencountered at the site (fine sands, silts and clays).

Directional Technologies advanced each pilot hole to the specified depth and horizontal termination point using a spade bit.  Drill bit X-and-Y axis directional control and operational temperature was provided by a hand-held surface walk-over radio detection instrument.  The instrument receives continuous radio signals from a battery-powered instrumentation module contained in a length of drill pipe located directly behind the drill bit.  Regularly measuring drill bit temperature is important to ensure that drilling fluids are circulating through the drill bit, especially when drilling in rock.

Directional Technologies enlarged each pilot hole to a diameter of 6.5 inches using a spiral-cutting-configured back reamer drill bit designed to minimize formation displacement and compaction. Cement grout pumped through tremie pipes formed a seal in the annular space between the riser and formation.  Directional Technologies developed the wells with water to flush out drilling fluid that may have entered the formation during the horizontal drilling process.

Directional Technologies installed two identical horizontal air sparge wells configured as follows:  4 inch diameter, riser length: over 500 feet, screened interval: 260 feet, installed depth:  22 feet below ground surface, 7-9 feet into the water table. The single horizontal soil vapor extraction wellwas configured and installed as follows: 4 inch diameter, riser length: over 480 feet, screened interval: 240 feet, installed depth: 8 feet below ground surface (5-7 feet above the water table).

The horizontal wells were constructed of SDR-11, a high density polyethylene (HDPE) product; Directional Technologies validated the choice of this choice product via detailed computer modeling.  Modeling further dictated the need for multiple slot-zones in the horizontal SVE well screen due to the multiple design goals of uniform air sparging and extraction and a flow rate of 250 CFM to the catalytic thermal oxidizer.   

Results that Reward

The time required to achieve site remediation can be conservatively calculated from the quantity of oxygen delivered to the site by the remediation system.  Directional Technologies designed/installed each air sparge well to deliver approximately 2 pounds per minute of oxygen to the subsurface, or a total of 4 pounds per minute.  At this oxygen delivery rate Directional Technologies estimated that site cleanup would be accomplished in approximately one year.

The AS/SVE system operated from March 1999 to October 2000 and removed approximately 17,000 pounds of gasoline.  The separate phase gasoline plume under the building was completely eliminated.  This resulted in the NJDEP approving” no further action” for soils.

To discuss your future horizontal remediation well project, contact Directional Technologies, Inc.  Horizontal Directional Drilling Services Kathy Sequino 203-294-9200 or by email at ksequino@directionaltech.com

Horizontal Drilling for Electrical Resistance Heating

Aggressive removal of dense non-aqueous liquid (DNAPL) phase tetrachloroethylene (PCE) and trichloroethylene (TCE) under an active manufacturing

Welding the black steel casing for the horizontal ERH system and horizontal SVE

facility is the objective of an electrical resistance heating (ERH) system that was installed using horizontal drilling.  Placement of electrical resistance heating electrodes within horizontal carbon steel pipe overcame concerns about traditional, vertically installed electrodes at the site:

1. Drilling inside of the active facility would generate dust and cause vibration that would interfere with the precision machining and manufacturing work performed in the building,
2. The labyrinthine distribution of multiple milling machines of many different shapes and sizes would interfere with vertical drilling work to install the ERH electrodes under the building,
3. Interruption of the non-stop, 24-hour-a-day production schedule was unacceptable to the owners of the operation, who were not responsible for the plume beneath the building because it emanated from a neighboring former drycleaning facility, and
4. A grid of vertical ERH electrodes would severely limit placement options for a horizontal soil vapor extraction (SVE) system that was required in order to prevent vapors generated by the ERH system from entering the indoor air of the manufacturing facility.

Horizontal drilling was used to allow the 24-hour production schedule to continue and to avoid the labyrinthine of milling machines in this active facility.

The Horizontal Solution to ERH Electrode Placement

Electrical resistance heating electrodes are distributed in the subsurface to create a network of triangular electrode groupings in cross section.  The purpose of such a configuration is to optimize the distribution of heat across the target zone, from top to bottom.  One set of electrodes is placed at a shallow horizon within the target zone, and another set is placed at a deep horizon.  Shallow and deep electrodes are staggered, so that they don’t overlie each other.

Vertically the target zone reaches from 2 to 15 feet below ground surface (bgs), but horizontally it spans a 17,000 square foot area of the building.  Electrodes are placed at only two different elevations, but multiple electrodes are placed along a given horizontal traverse.  Installing electrodes within horizontal casings is therefore much more efficient than installing them in vertical casings.  The flexibility of shifting electrodes within a horizontal casing that extends 200 feet across the building is an additional benefit of using horizontal drilling to install the electrodes.  This flexibility will allow the electrical resistance heating to be optimized in the course of its operation, as some portions of the target zone remediate more quickly than others.

Hybrid ERH and horizontal SVE Wells

The shallow ERH pipes served double duty as horizontal soil vapor extraction (SVE) wells.  Alternating sections of the pipe were slotted for SVE, or solid for ERH.  This configuration avoided the logistical problem of threading SVE wells into the network of ERH electrodes.

Horizontal Electrode Pipe Installation

Heavy, rigid black steel casing with 6-inch diameter was used for installing the ERH system. Directional Technologies employed both blind and entry-exit installation methods for the horizontal ERH system.  Each black steel casing was welded onto the casing string as it advanced into the wellbore.  See the illustration at the top of this article.  The shallow wells were only 3 feet below the building slab, so the drilling method was adapted to minimize communication through cracks in the foundation.  A grout seal was emplaced around the pipe where it crossed below the building foundation in order to prevent short-circuiting of the horizontal SVE system.  Installation of the deep wells 14 feet bgs in weathered sandstone and gravel formation was challenging because of the weight and limited flexibility of the black steel casing.  In completing the ERH casing under the manufacturing facility, Directional Technologies Inc.  brought to bear its 20 years of experience directionally drilling in every form of soil, sediment or igneous and metamorphic rock.

Round-the-clock site operations using sensitive milling equipment continued unabated by the directional drilling work in yet another example of Directional Technologies’ tradition of partnering with consultants and site owners/operators to ensure successful and unobtrusive remedial system operation.

Contact Directional Technologies, Inc.
Horizontal Directional Drilling Services
Kathy Sequino
ksequino@directionaltech.com
203-294-9200