- Bill Poupis

Limited access, also referred to in the drilling industry as restricted access, is characterized by a variety of spatial, ventilation, terrain, or operational limitations which, when encountered in the field, require specific drill rig adaptations. While we may be tempted to think of limited access just in terms of urban settings, drillers frequently find these challenges on rural job sites and even in marine environments.  

Conditions which require specialty drill rigs include:


    • A drill site that cannot accommodate a full-size rig with support vehicles and crew. This is often the case in crowded urban settings as we discussed in our previous blog on bioswale installation under New York City’s Green Infrastructure Plan.

    • A low overhead clearance requires a drill rig with a short tower. Typically, a clearance under 15 feet warrants consideration of limited access options.

    • Air quality is a major concern when drilling operations move indoors. Proper exhaust ventilation of diesel or propane equipment or alternative engine type is required to protect the crew, other on-site personnel, or even the workforce of an active facility.

    • Atypical surfaces may warrant specialty equipment. Drilling over the water, on uneven surfaces, or off-road are common situations that are easily managed with limited access equipment.

Historically, limited access drilling has been associated with environmental drilling applications.  But as we’ve seen at ADT, there is a significant demand for limited access operations in geotechnical drilling, especially in a hot real estate market. Geotechnical data is required for building design and permitting. Limited access drilling operations can retrieve the necessary geotechnical data prior to tear down of an existing building which shortens the project life cycle of tear down, permitting, design, construction and property sale.


Limited Access Drilling Sites Not Restricted to Sonic

Limited access drill rigs are not technology-specific. There’s a wide range of options for direct push, auger, rotary, and sonic drilling methods. With so many drilling equipment options, how do you choose the right rig? It all comes down to the specific site restraints and your project goals.

  • Low clearance rigs are available in every drilling technology and often include other limited access features such as track/skid mounted, “assemble on site” and electric motors, just to name a few. Track mounted sonic rigs under 14 feet, hollow stem auger rigs under 12.5 feet and electric rigs under 10 feet are each common options for low clearance drilling rigs. There is no one ‘go-to’ rig type for limited access.
  • The ultimate indoor drilling option is like a real-life Lego set; the FORDIA/EXPLO 220/mud rig is an aluminum rig with clearance under 8 feet designed for restricted entry and space constraints. The crew disassembles the rig, moves the pieces to the desired location, then reassembles at the drilling site.  
  • Modifying a rig platform to accommodate alternative drilling technologies is a common solution for limited access challenges. The Geoprobe 420M direct push platform has been modified for mud rotary and air hammer to perform a variety of environmental well installation and sampling tasks.
  • Bring in the barge for environmental and geotechnical drilling over the water. Barges are available in a wide range of sizes and capacities so rigs and crews of nearly any size can be mobilized.
  • When getting into a building isn’t an option, go around. Angle drilling is available via sonic, auger, and direct push rigs, both truck and track mounted.


Safety Knows No Bounds

Limited access drilling brings a unique set of safety concerns. First and foremost is the well-being of the operator and crew. Ensuring adequate space for the crew to move around safely as well as maneuvering the rig during operations is paramount to maintaining our safety standards. Restricted track mounted rigs are operated with a radio or tethered remote allowing the operator to stand clear of the rig while setting up on the drill location.

There are two primary concerns with indoor drilling - ventilation and temperature. Engineering controls on the rig are necessary to ensure proper ventilation of diesel or propane rigs in a confined space. Ambient temperature does impact the rig choice but does require additional health and safety precautions and work plan modifications are to protect the crews from extreme heat or cold.

The same worksite hazards of standard drilling operations are also a concern with limited access drilling. These risk factors include exposure to dust, noise, moving equipment, and slip/trip/fall. Proper health and safety training along with a properly implemented work plan (JSA) help reduce the risk of injury.


Managing Expectations

There is no intrinsic reason for limited access drilling to go awry.  There are, however, additional considerations in planning and executing the work.  So what can you expect with limited access drilling?  


    • When specialty equipment or additional engineering controls are necessary, limited access drilling operations simply take longer than performing the same task in unrestricted conditions.  When space is limited, the crew is working with short lengths of casing and drill rods.  Plan for additional time for mobilization, demobilization, and drilling operations.  

    • Specialty equipment and skilled operators carry a premium price.  As mentioned above, the slower pace of operations means additional time on site.  All of this adds to higher cost of completion.

    • Limited access drilling is a niche skill. Investing your time and effort to find an experience drilling contractor with an impeccable safety record and a diverse fleet of limited access drilling equipment will definitely pay off in the long run. Be sure to ask contractors about their safety program, project references, and contingency plans for overcoming unexpected challenges during operations such as mechanical problems, geological issues, and physical limitations of the job site.



Bill Poupis is the General Manager at Aquifer Drilling & Testing, Inc. (ADT), a subsidiary of Cascade Environmental. Bill holds a BS degree in Geology and has over 37 years of drilling experience. Bill joined the Cascade team in 2015 through the acquisition of Aquifer Drilling & Testing, Inc. where he spent 18 years providing drilling and related services for environmental, geotechnical and geothermal applications. ADT provides a full range of environmental and geotechnical drilling services with an extensive fleet of sonic and conventional drilling rigs and specialty equipment. They have been proud to serve the greater New York City area since 1989.

Related Resources