FREQUENTLY ASKED QUESTIONS
FREQUENTLY ASKED QUESTIONS
We’ve assembled the most commonly asked questions about trenchless construction, and the trenchless services we offer.
For project-specific inquiries of a more technical nature, we encourage you to contact us directly. Every trenchless project is different and there are many factors to be considered. We will ensure you get the right answers – and the most appropriate trenchless solution – for your construction challenge.
Trenchless construction is a low disturbance excavation method that does not involve continual surface excavation. It is primarily used for the installation, rehabilitation or replacement of pipelines, utilities and other underground infrastructure. The most common trenchless methods are: horizontal directional drilling, augering, boring, tunneling and hydrovac.
Trenchless is primarily used when product lines must be installed beneath (or in close proximity to) an important or environmentally sensitive crossing points. Roads, railways, pathways, infrastructure and businesses can remain open during installation. New lines can be placed under live lines. And product lines can be safely installed under important water crossings and other natural habitats.
There is a trenchless solution for all geologies and an impressive range of product diameters and lengths – making it a practical solution in many situations where excavation is prohibitive.
Several factors will determine the most appropriate solution to your trenchless needs. This includes, but is not limited to:
- Installation length
- Soil Conditions/Formation
- Precision of Alignment and Grade)
- Product Material (eg. steel vs polymer)
Horizontal Directional Drilling lends itself to longer installations between 150 m to 3,000 m (492 ft to 9843 ft) and under 1.5 m (60 in) in diameter. For shorter installations and those involving large diameter, there are a variety of tunneling methods to choose from.
The Crossing Company’s Trenchless Solutions Calculator can help you determine which method(s) are best suited to you project. Simply enter the required length and diameter to view your options.
* Due to the complexity of trenchless construction, contact The Crossing Group to discuss your project in detail so we can provide you with the right solution to your challenge.
HDD is a method for installing pipes, conduits and cables using a surface-based drilling rig. Material is removed from the hole both hydraulically and mechanically using drill pipe and a bottom hole assembly (BHA). The bottom hole assembly is made up of a drill bit, mud motor and steering tool. Using either a surface coil or a walk over steering system, a pilot hole is drilled along a pre-determined path. Depending on the final diameter, a reamer (also known as a hole opener) is used to increase the diameter of the hole to accommodate the produce line.
Our HDD fleet can drill diameters ranging from 51 mm (2 in) to 1,524 mm (60 in).
Maximum lengths and hole diameters are determined by project specific geotechnical conditions however effective outside range for heavy rig horizontal directional drilling is 3,000 m (9,843 ft).
Light rigs are typically used for crossings between 50 m and 1,000 m (164 ft – 3,281 ft).
Our heavy rigs range from 7 - 20 standard oil field loads, depending on the size of the rig and the project-specific equipment requirements. Light rigs range from 3 to 7.
The minimum pad size required for a heavy rig is a 40 m x 60 m (131 ft x 197 ft) level pad with the rig located near the center of the pad. This pad size is actual work space and does not include the spoils.
The typical light rig spread operates on a footprint of 10 m wide by 30 m long (33 ft x 98 ft). This includes the drilling rig, support truck, drill stem trailer, and water truck.
Production rates vary based on the geological formation and size of the product line.
For a light rig, it is reasonable to setup, drill 400m in one 12-hour shift. Heavy rigs can drill 140 m in a 24-hour shift.
HDD is regularly employed in the installation of fiber optic cable, water and sewage mains, and electrical lines. It is also used to install all types of oil and gas pipelines.
The Crossing Group’s success rate across all HDD divisions is 98.75%
An "Intersect" is a technique in which two rigs, positioned at each end of a crossing, drill towards each other. One rig drills into, or intersects, the pilot hole created by the opposite rig. After the intersect, one rig withdraws from the pilot hole, while the drill string from the opposite rig chases it to the other end of the hole. Reaming operations can then be conducted with both rigs working in tandem, or the ream can be conducted in a conventional fashion using one rig only. The product line is pulled in using one rig.
Yes, all heavy rigs work 24 hours a day, seven days a week. There are 5 workers per shift, with two 12-hour shifts per day.
Light rigs typically operate 12 hours a day, seven days a week.
The steering mechanism varies between heavy and light rigs.
For heavy rigs, we use Tensor Steering Tools and Vector Magnetic Steering Tools positioned behind the drill bit in conjunction with Direct Current and Alternating Current electromagnetic coils on surface. The Tensor Tool has a stated accuracy of 0.1° Inclination and 0.25° Azimuth. The Vector Steering Tool has a stated accuracy of 0.1° Inclination and 0.4° Azimuth. The stated accuracy of the electromagnetic coils is 2% of the coil to bit vertical distance.
For light rigs, we have two different types of steering systems: "walkover" and "wire line".
Each drilling fluid program is project specific and is designed by a mud engineer. Most systems consist of a bentonite base and have a variety of polymers and additives added to the base system depending on the geotechnical conditions and the desired outcomes.
With adequate access for large trucks, the rig can be set up and ready to drill in under an hour.
To ensure the safety and integrity of our installation, we require the following before proceeding with any horizontal directional drill:
- Stamped trenchless design blueprints
- Geotechnical investigation findings
- RFP (if applicable)
HDD can be used to safely install pipe or utility lines with minimal disturbance in a number of situations, including but not limited to:
- Under environmentally sensitive areas (such as rivers, lakes, bays, wildlife corridors)
- Beneath busy roads, freeways, intersections, parks and golf courses
- Across existing utility or pipeline corridors; into plants and processing facilities
- Into marine environments (eg. desalination plants)
- Into residential communities
Yes. The Crossing Company can recommend the right engineered sound attenuation solution to meet your requirements, and have worked with suppliers across North America to meet the most stringent client demands.
The Tunneling Company offers numerous trenchless methods for installing casing horizontally underground. The ideal method depends on ground conditions, casing size, and crossing length. Our key services include the following:
- Horizontal Auger Boring
- Pneumatic Pipe Ramming
- Guided Boring
- Down The Hole Hammer
- Slip Boring
- Surface Casing
- Tunnel Boring/ Pipe Jacking
- Horizontal Directional Boring
The Tunneling Company has equipment and techniques to install casing/pipe from 25 mm to 3.6 m (1 in to 144 in).
Typically, we can complete a crossing under an active railway or major highway without any traffic disturbance. Because our techniques never leave a void in the ground there is no safety risk to motorist, railcars, or our crew. Our techniques are only displacing up to 51 mm (2 in) of material around the leading edge of the casing, so there is little risk of settlement or heaving.
In theory, we can complete crossings as long as the project requires, but are limited depending on ground conditions, casing size, and accuracy required. Typically, we install accurate line and grade crossings to about 150 m (492 ft). If the project requires greater lengths, we can design a plan that accomplishes your requirements.
We have equipment and techniques that allow us to ‘bore’ through virtually all ground conditions: from sand, clay, cobbles, to solid rock. The ground conditions play a large factor in determining which trenchless equipment we recommend for any given project.
In most cases, a high water table can be dealt with using various water management techniques and equipment.
Using a Guided Boring Machine, we are able complete a crossing up to 150 m (492 ft) within 25 mm (0.98 in) of accuracy at a specific % grade.
Typically, we can complete a crossing under an active railway or major highway without any traffic disturbance. Our techniques never leave a void in the ground, ensuring there is no safety risk to motorist, railcars, or our crew. Since we are only displacing up to 51 mm (2 in) of material around the leading edge of the casing, there is also minimal risk of road heaving or cracking of asphalt.
This depends on a number of factors, including (but not limited to): ground conditions, casing size, crossing length, weather, working conditions, line and grade requirements and any unforeseen obstructions encountered. Typically, we can install anywhere between 12 m to 18 m (39 ft to 59 ft) per day.
Most trenchless installations require a minimum jacking pit of 11 m x 3 m (36 ft to 10 ft), plus room for excavators and equipment lay down. If space permits, a longer set up site will allow us to install longer sections of pipe, which means less welding and a quicker completion of your project.
The cost of a project is dependent on the crossing length, casing diameter, ground conditions, site location and complexity of the project. Typically, a trenchless installation is not the most economical solution on a pure cost basis. However, the true value of trenchless is in its ability to reduce the impact of construction on the public (eg. minimizing traffic disruption), and the environment. When it comes to project design and outcomes – a trenchless solution is often the only solution.