Trenching verses plowing and what is microtrenching? Christine Smith, product marketing specialist for utility and productivity tools for Vermeer Corporation outlines some best practices for underground utilities
By Christine Smith
Whether an underground utilities crew is installing fibre optic, conduit, cable, electrical, gas or water lines, choosing the right installation method is imperative to helping maximize productivity.
While estimating a project, contractors should ask themselves, “what’s the right installation method for this project?”
HDD or open cut?
According to Ed Savage, product manager at Vermeer Corporation, there has been a significant shift toward horizontal directional drilling in the underground utilities industry.
However, there are still many instances where open-cut methods including trenching, plowing and microtrenching, are a more cost-effective and efficient method.
“For many contractors, the installation method they utilize is driven by the equipment in their fleet,” Savage explained.
“While specializing is good for contractors, adding additional installation services can help grow their business.”
Savage also explained that while many underground utilities contractors consider the various open-cut methods to be very similar, several factors should be considered before choosing one way over another.
Those considerations include:
- Ground/soil conditions.
- Installation depth.
- Size and type of utility.
- Existing infrastructure.
Plowing pros and cons
“For direct bury or small poly conduit in soft/loamy soil conditions, a vibratory plow is typically the fastest installation up to around (106.6 cm) in depth,” Savage explained.
“The product is usually installed in a single pass, and there is a lot less restoration work required afterward.”
However, there are limits to just how much a vibratory plow can do. Savage explained there are some plows that can go deeper than 106.6 cm, up to 121.9 cm, but the soil conditions have to be ideal and the size of the tractor required to pull that deep may make it a less-efficient option at that point. Plows also have a more limited trench width than trenchers.
Pros and cons of trenching
Trenchers come in a broader range of sizes, adapt better to various applications, are able to dig deeper and handle a wider range of soil types than vibratory plows.
“While trenching will work in a greater range of environments and project types, the overall process takes longer than plowing,” Savage said.
“Trenching jobs require more restoration work after the product is in the ground and contractors may need to bring in additional equipment to complete that portion of the job.”
Savage added that trenching is an excellent option for utilities that need to be set on-grade and have a large diameter.
What about micro or nano trenching?
These methods work well on fibre optic or small conduit jobs, as they are often more cost-effective and can take less time than other installation methods.
A micro or nano trencher is used to open a narrow and shallow trench in an asphalt roadway, usually in the seam between the asphalt road and concrete curb or apron.
“In many cities, the underground right-of-way is becoming crowded,” Savage said.
“Micro or nano trenching allows contractors to avoid other utilities, and future repairs to damaged lines can be easier to access.”
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Some jobs utilize only one installation method, but ground conditions can fluctuate, and installation depths can vary. For projects like these, Savage said contractors shouldn’t limit themselves to a single installation method.
“The right method is the one, or sometimes two methods, that allows a crew to maximize productivity while still maintaining the highest safety standards,” he added. “That may mean a crew uses a vibratory plow for the majority of a project, but uses a trencher in more challenging soil types or a horizontal directional drill to go under roadways.”
When choosing between trenching, plowing, micro or nano trenching or drilling, understanding the underground utilities installation options available can help lead to better decisions and a more successfully completed job.