Directional Boring vs. Trenching-Which Is Right for Me?

A common question for people who are unfamiliar with underground regards to the differences between directional boring and trenching-and which method is right for their particular project.  For commercial project requests generally customers understand the difference and which method is more suitable for their needs based upon the project and path their projects takes. For “first time enterprise or residential customers, those who may not understand what the difference is (or that there even is a difference!), it isn’t quite as simple.

First, trenching is simply put the basic opening of ground from above in a path or path-like manner. Trenchers are best and most easily described as being similar to a large chainsaw, one with tines that open up the ground repetitively and, for the most part, easily, ground conditions notwithstanding. Trenchers can be the size of a large rider lawnmower or can be as large as a tractor, depending upon the complexity of the project and power needs. Most trenches, especially for residential sized projects, are typically anywhere from 6-12” in diameter and range in depths from 18”-60”. Trenching is most commonly used in open areas where ground disturbance is not of concern; trenching literally rips open the ground and, once filled with whatever conduits/pipes are needed, need to be back-filled will the material that was originally removed from the ground. It is important to note that trenching and excavating are 2 very different methods, both in machinery and complexity. OSHA defines an excavation as any man-made cut, cavity, trench, or depression in the earth’s surface formed by earth removal. A trench is defined as a narrow underground excavation that is deeper than it is wide, and no wider than 15 feet. Most likely a residential project would be for trenching as opposed to excavating but larger projects that require more Earth moving will need the power and ability of an excavator. Excavating is the most intrusive of all 3 methods discussed here.

Directional boring is done for many of the same purposes that trenching is; the biggest difference in the effectiveness of the 2 methods is that directional boring is much less invasive to the terrain. Directional bore machines, or “boring rigs”, simply bore down through the surface of the ground to open up a tunnel underneath in order to facilitate the placement of conduit for things as electrical service, sewers, or fiber optic cables. Directional boring rigs are typically much larger than trenchers but the effect they have on the surface-particularly in an area where aesthetics are important such as landscaped yards-are, much less invasive.

Which is right for your project? It all depends upon what you are looking to have done. Your description and project parameters – collectively make up what is referred to in our industry as a scope of work. Things such as work distance, path taken, conduit needed for placement-all of these make up the scope of work. But the biggest thing to think about when choosing whether directional boring or trenching should be the basis for the scope of work is where will the path of work to your contractor?

Typically, directional boring is more costly per linear foot than trenching is. However, there other things to factor besides the cost per foot for an underground construction company to effectively quote a project. The scope of work should dictate which method makes the most sense to you. If you are a residential customer and conduit needs to be placed under your driveway? If you are not prepared to cut open and buy a new driveway then directional boring is the answer. Are you a utilities contractor that needs to run power under streets? Unless you want to close these streets down, open them up, and give the local municipality a good reason to do so then I would suggest directional boring as your method.

If you are looking to get a quote for a project and the surface you re considering being trenched is asphalt or concrete (such as a parking lot, to run electrical power between light poles), your trenching contractor will need to “open cut” the surface before trenching the ground below. This involves the cutting and removal of all the now-ruined asphalt or concrete. Then your contractor will need to trench the area, place the conduit, back-fill the trenched areas, and, after all that is complete, resurface the area with new asphalt or concrete. It is a very time consuming process and, even if the contractor hired to do the work is not an hourly crew, all of this time has been built into the quote you received. Then we have the factor that is not always addressed-at least from what my customers have explained to me. There is the matter of all of the broken material or “spoil” that remains.

If you are considering a trench or excavation project, when obtaining a quote make sure that the quote includes not only the work itself but the extra such as removal of spoil and the transportation of the spoil to a landfill. Dependant upon the size of the job in question and the amount of spoil, this can easily break the budget for customers as this unforeseen cost can be 20% or higher of the original quote. There also may be environmental fees for depositing this spoil as some landfills do not want to take what basically amounts to unneeded or unusable garbage. Certainly things like the spoil mentioned here have an effect on the Earth with over-pollution, in the “Green Era”, being a common menace. With directional boring there is very little spoil and no need for a dump truck to be loaded full of concrete to be taken somewhere to rot for the next 50-100 years.

If you are looking for a quote for what you consider to be a trenching or excavating project, make sure all of the following are built into the Final Quote that you receive from your contractor:

- Open cutting of surface material
- Placement of conduit/pipe needed
- Restoration of the area to its original appearance
- Removal of spoil
- Any environmental fees associated with depositing the spoil at a landfill

Only then is one really comparing all of the methods properly. Trenching itself on a per foot basis is cheaper than directional boring and is useful at times, particularly in large, open “field” like areas. However, when factoring in all of the other costs listed above, there is no doubt that directional boring more than ever has its place in the underground construction world. More and more often, customers both residential and commercial, are choosing to “go green” and choose directional boring.

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