Horizontal Directional Drilling vs Open Trenching: Which is Right for Your Project?

Horizontal Directional Drilling

When you’re planning an underground pipeline or service installation, one of the first questions is often whether to use traditional open trenching or a trenchless method such as Horizontal Directional Drilling (HDD).

The answer isn’t always obvious.

Both methods have their place, and the right choice depends on the site, the product being installed, existing infrastructure, access, ground conditions, environmental considerations, project timing and overall risk.

In some cases, open trenching is still the simplest and most practical option. In others, HDD can reduce disruption, avoid major surface excavation and make difficult crossings far more manageable.

The important part is choosing the method that suits the project, not forcing the project to suit the method.

What is open trenching?

Open trenching is the traditional way of installing underground pipes or services.

A trench is excavated along the route, the pipe or service is installed, and the area is then backfilled and reinstated.

It’s a tried-and-tested method and can work very well where there is plenty of space, easy access and limited surface infrastructure. Open trenching may make sense where:

• The route is relatively clear

• There is enough working space

• Excavation won’t cause major disruption

• The installation is fairly shallow

• Reinstatement is straightforward

• The ground conditions suit conventional excavation

Sometimes, the simplest solution really is the best one.

What is Horizontal Directional Drilling?

Horizontal Directional Drilling is a trenchless method used to install pipes, conduits and underground services with far less surface excavation. Instead of opening a trench along the full route, HDD generally works from an entry point to an exit point.

A pilot bore is drilled underground along a planned path. The bore is then enlarged, where required, before the product pipe is pulled back through.

This makes HDD particularly useful where the route needs to pass beneath existing infrastructure or where opening up the surface would create unnecessary disruption.

Typical applications include crossings beneath:

• roads

• railway lines

• rivers and drainage channels

• built-up areas

• environmentally sensitive areas

• existing infrastructure

• operational sites where open excavation would be difficult.

  
  

So, which method is better?

There isn't a one-size-fits-all answer.

HDD isn't automatically the better option simply because it's trenchless. And open trenching isn't automatically cheaper just because it looks more straightforward.

The better option is the one that makes the most sense for the specific project.

Here are some of the things we look at when helping clients assess the best approach.

1. Surface disruption

This is one of the biggest differences between the two methods. Open trenching means excavating along the route, which can affect roads, paving, landscaping, traffic flow, site access and day-to-day operations. HDD significantly reduces the need for continuous excavation.

Where you're crossing a busy road, working on an operational site or trying to avoid major disruption, that can be a big advantage.

That said, HDD still needs proper working space for the rig, support equipment, pipe preparation and entry and exit areas.

Trenchless doesn't mean space-free or impact-free.

2. Reinstatement

The job doesn't end once the pipe is in the ground. With open trenching, the disturbed area must usually be reinstated afterwards. That may include:

• road repairs

• paving

• landscaping

• concrete work

• rehabilitation of disturbed ground.

  
  

These costs and time requirements can add up quickly.

Because HDD reduces surface excavation, it can also reduce the amount of reinstatement required — particularly where the surface is expensive, sensitive or difficult to repair.

3. Roads and traffic

Road crossings are one of the most common reasons clients look at HDD. Open trenching across an active road may mean lane closures, traffic accommodation, excavation, backfilling and road reinstatement. On a busy road, that can become a major logistical exercise.

HDD allows services to be installed beneath the road while keeping surface disruption to a minimum. You still need the right approvals, planning and service information, but the physical crossing itself can be far less intrusive.

4. Existing underground services

What you can't see underground matters just as much as what you can see on the surface. Water lines, electrical cables, fibre networks, sewer lines and other buried services all need to be considered.

With open trenching, these services may need to be exposed and worked around. With HDD, the bore path needs to be planned carefully to maintain suitable clearance from known services. This is why wayleaves, service drawings and proper service detection are so important.

A clear-looking site doesn't necessarily mean a clear underground route.

5. Ground conditions

Ground conditions can change the entire approach to a project. Soft soil, rock, groundwater, fill material and mixed ground can all affect the drilling or excavation method, equipment choice, production rates and project risk.

HDD can work very effectively in many different ground conditions, but the setup and drilling approach may need to change depending on what is expected below ground.

The same applies to open trenching. Where possible, good geotechnical information helps everyone plan better and reduces surprises once work starts.

6. Installation depth

Depth is another important consideration.

A shallow installation across open ground may be simple enough to handle with conventional excavation. As trenches become deeper, however, the work can become more complex. You may need additional shoring, battering, safety controls and a larger working area. In some cases, HDD can offer a practical alternative by allowing the bore to pass beneath an obstacle without opening a deep trench along the full route.

7. Site access and working space

This is one of those practical details that can easily be overlooked during early planning.

HDD requires enough space for the drilling rig and support equipment. The pipe may also need to be welded or assembled before pullback, which means you need sufficient space along the alignment or within the site.

Open trenching also needs access for excavators, trucks, spoil handling and reinstatement equipment. A project may look perfect for HDD on paper, but limited rig access or pipe preparation space can change that.

That's why proper site information, and often a site visit, is so useful before finalising the method.

8. Environmental and community impact

Where projects run through developed communities or environmentally sensitive areas, reducing surface disturbance can make a meaningful difference. Less excavation can mean:

• less vegetation removal

• less spoil handling

• fewer access disruptions

• fewer road closures

• less disturbance to surrounding activities.

  
  

Of course, every project still needs to meet its environmental, permitting and site-specific requirements. HDD reduces surface impact, but good planning remains essential.

9. Project timing

People often assume HDD is automatically faster. Sometimes it is. Sometimes it isn't. Timing depends on the complexity of the bore, ground conditions, mobilisation, approvals, site preparation and pipe installation requirements.

On a simple, open site, trenching can be very efficient too. So the better question isn't:

Which method is faster? It's: Which method gives us the most efficient overall project once excavation, installation, reinstatement, access and disruption are all taken into account?

10. Cost

Cost is usually one of the first questions,understandably. But comparing HDD and open trenching purely on a rate-per-metre basis can give a misleading picture.

With open trenching, the full cost may include excavation, spoil handling, shoring, backfilling, compaction, traffic management and reinstatement. With HDD, costs may include mobilisation, specialist drilling equipment, drilling fluids, reaming, pipe preparation and the drilling operation itself.

The cheapest metre isn't always the cheapest project. The better comparison is the total project cost, including the risks, disruption and work that needs to happen before and after the installation.

When does HDD make sense?

HDD is often worth considering where:

• the route crosses roads, railways or waterways

• surface disruption needs to be kept to a minimum

• access must remain open during construction

• reinstatement would be costly or difficult

• open excavation would interrupt existing operations

• environmental disturbance needs to be reduced

• existing infrastructure makes trenching difficult

• the required bore route is technically suitable for HDD.

When might open trenching still be the better option?

Open trenching may still be the better choice where:

• the route is open and easily accessible

• the installation is shallow

• surface disruption is limited

• there are few underground obstacles

• reinstatement is straightforward

• excavation conditions are favourable

• the project doesn't justify a specialist trenchless setup.

  
  

And that's okay. At Kayeworx, we're not interested in recommending HDD simply because that's the service we provide. The method needs to make sense for the job.

Choose the method around the project

The decision between Horizontal Directional Drilling and open trenching should come back to one thing: what is the most practical, safe and efficient way to complete the installation? Distance is only one part of that decision.

Pipe diameter, pipe material, route, entry and exit points, ground conditions, existing services, site access, wayleaves and project timing can all influence the answer. The more information we have upfront, the better we can assess the project and identify potential constraints before they become expensive problems on site.

We're a hands-on drilling business, and we prefer to have the practical conversation early: what are you trying to install, what does the site look like, and what could get in the way?

Sometimes HDD is exactly the right solution. Sometimes it isn't. The important thing is getting the method right before the work starts.

If you're planning an underground pipe or service installation and aren't sure whether HDD is suitable, speak to the Kayeworx team. We can look at the route, pipe specification and site conditions and help you work through the best way forward.

Updated: August 20, 2026.