What Affects the Cost of Horizontal Directional Drilling?

Large HDPE pipe laid in an open trench during underground pipeline installation works.

One of the questions we get asked most often is: “What affects the cost of horizontal directional drilling?" Closely followed by: "What do you charge per metre?”

The short answer? It depends. And we promise we’re not just trying to avoid the question.

With Horizontal Directional Drilling (HDD), the drilling distance is only one part of the cost. Two bores of exactly the same length can need very different equipment, planning, setup and time depending on the site and what is being installed. That’s why a proper HDD quote looks at the full project, not just the metres.

Here are some of the main factors that can influence the final cost of horizontal directional drilling.

1. Bore length

Yes, distance matters.

A longer bore generally means more drilling time, more drilling fluid, more wear on equipment and potentially more complex bore planning. But length on its own doesn’t tell the full story. A short bore in difficult rock, for example, may be more demanding than a longer bore in favourable ground.

2. Pipe diameter

Pipe diameter has a major impact on the drilling process. Larger pipe normally means a larger final bore, which can require more reaming passes, larger tooling and more powerful equipment.

The bigger the product pipe, the more work is usually required to prepare the bore for pullback.

That’s why a 110 mm installation and a 450 mm installation can’t realistically be priced in the same way just because the bore length is similar.

3. Pipe material and specification

The type of product being installed also matters. HDPE, steel, conduit and other products all have different handling, preparation and installation requirements. Pipe wall thickness, SDR rating, bend radius and jointing requirements can also influence how the product is prepared and pulled into place. Where HDPE pipe welding forms part of the scope, that needs to be considered as part of the overall job rather than treated as a separate afterthought when looking at the cost of horizontal directional drilling.

4. Ground conditions

Ground conditions are one of the biggest variables in HDD. Soft soil, clay, sand, gravel, fill, rock and mixed ground can all behave very differently during drilling. Different conditions may require different tooling, drilling fluids, production rates and reaming strategies.

Unexpected ground can also affect progress once drilling starts. This is why any available geotechnical information is useful during the quoting stage. The more we know upfront, the better we can plan the correct equipment and approach.

5. Entry and exit conditions

The bore may be underground, but the setup happens above ground.

HDD needs suitable entry and exit areas for the rig, support equipment and the product pipe.

Limited access, steep levels, restricted working areas or awkward entry and exit positions can all add complexity. Sometimes the route itself looks simple, but getting the rig and support equipment into position may be the real challenge.

6. Site access

Site access can have a significant impact on mobilisation and setup. Questions we often need to consider include:

• Can the drilling rig reach the entry point?

• Is there enough space for support equipment?

• Can trucks move safely on and off site?

• Is the ground stable enough for the equipment?

• Is access restricted by buildings, fences, traffic or existing operations?

A project in an open field and a project inside a congested industrial site may be the same length on paper, but they are very different jobs in practice.

7. Existing underground services

Existing services can affect both the bore route and the level of planning required. Water lines, sewer pipes, electrical cables, fibre, gas and other buried infrastructure all need to be identified and considered.

The more congested the underground environment, the more carefully the bore path needs to be planned.Service drawings, wayleaves and accurate detection information help reduce risk and avoid unnecessary delays. A clear surface does not always mean a clear route underground.

8. Reaming requirements

The pilot bore is only the first step. Depending on the pipe diameter and ground conditions, the bore may need to be enlarged through one or more reaming passes before the product can be pulled through. More reaming means more drilling time, fluid, tooling and equipment usage.

This is another reason why pricing only on the final bore length can be misleading.

9. Drilling fluids and water availability

Drilling fluids play an important role in many HDD projects. They help stabilise the bore, carry cuttings out of the hole and support the drilling process. The amount and type of fluid required can vary depending on the ground conditions, bore size and drilling method. Water supply, fluid management and disposal also need to be considered as part of the project setup.

10. Pipe preparation and welding

If the product pipe needs to be welded or assembled before pullback, there needs to be enough space and time to prepare it. This is particularly important with HDPE installations. The pipe may need to be welded into long strings before being pulled into the bore. That means welding equipment, trained operators, handling space and quality control all form part of the job. Good preparation here can make the final pullback far smoother.

11. Crossings and site constraints

Roads, railways, rivers, culverts, retaining structures and other obstacles can all influence the bore design. Some crossings may require:

• deeper bore profiles

• longer setup areas

• additional approvals

• specialist planning

• more accurate locating and tracking

• increased safety controls

  
  

The crossing itself may only be one part of the project, but it can heavily influence the overall drilling approach.

12. Mobilisation

Mobilisation is an important cost, especially on smaller or remote projects. The drilling rig, tooling, support equipment and crew all need to get to site. A short bore close to the contractor’s base and a short bore hundreds of kilometres away are obviously not the same project commercially. This is also why small jobs don’t always translate neatly into a low rate per metre. There are fixed setup costs involved before the first metre is drilled.

13. Project timing

Programme requirements can also affect cost. Urgent mobilisation, restricted working hours, night work, shutdown periods or tight completion windows may all require different planning.

Sometimes the most efficient drilling method is not the cheapest setup on paper, but it may reduce the overall impact on the project programme. That broader project view matters.

14. Risk and uncertainty

Every HDD project carries some level of risk.

Unknown services, poor ground information, restricted access, uncertain geology or incomplete site information can all make planning more difficult. Where the unknowns are higher, more allowance may be needed for contingency, equipment selection and execution risk. This is one of the biggest reasons why providing accurate information upfront helps. The clearer the project scope, the more meaningful the quotation can be.

So why can’t HDD just be priced per metre?

Because the metre is only the final unit of distance.

Behind that metre are equipment, crew, tooling, planning, setup, drilling fluids, reaming, pipe preparation, access, ground conditions and risk. A simple rate per metre can be useful for very early budgeting, but it should never replace a proper project assessment. The cheapest rate per metre is not always the cheapest overall project. A realistic quotation should reflect what it will actually take to complete the installation safely and efficiently.

What information helps us quote more accurately?

The more useful information you can provide upfront, the easier it is to assess the project properly. Helpful information includes:

• bore length

• pipe diameter

• pipe material and specification

• site location

• proposed route

• entry and exit points

• ground or geotechnical information

• existing services

• wayleaves and approvals

• site access

• drawings

• required programme

• any known restrictions or hazards

Even if you don’t have everything yet, that’s okay. A conversation early in the planning stage can help identify what still needs to be confirmed.

A good quote starts with a good understanding of the job

At Kayeworx Drilling, we’d rather understand the project properly than give you a quick number that doesn’t reflect what the job actually involves.

We’re a hands-on business, and our approach is practical: understand the route, understand the pipe, understand the site and then work out the right drilling solution.

Sometimes the project is straightforward. Sometimes it needs a little more thought.

Either way, the better the information going in, the better the planning, and the fewer surprises once work starts.

If you’re planning an HDD project and need help working through the scope before requesting a quotation, speak to the Kayeworx team. We can help you identify the information needed to assess the project properly.