Trenchless becomes ever more attractive

In the UK, pipeline construction seems to be stuck in a rut, writes Ed Naylor. On the Continent, however, trenchless techniques tend to top the list of installation choices. And minimal disruption is just one of the reasons.

From the layman's perspective, pipeline construction does not seem to have advanced. The basic ingredients remain the same - a trench, a digger, labour, dust, dirt and traffic jams. But there is another way - trenchless technology.

There are various methods of trenchless installation including micro-tunnelling (installing new pipelines), directional drilling (common for small-diameter ducting) and pipe bursting (replacing existing pipelines).

Within the UK, the use of trenchless technology is far less widespread than on the Continent. Here, countries such as Germany place great emphasis on trenchless options, which are generally considered first. There are several reasons for this:
  • Environmental issues are higher up the agenda
  • There are more contractors with greater expertise and more equipment
  • Better records of existing services enable pre-existing pipelines and ducts to be avoided
But, despite these factors, there is still much progress to be made, and far more UK sites could benefit from the reduced surface disruption of trenchless technology.

Trenchless pipe installation often carries little, if any, price premium. Generally, the deeper the pipeline, the more likely it is that trenchless technology will offer a comparable or even cheaper alternative to open-cut pipe-laying.

There are situations where trenchless installation is the only sensible approach, such as where pipes need to be installed under waterways, railways and heavily trafficked areas or in ground conditions where it is simply too difficult for trenches to be economically constructed and worked.

Prospectively, several developments should encourage or even force contractors to adopt trenchless technology. The equipment has become cheaper and easier to use - trenchless technology is no longer the preserve of the specialist with expensive kit and a high degree of expertise.

And those undertaking drainage works face increased legislative pressures, which encourage greater environmental consideration. Legislation such as the New Road and Street Works Act 1991, the Traffic Management Act 2004 as well as section 74 charging and lane rental schemes aim to achieve less disruptive working on highways.

These, as well as other measures such as landfill and aggregate tax, should lead to an increasing reappraisal of the trenchless options.

So, the contractor may be receptive to trenchless technology. But, in addition, both engineer and client need to be willing to consider alternatives to conventional pipe laying. Their holistic view of the overall impact - financial and environmental - of proposed works often increases the attraction of trenchless pipelaying, with trenchless schemes simultaneously reducing aggregate use, timescales and surface disruption.

Historically, however, environmental impacts have been largely ignored because the costs of surface disruption are generally borne by the travelling public and local inhabitants rather than the client or the contractor.

A recent Anglian Water project in Grays, Essex, highlights the potential benefits of trenchless technology. The initial proposal was to upsize an existing pipeline by digging up an estate road, potentially causing commercial disruption to the businesses accessed by the road. Contractor Barhale proposed an alternative - installing 600mm diameter Naylor Denlok clay jacking pipes by micro-tunnelling.

Potentially affected businesses traded normally with minimal service disruption, and at negligible additional contractual cost with the added bonus of no adverse environmental impact caused by traffic hold-ups.

Similar benefits have been experienced at coastal resorts in Yorkshire where
construction programmes have been able to continue into the summer months without disruption to the tourist industry.

Trenchless technology is not a panacea. There are situations where the ground conditions are unsuitable, where there are multiple, poorly documented services or where the costs are prohibitive - trenchless installation of a pipeline on a
greenfield site at shallow depth is never likely to be economic. And the political pressures are not really there. Maybe they will be when that the red-top newspapers call for a public enquiry as open-cut pipelaying leads to Bank Holiday
motorway mayhem.

Edward Naylor is chief executive of Naylor Drainage.
T: 01226 794061

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