The advantages offered by directional drilling can be just as beneficial for water and sewer construction as they are for communications, electrical power and natural gas projects.

While HDD does, indeed, have much to offer builders of segments of the underground public works infrastructure, demand for drilling services for water and sewer projects has lagged far behind that for the “dry” utilities.

The amount of water pipe installed by HDD increases each year, but even though some directional drilling contractors have been making on-grade installations for several years, the trenchless procedure has not made a major impact in the sanitary sewer market.

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There are two primary reasons why:

* The majority of those who operate and plan the construction of sanitary sewer systems are not aware that HDD is suitable for many of their projects; and * Many sewer system professionals who are aware of directional drilling do not believe HDD machines are capable of installing pipe at the critical grades essential for gravity-flow sewer systems; therefore they do not consider HDD a viable option.

Both viewpoints are based on either a lack of understanding or outdated information, as the technology to make on-grade bores is available now.

Directional drilling equipment today is capable of handling pipe in sizes that make up much of our sanitary sewer infrastructure. Similarly, guidance electronics designed to facilitate grade control – when properly used – help drillers achieve consistent results that make HDD on-grade installations cost effective for project owners and profitable for contractors.

These facts remain unknown to public works professionals largely because the HDD industry has not promoted the proven technology directional drilling offers the civil engineers, public works engineers and managers who plan sanitary sewer projects.

On jobs appropriate for HDD, significant savings in restoration costs can be realised.

BTB Australia has recently worked on a number of projects involving sewer installations, including pressure sewer installations, gravity sewers and sewer to grade.

At Mernda, BTB has installed 180 m of 150 mm sewer pipe on a grade of 1:158 in solid bluestone rock formation, and is continuing with a number of other similar bores on the same project for MFJ Constructions. The installations are generally through existing properties with limited access, and the time and environmental benefits were a determining factor given the rock conditions.

BTB has also completed two large diameter bores on the Mernda project for Tenix and Yarra Valley Water, also in extreme rock conditions. A third bore crossing under the Plenty Gorge and installation of a 400 mm pressure sewer pipeline are almost complete.

BTB is currently completing work in Flinders, installing a complete pressure sewer system as the primary contractor for Utility Services. Over 13 km of pressure pipeline, fittings and valves have been installed.

These pressure sewer systems are becoming more popular with the utility companies and they offer a great deal of cost and environmental savings as compared to traditional open cut sewer constructions.