What Is HDD?
The first horizontal directional drilling crossing in history was carried out in 1972 under the Pajaro River near Watsonville, California, USA. This 180-metre crossing, built to carry high-pressure gas, was completed by Titan Contractors (founded 1965) under the leadership of Martin Cherrington. That project was also the birth of the "horizontal directional drilling system".
HDD is a system that can drill in three dimensions underground. The drill bit can be steered up, down, left and right at any moment to create the desired underground profile. The classic procedure is to enter at an angle from the entry point, level out to 0° (horizontal) once the required depth is reached, and then come back up to the surface. If there is an obstacle on the planned underground route (existing utilities, foundations, etc.), the profile can be changed to pass under, over or beside it.
Once the pilot hole is complete and the drill head reaches the surface, this tool is removed and replaced by a larger-diameter back reamer fitted with cutting teeth to enlarge the pilot hole; the rig then pulls it back to the entry point, rotating along the axis of the pilot hole.
After reaming is complete, the horizontal directional drilling operation moves to its final and most critical stage: pipe or cable pullback. The pipeline connected behind the reamer is pulled from the exit point to the entry point without friction, thanks to the lubrication provided by bentonite mud. As pipe diameter and ground resistance increase, the pull force is calculated accordingly; this is why the pullback capacity of HDD rigs is one of the most important technical criteria set at the planning stage.
Since the first application in 1972, horizontal directional drilling technology has developed enormously. Systems that could once work only over limited depth and distance have become advanced rigs that complete crossings of hundreds of metres in a single pass, equipped with GPS and electromagnetic sonde technology. Thanks to this development, HDD is today one of the standard construction methods for infrastructure projects worldwide.
In Türkiye, too, horizontal directional drilling has been adopted rapidly, especially with the expansion of natural gas distribution networks. In city centres where the historic fabric must be protected, under busy streets and boulevards, and at river and strait crossings, HDD offers an indispensable solution. Most potable water, wastewater, power, fibre-optic and natural gas lines are now installed directly by HDD instead of open cut.
A successful HDD project depends on the geotechnical survey, route planning and the right choice of equipment. Different drilling parameters apply in sandy, clayey, gravelly and soft-rock formations; where the water table is high, ground stability is maintained by balancing the bentonite mud. Managing all of these technical details correctly guarantees that the horizontal directional drilling operation is completed safely and without problems.
At DELTEK we combine this technology, whose foundations were laid in 1972, with today's most advanced equipment and engineering know-how, and apply it across Türkiye with our Istanbul- and Izmir-based crews. With more than 20 years of experience we have successfully completed hundreds of HDD projects for the public and private sectors. Contact our team for a technical assessment and an HDD quotation for your project.
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