My first foray in to the world of HDD was 10 years ago, shortly after I began my current job as an instructor. We had instructors who taught HDD already, but our coordinator decided that it would be a good idea for me to shadow their class in case we needed to run an HDD class and they were not available. “Drilling is drilling, right?” he said.
So, I worked with our HDD instructors for a couple of classes and learned the process in case one of them got sick. I even got proficient with two different types of locaters but, at the end of the second class, went back to developing the vertical drilling curriculum.
One of the instructors was only part time and at the end of our training season went back to his contractor. What I did not count on was the other instructor getting into a fight with our coordinator and being let go. So, here we are entering the summer with me as the only one who has ever run an HDD drill. No big deal, right? We had never needed to run HDD classes over the summer … yet.
It just so happened that, at about the same time, a contractor installing gas lines in Chicago had some HDPE pipe fail a check by city inspectors. UV rays had gotten to the pipe and weakened it, and the contractor could not definitively say where all the suspect pipe had been used. The city’s response was, “replace it all” — every foot in the city. All the sudden we have a huge need for HDD operators, and we could not pull our part time instructor because his contractor picked up much of that season’s work. Talk about a baptism of fire. I was all HDD, all the time for the next six weeks.
Horizontal directional drilling, like any type of drilling, has inherent safety risks that must be mitigated. First, consider the drilling of a pilot bore. Entrance and exit pits are dug to allow for collection and/or reclamation of drilling mud, depending on the length and diameter of the planned bore. A pilot bore is drilled after the pathway — both vertical and horizontal — is planned. This plan must take into account the stiffness of the drill rods, the product to be installed, locations of all utilities and structures in the planned bore path, and the drill rig’s length-of-bore-at-diameter capabilities.
Pilot bore risks include, but are not limited to:
Utilities: These should be located and fully exposed to determine vertical and horizontal location. The planned bore path needs to maintain clearance of the product being pulled back at its tolerable bend moment.
Electric strike: All drills must be grounded and have a working strike alert system. Operators should wear dielectric boots and gloves that guard against the dangers of unexpected voltage surges.
Gas or liquid line strike: In the event of a gas or liquid line strike, the operator should immediately shut off the engine and evacuate the area. Contact the utility company. Do not return to the jobsite until the utility company has given permission to do so.
Sewer cross bore: Cross bores can occur between the intersection of a gas line or electric line and a sewer line. These can be potentially very dangerous. Homeowners or plumbers can inadvertently — while clearing a blockage of a sewer line — sever gas or electric lines installed by HDD. This can cause injury or even death.
Drill rods: Directional drillers do something quite strange to vertical drillers: They push the rods without turning. This creates the possibility in hard material that rods could bend or break with the driller sitting just a couple inches away. Drillers face ever-present spinning rod hazards during operations.
After the pilot bore, drillers attach a reamer to the drill string and drill back to the rig. This process can be a single-pass or multiple-pass operation. If it is a single-pass operation, the product follows the reamer directly. In a multi-pass operation, the drill pulls another string of drill rods behind the reamer. A larger reamer attaches to that string, and drills back until the desired diameter is reached.
Reaming and product installation risks include, but are not limited to:
Bit changes: Drilling implement changes happen far from the drill, often out of site of the operator running the drill. This requires lockout of the drill controls during tooling change. This excerpt from a NIOSH FACE Report mid-spring 2005 should make every crew member stop and think:
A construction worker died while installing pipe with a horizontal directional drilling (HDD) machine. The victim had attached the swivel between the pipe and back reamer. The victim reportedly replied affirmatively to the rig operator who then energized the drill pipe. After a few revolutions, the rig operator radioed again. When he received no response, he halted power to the drill line and radioed for help to check on the exit pit worker. Workers discovered the victim’s body wrapped around the drill rod just ahead of the reamer.
Pulling in drill rods: Drill rods must be attached to a swivel to prevent rotation as they are pulled into the borehole. However, the area near the drill rods must be kept clear of personnel in case of swivel fail (lockup), which can cause unexpected movement or rotation of new the drill string.
Pulling in of product: Many final product installations utilize specialized equipment to handle rolls of HDPE or heavy cable. These products have memory and will curl as they leave the spool or are cut, and they can release tremendous energy and strike a worker causing injury. Other products present a crushing hazard due to weight.
Next time you see an HDD crew working on the way to your drill site, tip your hat or give them a wave because there is a lot more going on than meets the eye.