Horizontal earth boring (HEB) is a trenchless method used to install a pipe or a pipe casing in which other utilities will eventually be inserted. The process involves simultaneously jacking a pipe or pipe casing through the earth while removing the spoil by means of a rotating auger. Although boring operations have been used for decades and are considered to be safe when performed properly, there are potential hazards that must be addressed before and during the process.

Utility Damage Prevention

Before proceeding with any type of trenchless method, all utilities crossing the center line of the bore or in the immediate vicinity of the bore should be identified. Dig Safe call centers should be notified at least 24 to 72 hours (check state One-Call laws) prior to starting work. After the utilities are identified, it is extremely important to determine the exact location and depth of utilities that cross the bore path. Damaging a gas, electric or water line can have serious consequences, including injuries to workers and/or the public. Call before you dig!

Protective Systems

HEB requires the excavation of boring and receiving pits.

As with any excavation, precautions must be taken to ensure that they will not cave in and bury a workers. In brief, HEB contractors must comply with the same trenching and excavation rules as open-cut contractors. OSHA and state regulations require that protective systems be installed in the form of shoring, trench boxes or sloping. They must be properly installed and maintained. Additionally, there must be a Competent Person on the job, and that person must ensure that the job remains safe as it progresses by means of daily and as-needed inspections.

Fall Protection

Before a pit is dug, consideration should be given to ensuring that no one will fall into it. Such a fall can result in serious injuries, not only from the fall itself, but also from landing on machinery, tools and/or materials that will eventually be in the pit. Since OSHA Subpart M is not specific with regard to HEB operations, contractors have some options.

It has, for example, been suggested that all pits should be surrounded by a fence or barricades to keep unauthorized people away from excavation. If the pit is over 6 ft deep, some form of fall protection system must be put in place to ensure worker safety. The most reliable form of fall protection is a guard rail system that surrounds the edge. Whether constructed of wood, steel pipe, cables or other material, the system must be able to support 200 lbs in an inward/downward direction. The top rail or cable would have to be 42 in. ± 3 in. above the ground with a midrail or barricade approximately half way up. Cable systems should not deflect more than 3 in. at any point.

A controlled access zone (CAZ) — an area where certain work can take place without the use of a guardrail system — is another option. However, before establishing a CAZ the contractor must be able to demonstrate that it is infeasible or it creates a greater hazard to use conventional fall protection equipment such as guardrails, personal fall arrest system or motion stopping system. The CAZ plan will have to be created by a qualified person and supervised by Competent Persons who are trained and knowledgeable about fall protection. Individuals who are authorized to enter the CAZ must be identified in the written plan, which should be jobsite-specific and available at the jobsite.
Once a CAZ has been set up it must be surrounded by a control line not less than 6 ft or more than 25 ft from the unprotected edge of the pit. Control lines must be adequately supported and flagged or otherwise clearly marked at not more than 6-ft intervals. If authorized workers are permitted inside the control lines, they must be trained and assigned a Competent Person (with no other duties to monitor).

Hazardous Atmosphere

The OSHA Excavation Standard–Subpart P states that “every excavation where a hazardous atmosphere exists or could reasonably be expected to exist” shall be tested and monitored with an air monitor to prevent employee exposure to a harmful atmosphere such as oxygen deficiency, explosive methane or hydrogen sulfide. Boring pits, especially deep ones, have the potential to contain a harmful atmosphere.

To avoid worker exposure to a hazardous atmosphere created by these and other potential scenarios, it has been suggested that contractors regularly test the air in the pit and ventilate when necessary.

Confined Space Entry

On occasion it may be necessary to retract the auger and require a worker(s) to enter the casing to check the line and grade or to remove an obstruction. Whenever a worker(s) must enter the casing the situation must be treated as a confined space entry and the atmosphere must be tested prior to and during entry into the casing. The casing will also have to be ventilated with a blower and lighting provided. Anklets attached to a proper retrieval line should be attached to the workers in case a rescue becomes necessary.

Material Handling

Machinery, pipes, augers, spoil material and the like must be moved around, into and out of the boring pit. Each job is different and may require a different type of plan for material handling. Start by making sure that the equipment that will be used to lift and handle material is in good condition, starting with the crane or excavator. Daily inspections must be performed. Riggers should be instructed how to inspect and use slings and the different types of hitches to use so that a pipe or auger or some other object does not slip out of the sling and fall on workers below in the pit. Make sure the slings are rated to handle the weight of the load.

Casings are generally lifted and lowered into the trench with the auger inside the casing; therefore it should be secured inside so that it does not slip out. In addition to lifting and lowering materials, pipes and augers must be set in place.

During these operations workers should be aware of the pinpoint hazards when connecting the casings or attaching the augers. Tag lines should be used to control loads and keep them from swinging out of control. Workers should be directed to stand to one side and out from under loads as they are lifted into and out of the pit.

Welding

All the typical hazards associated with welding operations exist with one added factor — welding is being performed in an enclosed space. Depending on the size of the casing or pipe to be welded, one or two welders will be required to perform the task. They must be equipped with welding hoods, proper eye protection and welder’s leathers. Other workers who remain in the pit will also have to have proper eye protection to prevent flash burns. Some contractors provide a welding screen to block the rays from exposed workers; others require unnecessary personnel to exit the pit during welding operations. Ventilation, preferably local exhaust ventilation in deep trenches, must be provided to ensure that a safe atmosphere exists in the pit.

Other typical welding and cutting precautions will have to be in place such as properly storing and capping gas cylinders, removing gas hoses from the pit when not in use, grounding arc welding machines and using connectors that are not damaged. Remember that arc welding in a wet or damp environments increases electrical hazards, which is why it is so important to ensure that welding cables are in good condition and free from cuts and splices. Note: OSHA 1926.353(b) requires ventilation when welding or cutting in a confined space.

HEB Machine

Qualified and skilled HEB machine operators are key to the success of any pipe boring operation. They must have a feel for operating the machine because they cannot see what is in front of the auger even after core soil samples have been analyzed and bore charts provided. If the auger hits an undetected object and the operator does not realize that the machine’s torque is increasing, it is possible for the machine to tilt or flip over. Employees working in the pit must understand the potential hazards of working near the machine and take the appropriate precautions — e.g., keeping their hands and feet where they cannot be pinched between the rail and the pipe and other pinch points. They must also stay out from in front of the spoil ejection chute, especially when the bore takes place in gravel and sandy soil conditions. Workers should also be required to wear eye protection at all times.

Work Zones

Because HEB is often performed in areas near roadways, traffic control is a major consideration. Contractors should refer to the Manual of Uniform Traffic Control Devices (MUTCD) — Part VI when setting up work zones. Jersey barriers and other traffic control devices should comply with the requirements established by the MUTCD. Many DOT jobsites require workers to wear high visibility clothing — either Class II or III. It should fit properly and be properly secured to ensure visibility and eliminate the possibility of it being caught in moving machinery.

For more information about auger boring and other trenchless methods, consult NUCA’s Trenchless Construction Methods and Soil Compatibility Manual, which is available through the NUCA Store at www.nuca.com.

Note: Since in some cases there are no specific regulations or even industry-wide best practice recommendations regarding HEB hazard control, I asked several NUCA contractor members for suggestions. The NUCA contractor members consulted in the writing of this article were: Brandon Young, Vice President of Operations, Miller the Driller, Des Moines, Iowa; Jim Gonzales, Gonzales Boring & Tunneling Inc., North Plains, Ore.; LD Alexander, Safety Director, RMCI Inc., Albuquerque, N.M.; and Greg Strudwick, President, Greg Strudwick & Associates, Coppell, Texas.

Please keep in mind that the efficacy of the suggestions may vary based on the type, depth, soil condition and area of the country where the work is performed.

George Kennedy is NUCA Vice President of Safety.