Subsurface Drilling and Sampling AHA (Activity Hazard Analysis / Job Hazard Analysis)
Updated 2026-06-23
A Subsurface Drilling and Sampling AHA (Activity Hazard Analysis / Job Hazard Analysis) is the plan that keeps the drilling crew safe from the rotating drill string and caught-in hazard, from utility strikes during boring, and from the mast overhead and sampling hazards. Subsurface drilling and sampling advances borings and collects subsurface samples — combining the rotating-drill-string and caught-in hazard, the utility-strike and boring-clearance hazard, and the mast-overhead and sampling hazard. This guide walks through building a Subsurface Drilling and Sampling AHA that names the rotating-drill-string/caught-in, utility-strike/boring- clearance, and mast-overhead/sampling hazards and assigns the rotating-equipment, utility, and mast controls that hold up in the field.
Why subsurface drilling and sampling needs its own AHA
Subsurface drilling and sampling is the specific activity of advancing borings with a drill rig and collecting subsurface samples — operating the drill rig, advancing the drill string/augers, performing standard penetration testing (SPT), collecting split-spoon and undisturbed samples, and installing casing or wells. The defining feature is the operation of the drill rig with its rotating drill string, which is the primary hazard, along with the ground penetration (utility strike) and the mast. The hazards combine the rotating-drill-string and caught-in (the drill rig's rotating drill string, augers, and rotating components — a major caught-in and entanglement hazard (the rotating drill string can catch clothing, gloves, or a person, causing severe/fatal injury)), the utility-strike and boring-clearance (advancing borings penetrates the ground — the utility-strike hazard, requiring locating and clearing each boring before drilling), the mast-overhead and sampling (the drill rig's mast (raised near overhead power lines — electrocution), and the sampling operations (hammer/weight for SPT, handling samples)), and the pinch/lifting. The rotating-drill-string/caught-in and the utility-strike/boring- clearance justify a dedicated AHA.
Breaking subsurface drilling and sampling into steps
The steps for a Subsurface Drilling and Sampling AHA follow the drilling:
- Locate and clear the boring location (utilities)
- Position the rig and check overhead clearance
- Raise the mast (overhead clearance)
- Advance the boring (rotating drill string — stay clear)
- Perform the sampling/testing (SPT, split-spoon)
- Manage the rotating-equipment, utility, and mast hazards
- Complete and secure the boring
- Document
Each step carries a hazard, and the rotating-drill-string/caught-in, the utility-strike/boring-clearance, and the mast-overhead/sampling are where the most significant risks concentrate.
The hazards step by step
Rotating-drill-string and caught-in
The drill rig's rotating drill string, augers, and rotating components — a major caught-in and entanglement hazard (the rotating drill string can catch clothing, gloves, or a person, causing severe/fatal injury). The controls are keeping clear of the rotating drill string/augers (no loose clothing, no gloves that can catch, no reaching toward rotating components, staying clear of the rotating zone), knowing and using the emergency-stop/ kill controls, guarding where provided, qualified rig operation, and the caught-in controls. The rotating-drill- string/caught-in is the primary defining hazard — the rotating drill string is a severe caught-in/entanglement hazard. (These follow the rotating-equipment fundamentals.)
Utility-strike and boring-clearance
Advancing borings penetrates the ground — the utility-strike hazard, requiring locating and clearing each boring before drilling. The controls are locating utilities and clearing each boring (hand-clearing/vacuum-excavating the top of each boring before drilling — the critical control), awareness of underground hazards, and the utility/clearance controls. The utility-strike/boring-clearance is a defining hazard — drilling into a utility is serious. (These follow the ground-disturbance fundamentals.)
Mast-overhead and sampling
The drill rig's mast (raised near overhead power lines — electrocution), and the sampling operations (hammer/ weight for SPT, handling samples). The controls are overhead-clearance checks before raising the mast (the mast near overhead power lines is a serious electrocution hazard — maintain clearance), safe SPT/sampling (managing the SPT hammer, safe sample handling), and the mast/sampling controls. The mast-overhead/sampling is a defining hazard — the mast near power lines is an electrocution hazard. (These follow the overhead-power-line fundamentals.)
Pinch/lifting
The pinch and lifting (handling drill rods, casing, tooling) carries the pinch/lifting hazard. The controls are safe handling of drill rods/casing (pinch points, manual handling), and the ergonomic controls. (These follow the material-handling fundamentals.)
A simple Subsurface Drilling and Sampling AHA structure
| Step | Hazard | Control | Standard |
|---|---|---|---|
| Locate/clear | Utility strike | Locate and clear the boring location | project |
| Position rig | Overhead | Position rig, check overhead clearance | OSHA 1926.1408 |
| Raise mast | Electrocution | Overhead-clearance check before raising mast | OSHA 1926.1408 |
| Advance boring | Caught-in | Keep clear of rotating drill string, kill controls | project |
| Sample/test | Impact / handling | Safe SPT/sampling, safe sample handling | project |
| Secure | Open hole | Complete and secure the boring | project |
Rotating-drill-string safety and utility/mast control
A Subsurface Drilling and Sampling AHA centers on rotating-drill-string safety and utility/mast control. The rotating-drill-string safety addresses the drill rig's rotating components — controlled by keeping clear of the rotating drill string/augers (no loose clothing, no gloves that can catch, no reaching toward rotating components), knowing and using the emergency-stop/kill controls, guarding where provided, and qualified rig operation. The utility/mast control addresses the ground penetration and the mast — controlled by locating and clearing each boring before drilling, and overhead-clearance checks before raising the mast (near power lines). And the drill rods and sampling get handling controls. An AHA built on rotating-drill-string safety and utility/ mast control, with handling controls, addresses the hazards that define subsurface drilling and sampling.
From the field: what actually goes wrong
In fourteen years across federal, heavy civil, and industrial projects, subsurface drilling and sampling is the hands-on drilling activity, and its single most serious hazard is the rotating drill string. The rotating-drill-string and caught-in hazard is the primary defining concern — the drill rig's rotating drill string, augers, and rotating components turn with great force, and they are a major caught-in and entanglement hazard: the rotating drill string can catch loose clothing, gloves, a sleeve, or a person, and once it catches, it wraps and pulls with force that causes severe and often fatal injuries. This is one of the classic drilling-industry fatalities. So the controls are strict: keeping clear of the rotating drill string and augers (no loose clothing, no gloves that can catch in the rotating string, no reaching toward the rotating components, and staying out of the rotating zone), knowing and using the emergency-stop and kill controls, guarding where provided, and qualified rig operation. The rule "never wear gloves or loose clothing near a rotating drill string" exists because gloves and sleeves are exactly what the string catches.
The utility-strike/boring-clearance and the mast-overhead/sampling are the other defining hazards. On the projects I have run, advancing borings penetrates the ground, so drilling into a buried utility is a serious hazard, which makes locating utilities and clearing each boring (hand-clearing or vacuum-excavating the top of each boring before drilling) the critical control, the same as in the broader subsurface investigation. And the mast-overhead hazard is specific and serious: the drill rig's mast is raised to a significant height, and if it is raised near overhead power lines, it can contact them and cause electrocution, so overhead-clearance checks before raising the mast (identifying overhead power lines and maintaining clearance) are essential. Raising a mast into a power line is a known drill-rig fatality, so the overhead check before raising is a critical step. The sampling operations (managing the SPT hammer and weight, and handling the samples) and the pinch and lifting hazards of handling drill rods and casing round it out. The AHA built on rotating-drill-string safety and utility/mast control is the one that protects the drilling crew.
The bottom line
A Subsurface Drilling and Sampling AHA names the rotating-drill-string/caught-in, the utility-strike/boring- clearance, and the mast-overhead/sampling hazards with specific controls — keeping clear of the rotating drill string with no loose clothing or catch-prone gloves (the severe caught-in hazard), locating and clearing each boring before drilling, and overhead-clearance checks before raising the mast near power lines. The rotating- drill-string safety and the utility/mast control are the defining concerns. The AHA that manages both is the one that protects the crew.
Frequently asked questions
Why is the rotating drill string the most serious hazard?
The drill rig's rotating drill string, augers, and rotating components turn with great force and are a major caught-in and entanglement hazard — they can catch loose clothing, gloves, a sleeve, or a person, and once caught, wrap and pull with force that causes severe and often fatal injuries (a classic drilling fatality). Controls are keeping clear of the rotating drill string/augers (no loose clothing, no gloves that can catch, no reaching toward rotating components, staying out of the rotating zone), knowing and using the emergency-stop/kill controls, guarding where provided, qualified rig operation, and the caught-in controls.
Why is the mast an electrocution hazard?
The drill rig's mast is raised to a significant height, and if raised near overhead power lines, it can contact them and cause electrocution (a known drill-rig fatality). Controls are overhead-clearance checks before raising the mast (identifying overhead power lines and maintaining clearance), and the mast controls.
Why clear each boring before drilling?
Advancing borings penetrates the ground, so drilling into a buried utility is a serious hazard. Controls are locating utilities and clearing each boring (hand-clearing/vacuum-excavating the top of each boring before drilling — the critical control), awareness of underground hazards, and the utility/clearance controls.
What is subsurface drilling and sampling?
Subsurface drilling and sampling advances borings with a drill rig and collects subsurface samples — operating the rig, advancing the drill string/augers, performing standard penetration testing, collecting split-spoon and undisturbed samples, and installing casing or wells. Because it operates a rotating drill string (caught-in), penetrates the ground (utility strike), and raises a mast (overhead electrocution), those hazards apply.
Related AHAs and JHAs
- Geotechnical Investigations AHA — the broader geotechnical investigation
- Subsurface Investigation AHA — the related subsurface investigation
- Exploratory Excavations AHA — the related exploratory excavation
- Core Drilling and Concrete Saw Cutting JHA — related drilling fundamentals
Written by Mustafa Tok, CSP, ASP, CHST — OSHA Authorized Outreach Trainer with 14+ years of international construction safety experience across federal, heavy civil, and industrial projects.