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Underground utility installation — trenching for water, sewer, storm, gas, electrical duct banks, and communication lines — is one of the most frequently cited definable features of work (DFOW) on federal construction projects, and one of the few where a single missed control (an unverified utility locate, an unprotected trench wall) can kill a worker in seconds. On USACE and NAVFAC contracts this work falls squarely under EM 385-1-1 Chapter 25, Excavation and Trenching, with Chapter 34 (Confined Space) governing manhole and vault entry and Chapter 12 (Control of Hazardous Energy) governing tie-ins to live systems.
This activity hazard analysis example is written for SSHOs, project engineers, and quality control managers who need a defensible starting point before the preparatory meeting. Under the 2024 manual, the AHA for excavation and trenching work must be developed by the designated Competent Person (para 25-6), must document the CP's identification and credentials (25-6.c), and must address piping-connection ergonomic exposure, egress methods and locations, and the CP's ground examination (25-6.a, 25-6.b, 25-6.d). Any excavation 5 feet or deeper also triggers a separate Excavation and Trenching Plan (para 25-7), of which the AHA is a required component.
The example below follows the ENG Form 6206 (SEP 2024) structure: sequenced job steps with hazards, hierarchy-of-controls mitigation, and residual Risk Assessment Codes, plus the equipment, training, and inspection tables. All citations are to EM 385-1-1, 15 March 2024 — if your contract was awarded from a solicitation issued before 15 March 2024 it likely remains under the 2014 edition, whose paragraph numbering (e.g., 01.A.14) is completely different, so confirm the applicable edition before you copy any cite.
Risk Assessment Code (RAC) Matrix — EM 385-1-1 (2024)
Severity ↓ / Probability →
Frequent
Likely
Occasional
Seldom
Unlikely
Catastrophic
E
E
H
H
M
Critical
E
H
H
M
L
Moderate
H
M
M
L
L
Negligible
M
L
L
L
L
E = Extremely High Risk · H = High Risk · M = Medium Risk · L = Low Risk
(per EM 385-1-1 2024, para 2-2.u/2-2.w and ENG Form 6206). Controls must reduce the
residual RAC to a level the approval authority accepts before work proceeds.
Sample AHA: Underground Utility Installation
On a phone, swipe the table sideways to see the controls
and residual RAC columns →
Overall RAC:M — Medium Risk (highest residual step RAC, per EM 385-1-1 2024 para 2-6.d(4)(f))
Obtain a dig permit from the installation public works organization or other authority having jurisdiction before starting any excavation work, processed through the USACE supervisor, KO, or COR (25-8.f(1))
Contact utility companies and responsible authorities (811 one-call plus the installation utility shop) to locate and mark all underground utilities, and allow them to direct or assist with protection (25-8.f(2))
Review as-built drawings and supplement marks with independent locating (electromagnetic locator or ground-penetrating radar) where records are incomplete
Have the Excavation CP develop the Excavation and Trenching Plan for any excavation 5 ft or deeper and submit it for approval/acceptance before work begins (25-7)
L
Encountering unexploded ordnance (UXO) on former range or munitions response areas
Where explosives, unexploded munitions, or military ordnance are known or suspected, obtain certification that surface and subsurface UXO has been surveyed, cleared, and disposed of by UXO disposal personnel before excavating (25-7.g, 25-8.g(2))
If a suspect item is uncovered, stop work, evacuate the area, and notify the KO/COR and installation emergency services
L
Site setup, traffic control, and perimeter protection
Public, vehicles, or equipment falling into the open excavation
Install Class I perimeter protection (guardrail system per Ch 21) where the excavation is exposed to the public or to vehicles/equipment; protection guarding against traffic must be designed by a Qualified Person to withstand impact forces (25-8.h(1))
Install substantial stop logs or barricades where vehicles or mobile equipment operate adjacent to the excavation, and use a ground guide (25-8.e(1))
Implement the traffic control measures identified in the Excavation and Trenching Plan (25-7.c(6))
L
Workers struck by delivery trucks and equipment during offloading
Keep workers clear of vehicles being loaded or unloaded to avoid being struck by spillage or falling material (25-8.e(2))
Require high-visibility apparel for all employees exposed to equipment or vehicular traffic (25-8.e(4))
Use a dedicated ground guide and an exclusion zone around swing radii
L
Mechanical excavation with potholing near marked utilities
Excavator contact with an energized electrical line or pressurized gas line
Physically verify utility location by non-destructive means (hand digging or vacuum excavation) before any mechanical excavation within 3 ft of the marked location, and neutralize the utility system (25-8.f(3))
Excavate with caution as operations approach the utility location until the exact location is found (25-8.f(4))
Protect workers from the utility and protect the exposed utility from damage or displacement with supports and barriers (25-8.f, 25-8.f(5))
If an unidentified line is struck, evacuate the trench, stop equipment, and notify the utility owner and emergency services before resuming work
M
Cave-in of trench walls during excavation
CP inspects and tests soil conditions to classify the soil before the start of each shift and as conditions warrant, and documents the results (25-5.b)
Slope, bench, shore, or shield every excavation 5 ft or deeper; do not enter unprotected trenches (25-8.a)
Place spoil and materials at least 2 ft from the excavation edge or retain them so they cannot fall in (25-8.d(3))
CP conducts documented inspections before each shift, throughout the shift, and after every rainstorm or hazard-increasing event (25-5.a)
M
Workers struck by excavator bucket or suspended loads
Do not raise, lower, or swing loads over or adjacent to personnel in the excavation without substantial overhead protection; keep personnel at a safe distance until the load is placed (25-8.e(3))
Treat any excavator hoisting rigged loads as load handling equipment and follow Ch 16 (25-8.e Note)
Maintain positive communication between the operator and a designated ground guide
L
Install protective systems and enter the trench
Protective system failure or cave-in during entry
Install trench shields and shoring according to the manufacturer's tabulated data; sloping, benching, or shoring for excavations over 20 ft deep must be designed by a Registered Professional Engineer (25-7.c(2))
CP examines any damaged protective system material or equipment to evaluate suitability for continued use before it goes back in service (25-4.a(5))
Keep all workers inside the protected zone of the shield; never enter the trench outside the box
If evidence of possible cave-in, protective system failure, or other hazardous condition appears, remove workers and stop all work in the excavation until precautions are implemented (25-8.a(7))
M
Fall into trench or inability to exit quickly
Provide stairs, ramps, or ladders in excavations over 4 ft deep, spaced so no more than 25 ft of lateral travel is required, with at least two means of exit (25-8.h(5))
Extend access ladders from the trench bottom to at least 3 ft above the surface (25-8.h(7))
Provide walkways or bridges with standard guardrails where personnel or equipment cross the excavation (25-8.h(4))
L
Hazardous atmosphere in the trench (sewer gas, fuel-contaminated soil, oxygen deficiency)
Test the air before the start of each shift, or more often if directed by the CP, in excavations 4 ft or deeper where oxygen deficiency or gaseous conditions are known or suspected, and maintain a log of results at the work site (25-5.c)
Ventilate the trench and re-test before re-entry when readings exceed action levels
CP evaluates the need for continued air monitoring as work progresses (25-4.a(7))
L
Water accumulation undermining trench walls
Use diversion ditches, dikes, or other means to keep surface water out of the excavation (25-8.c(1))
Do not work in the excavation while water is accumulating unless the hazard is controlled (25-8.c(2)); an RPE must plan and direct pumping or drainage measures (25-8.c(2)(a))
Provide emergency power and CP monitoring when continuous groundwater control equipment is required (25-8.c(2)(b)); see the companion dewatering AHA
L
Pipe and conduit installation, bedding, and connections
Increased worker exposure during connection activities (bent over, kneeling, head-down in the trench)
Address workers' increased exposure during piping connection activities in this AHA as required by 25-6.a, including body position and reduced escape ability
Rotate connection tasks and use mechanical pipe-alignment aids to limit time spent kneeling below grade
Verify the protective system and egress locations before each connection sequence (25-6.b)
L
Struck-by or crushed-by during pipe hoisting and placement
Rig pipe with inspected slings and hardware per Ch 15; excavators hoisting rigged pipe are load handling equipment under Ch 16 (25-8.e Note)
Keep all personnel out of the trench and clear of the load path until the pipe is landed and blocked; use taglines for control (25-8.e(3))
Chock and block stockpiled pipe so it cannot roll into the excavation (25-8.d(2))
L
Tie-in to existing energized or pressurized utilities
Uncontrolled release of hazardous energy (electrical contact, pressurized water/gas release) when breaking into a live system
Attach the equipment-specific Hazard Isolation Procedure (HIP) to this AHA and reference it; an AHA by itself is not a HIP (12-6.a)
Submit the AHA and HIP to the KO or COR for acceptance before performing tie-in work (12-6.c)
Apply lockout/tagout under the Site-Specific Energy Control Plan by trained Authorized Individuals (12-7.a, 12-3), and verify that isolation and de-energization have been accomplished before opening the system (12-8.b(6)(e))
Neutralize the utility system before working within 3 ft of it (25-8.f(3)) and coordinate shutdowns with the utility owner through the USACE supervisor/KO/COR
M
Manhole and vault entry (confined space work)
Hazardous atmosphere, engulfment, or entrapment inside manholes and utility vaults
Treat manholes and vaults as confined spaces and follow Ch 34 entry procedures, including the permit process and an Attendant maintaining communication with Entrants (25-8.g(1), Ch 34)
Use only personnel trained as Entrants, Attendants, and Entry Supervisors per 34-3
Conduct documented pre-entry inspections of atmospheric testing and monitoring equipment (with calibration documentation), ventilation equipment, retrieval/rescue equipment, and access ladders (34-5.a, 34-5.b, 34-5.f, 34-5.h)
Install an isolation barrier to prevent liquids or free-flowing solids from entering the space during the work (34-8.g(2)), and lock out and tag out energized equipment serving the space per Ch 12
Stage non-entry retrieval equipment (tripod and winch) and confirm rescue procedures before entry (25-7.i)
M
Backfill, compaction, testing, and demobilization
Workers in the trench struck or buried during machine backfilling and compaction
Remove all personnel from the trench before machine backfilling over or adjacent to their position; maintain the protective system until workers are clear
Use a ground guide and high-visibility apparel for all work around compaction and loading equipment (25-8.e(1), 25-8.e(4))
Remove trench shields progressively as backfill rises; never pull shoring with workers in the unprotected excavation
L
Open excavations left accessible after work hours
Backfill excavations as soon as possible (25-8.h(3))
Barricade or cover all remaining pits, shafts, and similar openings (25-8.h(2))
Maintain perimeter protection and warning devices until final restoration is complete (25-8.h(1))
L
Equipment To Be Used
Hydraulic excavator / backhoe (also serves as LHE when hoisting rigged pipe — Ch 16)
Vacuum excavation truck or hand-digging tools for utility verification (25-8.f(3))
Lockout/tagout locks, tags, and isolation devices (Ch 12)
Class I/II/III perimeter protection, stop logs, and traffic control devices (25-8.e, 25-8.h)
Pipe rigging: slings, shackles, taglines (Ch 15)
Dewatering pump with emergency power source where continuous operation is required (25-8.c(2)(b))
PPE including high-visibility apparel (Ch 5, 25-8.e(4))
Training Requirements
Competent Person (Excavation): training, knowledge, and experience in soil analysis, use of protective systems, Ch 25, and 29 CFR 1926 Subpart P; able to detect cave-in conditions, protective system failures, and hazardous atmospheres; authority to stop work (25-3.a)
Rescue personnel trained on the rescue procedures identified in the Excavation and Trenching Plan (25-3.b, 25-7.i)
Confined space training for Entrants, Attendants, and Entry Supervisors, with retraining triggers per 34-3.a
Hazardous energy control training for Authorized Individuals on the SSECP and HIPs, including documented training records (12-3.a)
Equipment operator qualification for excavation machinery per 18-3 (referenced by 25-7.d)
AHA review and signature by every involved employee before starting work (2-6.d(2))
Inspection Requirements
CP documented inspection of each excavation, adjacent areas, and protective systems before each shift, throughout the shift as work dictates, after every rainstorm or hazard-increasing event, when fissures/sloughing/seepage/bulging appear, when size or spoil piles change, and on any indication of change in adjacent structures (25-5.a)
CP soil classification testing before the start of each shift and as conditions warrant, documented and maintained for the life of the project (25-5.b)
Air testing prior to each shift (or more often as the CP directs) in excavations 4 ft or deeper where oxygen deficiency or gaseous conditions are known or suspected, with a log maintained at the work site (25-5.c)
Documented pre-work inspection of confined space equipment: atmospheric monitor with calibration record, ventilation, PPE, fall protection, lighting, entry/egress ladders, barriers, and rescue equipment (34-5)
Periodic inspections of energy control procedures by an Authorized Individual not using the procedure being inspected (12-5.b)
Daily mobile equipment walk-around inspections per Ch 18
Competent / Qualified Person Requirements
Competent Person, Excavation — develops this AHA and the Excavation and Trenching Plan, performs soil classification and documented inspections, and must be onsite at all times while excavation or trenching work is performed (25-4.a, 25-4.a(9)); the AHA must identify the CP and their credentials (25-6.c)
Qualified Person — designs Class I perimeter protection against vehicle/equipment intrusion and equipment access ramps (25-4.b)
Registered Professional Engineer — required for sloping/benching or support system design over 20 ft depth, excavation below adjacent footings, and planning/directing dewatering measures (25-4.c)
Confined Space Entry Supervisor and trained Attendants/Entrants for manhole and vault entry (34-3.d, 34-3.e, 34-3.f)
Authorized Individuals for lockout/tagout under the Site-Specific Energy Control Plan (Ch 12, 12-3)
Applicable EM 385-1-1 (2024) Sections
Ch 25 — Excavation and Trenching
25-6 — Activity Hazard Analysis (AHA) Requirements — AHA developed by the Competent Person
25-7 — Minimum Plan Requirements — Excavation and Trenching Plan (mandatory at depths of 5 ft or more)
25-8.f — Underground Utilities — dig permits, utility locates, physical verification within 3 ft, neutralizing the utility
Ch 34 — Confined Space (manhole and vault entry)
Ch 12 — Control of Hazardous Energy (utility tie-ins)
Applicable OSHA Standards
29 CFR 1926 Subpart P (1926.650–.652) — Excavations
29 CFR 1926.652 — Requirements for protective systems
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What EM 385-1-1 chapter covers underground utility installation?
Chapter 25, Excavation and Trenching, is the governing chapter, with para 25-8.f specifically covering underground utilities — dig permits, utility locates, and physical verification within 3 ft of marks. Manhole and vault entry pulls in Chapter 34 (Confined Space), and tie-ins to energized or pressurized systems pull in Chapter 12 (Control of Hazardous Energy). OSHA's parallel requirements are 29 CFR 1926 Subpart P, especially 1926.651(b) for utility locates.
Do I need an Excavation and Trenching Plan in addition to the AHA?
Yes, whenever any excavation or trench reaches 5 ft or more in depth. Para 25-7 requires a plan developed by the Competent Person and approved by the USACE supervisor or accepted by the KO or COR before work begins, and the AHA is a required component of that plan (25-7.a). For excavations under 5 ft, or made entirely in stable rock, the plan is optional but the AHA is still required.
Who has to prepare this AHA?
Para 25-6 requires the AHA for all work in excavations and trenches to be developed by a Competent Person, not just any supervisor. The AHA must also identify the Excavation CP and their credentials (25-6.c), document the egress methods and locations (25-6.b), and document the CP's ground examination showing no indication of potential cave-in (25-6.d).
What should the overall RAC be for underground utility installation?
Under para 2-6.d(4)(f) the overall RAC must not be lower than the highest residual job step RAC on the AHA. For this activity that is typically M (Medium), because cave-in exposure and the possibility of striking an energized or pressurized utility remain credible even with protective systems, locates, and verification in place. If your controls cannot bring every step to at least M — for example, live gas tie-ins without a confirmed isolation — expect the approval authority to push back before accepting the AHA.
Does the 2014 or 2024 edition of EM 385-1-1 apply to my contract?
Solicitations issued on or after 15 March 2024 fall under the 2024 edition; contracts existing before that date generally remain under the 2014 edition until completion. The two editions number requirements completely differently — this page cites the 2024 chapter-paragraph style (e.g., 25-8.f), while the 2014 edition used section-letter cites (e.g., 25.A). Confirm the edition in your contract before reusing citations.
What does "physically verify within 3 feet" actually require?
Para 25-8.f(3) requires that when working within 3 ft of a marked underground utility you physically verify its location by non-destructive methods — hand digging or vacuum excavation, not the excavator bucket — and neutralize the utility system. Marks from the locate service establish where to pothole; they are not a license to dig mechanically up to the paint line. Para 25-8.f(4) additionally requires excavating with caution as you approach the utility until its exact location is found.