Excavation Safety

Responsibilities

Departments

Departments are expected to maintain safe and healthy living, learning, and working environments for faculty, staff, students, and visitors to our campus.

• Each department performing excavation work must appoint a "competent person(s)" to ensure compliance with this program. 
• Departments must ensure that all persons designated as competent persons have attended Environmental Health & Safety competent person training.
• Departments must ensure that all persons entering excavations greater than four feet deep have attended Environmental Health & Safety awareness level training.

Competent Persons

Competent persons designated by the department will perform the following tasks once they have received training from Environmental Health & Safety:

• Be familiar with soil analysis and determine the class of soil for each excavation.
• Determine the appropriate protective system needed to prevent a potential cave-in. Be familiar with protective systems and how to use them.
• Determine the appropriate methods to eliminate or control for all hazards, including protection from a potential cave-in.
• Conduct site inspections in accordance with the requirements outlined in this program and maintain necessary documentation.
• Ensure employee training for all employees entering excavations greater than four feet deep.
• Ensure appropriate personal protective equipment is provided and worn.

Employees

Employees who work in or around excavations must:

• Follow the requirements of this program.
• Attend required training.
• Wear assigned personal protective equipment.

Environmental Health & Safety

Environmental Health & Safety will provide technical support, competent person and awareness level training, and oversight for this program. Involvement by Environmental Health & Safety does not relieve the departments, supervisors, or contractors of their individual responsibilities. Environmental Health & Safety responsibilities for this program include:

• Developing, implementing, and administering the program.
• Training on all aspects of the program requirements and maintaining centralized records.
• Serving as a technical resource.
• Providing guidance on the selection of protective systems.
• Evaluating the overall effectiveness of the program on a periodic basis and making appropriate changes as needed to assure the safety of personnel.

Contractors

Contractors must comply with all local, state, and federal safety requirements, and must assure that all employees performing work on Virginia Tech property have been suitably trained and are provided appropriate personal protective equipment per the Safety Requirements for Contractors and Subcontractors program. Contractors performing excavation work on university property must coordinate their work with the Division of Campus Planning, Infrastructure, and Facilities and Miss Utilities to assure related activities, such as utility identification, location, and shutdown are addressed.

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Training

Excavation Awareness Training

Each employee required to enter an excavation greater than 4 feet deep must attend Environmental Health & Safety Excavation Awareness training prior to entry. Information regarding related hazards and methods of protection are covered.

Excavation Competent Person Training

Designated departmental competent persons who will be performing inspections and providing oversight must attend Environmental Health & Safety Excavation Competent Person training. Topics include:

• Hazards related to excavation work;
• Work practices and selection of protective systems;
• Methods of evaluating the site and conducting inspections;
• Requirements of this program and any related programs; and
• Emergency procedures.

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Excavation Assessment

Prior to personnel entering the excavation, and as necessary throughout the shift, the designated competent person must perform an assessment of the excavation to identify hazardous conditions and determine protective measures for personnel entering the excavation, personnel working in the vicinity of the excavation, and the general public, which may be inadvertently exposed to related hazards. This evaluation must be documented.

All hazards identified must be eliminated or controlled prior to personnel entering the excavation. The assessment shall be documented on the Excavation Assessment Form.

Instructions and guidance for performing the site evaluation and completing the Excavation Assessment Form are provided below.

Project Information

• Location: Specify the location of the excavation - street, nearest building, etc.
• Date/time: Specify the date and time that the excavation is being evaluated.
• Miss Utility ticket number: Specify the ticket number given by Miss Utility verifying that notification and approval to dig has been given.
• Date/time cleared: Specify the date and time that clearance was given by Miss Utility.

Excavation Depth

• Excavation depth: Check one of the boxes indicating the anticipated depth of the excavation and follow the required action specified:
  • If " < 4 feet or personnel will not be entering" is checked, contacting Miss Utility is the only action required. The remainder of the assessment form does not need to be completed, provided there are no additional hazards.
  • If "between 4 and 20 feet" is checked, all hazards must be identified and effectively controlled prior to personnel entering.
  • If " > 20 feet" is checked, the competent person must contact 540-231-2341 for additional review and compliance assurance.

Hazards and Controls

Protection against cave-in or trench collapse 

• Cave-in: any soil class: If a trench box will be used, check this box. Soil does not have to be analyzed and classified. The trench box must be appropriate for the excavation depth and used according to the manufacturer's recommendations. 
• Cave-in: assume Class C: If the excavation walls will be sloped or benched 34 degrees (i.e. 1 1/2 H to 1 V), check this box.
  • Note: This box cannot be checked if the excavation is a bell-bottom pier hole, protective systems for class "C" soil cannot be implemented, or timer or aluminum shoring will be installed. 
• Cave-in: all other situations: (includes class "A" or "B" soil, bell-bottom pier holes, and the use of aluminum or timber shoring systems). If one of the previous options cannot be selected and implemented, check this box. EHS and/or departmental safety representatives must be contacted for additional review. 

Protection against other hazards

• Surface encumbrances: All equipment, materials, supplies, permanent installations (e.g. buildings, roadways, sidewalks, trees, boulders, etc.) at the surface of the excavation that could present a hazard to personnel working in the excavation must be removed or supported, as necessary.
  • Check "N/A" if it is not applicable.
  • Check "Removed" if there are items that must be moved at least two feet from the edge of the excavation. 
  • Check "Supported" if shoring or other support is necessary to secure items. 
• Underground installations: Arrangements must be made, as necessary, by the competent person for the project with the appropriate utility agency for the protection, removal, shutdown/de-energization, or relocation of underground installations identified by the Miss Utility System. Check the appropriate control measure taken.
  • Work on such installations shall only be conducted by authorized personnel (i.e. the owner of the installation).
  • Work may proceed with caution, provided detection equipment or other safe and acceptable means (e.g. hand digging) are used to locate the utility as the excavation is opened and each underground installation is approached. 
• Access/egress: Stairs, ladders, or ramps must be provided where personnel must enter excavations four feet or more in-depth, and must comply with OSHA rules and regulations. The maximum distance of travel in excavation to a means of egress shall not exceed 25 feet. Check the appropriate box for the control measure selected.
• Vehicular traffic: Excavations affecting vehicular traffic must be barricaded and warnings provided to oncoming traffic. Additional precautions for personnel (i.e. high visibility warning vests, hard hats, etc.) may be required. Personnel designated to flag traffic must comply with the Virginia Department of Transportation's Flagger Certification program. This certification is available through Environmental Health & Safety. Check the appropriate box for the control measure selected.
• Falling loads: Personnel shall not be permitted underneath loads handled by lifting or digging equipment. All personnel is required to stand away from any vehicle being loaded or unloaded. Vehicle operators may remain in the cab of the vehicle being loaded or unloaded by lifting/digging equipment provided the vehicle cab is reinforced or otherwise adequately protected from impact. Check the box to verify that personnel has been informed to stay clear of loading equipment.
• Mobile equipment: When mobile equipment is operated adjacent to the edge of an excavation, a warning system must be used when the operator does not have a clear and direct view of the edge of the excavation. The warning system may consist of barricades, hand or mechanical signals, signs/flags, or stop logs. If possible, the surface grade should slope away from the excavation. Check the type of warning system to be used.
• Hazardous atmosphere: Atmospheric testing must be conducted in excavations over four feet deep where a hazardous atmosphere could reasonably be expected to exist, such as near landfill areas, near hazardous substance storage, near gas pipelines, or whenever hazardous chemicals will be used in the excavation. This determination is made by the competent person during excavation evaluation and/or inspection. See information and guidelines for atmospheric testing.
  • Emergency rescue equipment, such as breathing apparatus, safety harness, and lifeline, or basket stretcher shall be readily available where hazardous atmospheric conditions exist or may reasonably be expected to develop during work in an excavation. This equipment shall be attended to when in use. 
• Water accumulation: Personnel is not permitted to work in excavations that contain, or are accumulating, water unless precautions have been taken to protect personnel from hazards posed by water accumulation. These precautions may include special support or shield systems to protect from a cave-in, water removal by mechanical pump to control the level of accumulating water, or the use of a safety harness and lifeline. Check the appropriate box for the control measure selected.
  • If water is controlled or prevented from accumulating by the use of water removal equipment, the equipment and operation must be monitored by a person familiar with the equipment.
  • If excavation work will interrupt the natural drainage of surface water (e.g. streams), diversion ditches, dikes, or other suitable means must be used to prevent surface water from entering the excavation. Precautions must also be taken to provide adequate drainage of the area adjacent to the excavation.
  • Excavations subject to runoff from heavy rains must be re-inspected by a competent person to determine if additional precautions are necessary. 
• Adjacent structures: Where the stability of adjoining buildings, walls, or other structures may be endangered by excavation operations, support systems (e.g. shoring, bracing, or underpinning) shall be provided to ensure the stability of the structure and provide adequate personnel protection. Excavations below the level of a base or footing of any foundation or retaining wall that could reasonably be expected to pose a hazard to personnel are not permitted unless:
  • A support system, such as underpinning, is provided to ensure the safety of personnel and the stability of the structure; or
  • A registered professional engineer has approved the determination that the structure is sufficiently removed from the excavation so as to be unaffected by the excavation activity; or
  • A registered professional engineer has approved the determination that such excavation work will not pose a hazard to employees.
    • Note: Where review or approval of a support system by a registered professional engineer is required, the competent person shall secure this in writing before work begins. A copy of this approval must be provided to Environmental Health & Safety upon request. 
• Loose rock or soil: Adequate protection must be provided to protect employees from loose rock, soil, or other materials that could pose a hazard by falling or rolling from an excavation face. Such protection may consist of:
  • Scaling to remove loose material;
  • Installation of protective barricades, such as wire mesh or timber on the face of the sloper, at appropriate intervals, to stop and contain falling material;
  • Sufficient benching to contain falling material;
  • Keeping materials or equipment at least two feet from the edge of the excavation; and/or
  • Use of restraining devices that are sufficient to prevent materials or equipment from falling or rolling into the excavation. 
• Fall protection: Standard guardrails, fences, or barricades must be provided for excavations adjacent to walkways, driveways, and other pedestrian or vehicle thoroughfares. Walkways or bridges for public and site personnel to cross over excavations must be provided when the excavation width is greater than 30 inches, and depth is greater than four feet. Walkways or bridges must have standard guardrails and be at least 19inches in width. If the walkway will serve the general public, it must be at least 36 inches in width, or the width of the building exit door(s) if serving as the exit for that building, whichever is greater. Where personnel will be working or passing under such walkways, a toe-board must be installed on the walkway. Wells, holes, pits, shafts, and similar excavations must be effectively barricaded or covered and posted (as necessary) to prevent unauthorized access. All temporary excavations of this type must be backfilled as soon as possible. 
• Security: When an excavation will be left open overnight, barricades and/or fencing to restrict access, warning signs, and adequate lighting shall be provided as necessary to protect the public.
• Personal protective equipment: Indicate the minimum personal protective equipment, associated with excavation hazards, required for entry into the excavation.

Entry Authorization

• Competent Person: Once the competent person has evaluated site conditions and necessary control measures have been implemented, the competent person shall sign the Excavation Assessment Form and post it at the entrance to the excavation, or other central location.
  •  Personnel shall not enter the excavation until this assessment has been completed, control measures implemented, and entry has been authorized on the form. 
  • All entrants must review the information provided on the assessment form so that hazards are known and protective measures understood. 
  • If any of the controls identified on the form have been altered, removed, or damaged entry should not occur until the competent person has re-evaluated the situations and corrective measures have been taken. 
• In case of emergency: Call 911 immediately. Personnel shall have a means for contacting emergency services in the event of an emergency. Phone numbers for on and off-campus phones are provided on the form. When radio contact is the primary means of communication, personnel must be available at the base station with a phone system available.

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Protective Systems

Each employee in an excavation shall be protected from a cave-in by using either an adequate sloping/benching system or an adequate support/protective system.

Exceptions to this requirement are limited to:

• Excavations made in stable rock; 
  • Note: "Stable rock" is not recognized by Virginia Occupational Safety and Health (VOSH) in the commonwealth and should not be considered as an option. 
• Excavations less than 5 feet in depth where examination of the ground by a Competent Person provides no indication of a potential cave-in.

Protective systems shall be capable of resisting all loads that could be reasonably expected to be applied to the system.

Trench Boxes (Best Practice)

Trench boxes are pre-built shield systems designed to the manufacturer's tabulated data. These boxes must be used in accordance with all specifications, recommendations, and limitations issued or made by the manufacturer. A copy of the manufacturer's instructions must be available for review, upon request.

• Trench boxes must not be used at a depth greater than that for which they were designed. 
• The shield must be installed in a safe manner to restrict lateral or another hazardous movement of the shield in the event of a sudden cave-in. The closer a properly constructed trench shield/box is to the trench wall, the less chance that it could be dislodged by a lateral force.
• Personnel shall not be allowed in trench boxes when they are being installed, removed, or moved vertically/horizontally (where hazardous).
• Personnel shall not work outside of the protective structure of the trench box where protective systems are not provided.

Sloping and Benching

Sloping and benching system requirements are specified below for excavations between 4 and 20 feet deep. The angle of the slope or bench is determined by the class of soil present at the excavation site. 

• (Best Practice) The competent person may assume the worst class of soil (i.e. the most unstable), class "C", and angle the sides of the excavation 34 degrees (i.e. 1 1/2 H to 1 V).
• If the competent person has classified the soil and determined that it is class "B," the angle of the sides of the excavation must be 45 degrees (i.e. 1 H to 1 V). 
• Class "A" soil is not recognized at Virginia Tech because all soil has been previously disturbed, and therefore does not meet the criteria for class "A" soil properties. 

Personnel shall not be permitted to work above other personnel on the faces of sloped or benched protective systems except when personnel at lower levels are protected from the hazards of falling, rolling, or sliding materials or equipment.

For more information on sloping and benching systems - 29 CFR 1926, Subpart P, Appendix B. 

Support Systems

Where preassembled shield systems or sloping/benching is not available or feasible, the competent person must implement an appropriate system designed to OSHA criteria (i.e. timber or aluminum hydraulic shoring), or have written approval by a registered professional engineer to implement the system designed by him/her. 

For more information on timber shoring refer to 29 CFR 1926, Subpart P, Appendix C. 

For more information on aluminum hydraulic shoring refer to 29 CFR 1926, Subpart P, Appendix D.

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Site Inspections

Daily inspections

The departmental competent person shall conduct daily inspections of excavations, adjacent areas, and protective systems for evidence of a situation that could result in possible cave-ins, failure of protective systems, hazardous atmospheres, or other hazardous conditions. Daily inspections must be conducted by the competent person prior to the start of work or personnel entering the excavation each day and as needed throughout the shift. Inspection is especially critical on Mondays, where rain or other changing conditions occurring over the weekend may have deteriorated soil conditions and/or protective systems. If personnel will not be entering the excavation on a given day, inspection is not required.

The competent person shall maintain a written log of all inspections conducted. This log shall include the date, worksite location, results of the inspection, and a summary of any action taken to correct existing hazards. The back of the Excavation Assessment Form can be used to document inspections. Items to inspect include:

• Surface conditions:
  • No cracks along the top edge of the excavation;
  • Spoil piles, materials, and equipment are not within 2 feet of the edge of the excavation;
  • No standing water in the excavation; and/or
  • No sources of vibration .
• Banks and sides of slope/bench:
  • No cracks on the walls of the excavation;
  • No spalling (i.e. soil falling from the sides of the excavation into the excavation);
  • No changes in soil type; and/or
  • The slope remains adequate for the class of soil originally selected. 
• Shoring/shielding:
  • Shoring/shielding still in place and effective;
  • Hydraulic cylinders not leaking; and/or
  • Wedges remain tight. 
• Access/egress:
  • Stairs, ladders, or ramps for access/egress in place and secured, where applicable) 
• Existing utilities:
  • Utilities identified and protected;
  • Utilities de-energized or shut-off, where necessary; and/or 
  • Support is adequate. 
• Weather (which could affect the integrity of the soil or excavation):
  • No overnight freezing/thawing
  • No overnight rain (heavy)

Additional inspections

Inspections shall also be made after each hazard-changing event, such as heavy rains, where necessary. 

Where the competent person, or personnel entering the excavation, find evidence of a situation that could result in a possible cave-in, protective system failure, hazardous atmospheric conditions, or other hazardous conditions that may expose personnel shall evacuate the excavation until the situation has been evaluated and corrected.

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Emergencies

A typical trench collapse involves three to five cubic yards of soil or about 6,000 to 20,000 pounds. Hazardous effects include compression and asphyxiation. Typical extrication can take one to seven hours depending on the conditions of the cave-in. Individuals should not place themselves at risk in order to save the life of another.  Such situations too often lead to the death of the would-be-rescuer as well as the person originally in danger.  It is the intent of this program to minimize the associated risks with excavation work and focus on accident prevention.    

Blacksburg Volunteer Fire Department is the designated response agency for cave-in emergencies.  The first and most important action that can be taken in the event of a cave-in is to activate the emergency response system by calling 911.

Personnel at Virginia Tech are not trained, nor expected, to perform trench rescue.  However, there are several actions that can be taken to support the rescue team(s) and further protect on-site personnel.

• If the victim is not visible, try to identify the area where the victim most likely is located as closely as possible.
• Contact 540-231-4300 to request the vacuum truck (located at Virginia Tech Electric Service) be brought to the site.  
• Hand digging, if it is safe to approach the site, can begin immediately.  
  • Mechanical excavating equipment should not be used to dig the person out due to the potential for additional injury, crushing, or dismemberment.  
• Have someone meet the fire department upon their arrival and brief them on the situation.
• Assemble materials and equipment that may be beneficial during rescue operations, such as shovels, plywood/lumber, ladders, buckets, etc. 
• Clear the area so that rescue personnel has access to the site.

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Definitions

Accepted engineering practices: the standards of practice required by a registered professional engineer. 

Adjacent structure stability: to the stability of the foundation of adjacent structures whose location may create surcharges, changes in soil conditions, or other disruptions that have the potential to extend into the failure zone of the excavation.

Aluminum hydraulic shoring: a manufactured shoring system consisting of aluminum hydraulic cylinders (cross braces) used with vertical rails (uprights) or horizontal rails (wales). Such system is designed to support the sidewalls of an excavation and prevent cave-ins. 

Bell-bottom pier hole: a type of shaft or footing excavation, the bottom of which is made larger than the cross-section above to form a belled shape.

Benching or benching system: a method of protecting employees from cave-ins by excavating the sides of an excavation to form one or more horizontal steps, usually with vertical or near-vertical surfaces between levels.

Cave-in: the movement of soil or rock into an excavation, or the loss of soil from under a trench shield or support system, in amounts large enough to trap, bury, or injure and immobilize a person.

Cemented soil: a soil in which the particles are held together by a chemical agent, such as calcium carbonate, such that a hand-size sample cannot be crushed into powder or individual soil particles by finger pressure.

Class "A" soil: cohesive soils with an unconfined, compressive strength of 1.5 tons per square foot (tsf) (144 kPa) or greater. Examples of cohesive soils are clay, silty clay, sandy clay, clay loam, and, in some cases, silty clay loam and sandy clay loam. Cemented soils such as caliche and hardpan are also considered Type A. However, no soil is Type A if:

• The soil is fissured; or
• The soil is subject to vibration from heavy traffic, pile driving, or similar effects; or
• The soil has been previously disturbed; or
• The soil is part of a sloped, layered system where the layers dip into the excavation on a slope of four horizontal to one vertical (4H:1V) or greater; or
• The material is subject to other factors that would require it to be classified as a less stable material.

Class "B" soil:

• Cohesive soil with an unconfined compressive strength greater than 0.5 tsf (48 kPa) but less than 1.5 tsf (144 kPa); or
• Granular cohesionless soils including angular gravel (similar to crushed rock), silt, silt loam, sandy loam, and, in some cases, silty clay loam and sandy clay loam.
• Previously disturbed soils except those which would otherwise be classified as Type C soil.
• Soil that meets the unconfined compressive strength or cementation requirements for Type A, but is fissured or subject to vibration; or
• Dry rock that is not stable; or
• Material that is part of a sloped, layered system where the layers dip into the excavation on a slope less steep than four horizontal to one vertical (4H:1V), but only if the material would otherwise be classified as Type B.

Class "C" soil:

• Cohesive soil with an unconfined compressive strength of 0.5 tsf (48 kPa) or less; or
• Granular soils including gravel, sand, and loamy sand; or
• Submerged soil or soil from which water is freely seeping; or
• Submerged rock that is not stable, or
• Material in a sloped, layered system where the layers dip into the excavation or a slope of four horizontal to one vertical (4H:1V) or steeper.

Competent Person: one who has been trained to identify hazards in the workplace, or working conditions that are unsafe for employees, and who has the authority to have these hazards eliminated or controlled.

Cross braces: the horizontal members of a shoring system installed from side to side of the excavation. The cross braces bear against either uprights or wales. 

Excavation: any man-made cut, cavity, trench, or depression in an earth surface formed by earth removal.

Faces or sides: the vertical or inclined earth surfaces formed as a result of excavation work.

Failure: the movement or damage of a structural member or connection that makes it unable to support loads.

Hazardous atmosphere: an atmosphere that is explosive, flammable, poisonous, corrosive, oxidizing, irritating, oxygen-deficient, toxic, or otherwise harmful, that may cause death, illness, or injury.

Ingress and egress: "entry" and "exit" respectively and refer to the safe means for employees to enter or exit.

Kickout: the accidental movement or failure of a cross brace.

Protective system: a method of protecting employees from cave-ins, from material that could fall or roll from an excavation face into an excavation, or from the collapse of adjacent structures. Protective systems include support systems, sloping and benching systems, shield systems, and other systems that provide the necessary protection.

Ramp: an inclined walking or working surface that is used to gain access to one point from another. A ramp may be constructed from earth or from structural materials such as steel or wood.

Registered professional engineer: a person who is registered as a professional engineer in Virginia.

Sheeting: the members of a shoring system that retain the earth in position and in turn are supported by other members of the shoring system.

Shield or shield system: a structure used in excavation to withstand cave-ins and which will protect employees working within the shield system. Shields can be permanent structures or portable units moved along as work progresses.

Shoring or shoring system: a structure that is built or put in place to support the sides of an excavation to prevent cave-ins.

Sides: see "Faces."

Sloping or sloping system: sloping the sides of the excavation away from the excavation to protect employees from cave-ins. The required slope will vary with soil type, weather, and surface or near-surface loads that may affect the soil in the area of the trench (such as adjacent buildings, vehicles near the edge of the trench, and so forth).

Soil classification: see 29 CFR 1926, Subpart P, Appendix A.

Stable rock: natural solid mineral material that can be excavated with vertical sides that will remain intact while exposed.

Structural ramp: a ramp built of steel or wood, usually used for vehicle access. Ramps made of soil or rock are not considered structural ramps.

Support system: a structure such as underpinning, bracing, or shoring, which provides support to an adjacent structure, underground installation, or the sides of an excavation.

Surface encumbrances: include utilities, foundations, streams, water tables, transformer vaults, walkways, bridges, roads, and geologic anomalies.

Surcharge: an excessive vertical load or weight caused by spoil, overburden, vehicles, equipment, or activities that may affect stability.

Tabulated data: tables and charts approved by a registered professional engineer and used to design and construct a protective system.

Trench: a narrow excavation (in relation to its length) made below the surface of the ground.

Trench box or shield: See "Shield".

Unconfined compressive strength: the load per unit area at which soil will fail in compression.

Underground installations: include, but are not limited to, utilities, tunnels, shafts, vaults, foundations, and other underground fixtures or equipment that may be encountered during excavation work.

Uprights: the vertical members of a trench shoring system placed in contact with the earth and usually positioned so that individual members do not contact each other. Uprights placed so that individual members are closely spaced, in contact with, or interconnected to each other, are often called "sheeting."

Wales: horizontal members of a shoring system placed in the direction of the excavation face whose sides bear against the vertical members of the shoring system or earth (the uprights or sheeting).

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Documents

Excavation Assessment Form

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