1.0   INTRODUCTION

Excavation and trenching cave-ins result in more than one hundred fatalities annually in the United States. With little or no warning, an unsupported, improperly shored or sloped trench or excavation wall can collapse, trapping workers below in seconds. For each fatality there are an estimated fifty related serious injuries annually. In addition to human losses the financial costs can be enormous--property damage, work stoppage, and workers' compensation.

The purpose of this program is to protect employees from hazards that may be encountered while working in trenches and excavations. The program includes provisions for employee training, hazard identification and control, and safe work practices that must be followed while working in an excavation or trench. This program complies with Occupational Safety and Health Administration (OSHA) standard 29 CFR 1926 Subpart P.

2.0  SCOPE

This program applies to all open excavation made in the earth's surface, including trenches. It covers all employees that work in or around excavations.

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

Aluminum Hydraulic Shoring- a manufactured shoring system consisting of aluminum hydraulic cylinders (crossbraces) used with vertical rails (uprights) or horizontal rails (wales). This 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 in which the bottom is made larger than the cross section above to form a belled shape.

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

Cave-in- the sudden 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 a person.

Competent person- one who has been trained to identify hazards in the surroundings or working conditions and has the authority to have these hazards promptly corrected. For purposes of this standard, a competent person must have specific training in, and be knowledgeable about, soil analysis, protective systems, and the requirements of this standard. The competent person shall determine the means of protection (sloping back the sides of the excavation, use of trench shields, or shoring) that will be used for each excavation project.

Cross braces- the horizontal members of a shoring system installed perpendicular to the sides 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, corrosive, oxidizing, irritating, oxygen deficient, toxic, or otherwise harmful, that may cause death, illness, or injury.

Kickout- the accidental movement or failure of a crossbrace.

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

Ramp- an incline walking or working surface used to gain access to one point from another. A ramp is constructed of earth or structural materials such as steel or wood.

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- a structure that withstands cave-ins and protects employees working within the shield system. Shields can be permanent structures or portable units moved along as work progresses. Shields used in trenches are usually called "trench boxes" or "trench shields." Shields do not generally prevent cave-ins but protect employees if a cave-in occurs.

Shoring- a structure that supports the sides of an excavation to prevent cave-ins. Shoring systems may be hydraulic, mechanical, or made from timber.

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

Stable rock- natural solid mineral material that can be excavated with vertical sides that will remain intact while exposed. Rock which contains visible fractures or seams, or rock (e.g., shale) which is interlayed with clay or soil does not constitute stable rock.

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.

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

Trench- a narrow excavation (in relation to its length) made below the surface of the ground. In general, the depth is greater than the width. The width of a trench measured at the bottom is less than 15 feet.

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 spaced 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 parallel to the excavation face whose sides bear against the vertical members of the shoring system or earth (the uprights or sheeting).

4.0  GENERAL REQUIREMENTS

 Training

1. All personnel involved in excavation work shall be trained in the requirements of this program. Training will be conducted by the Safety Manager or other knowledgeable person.

2. Training shall be performed before the employee is assigned duties in excavations.

3. Retraining will be performed whenever a supervisor or the Safety Manager determines that an employee does not have the knowledge or skills to safely work in excavations.

4. Training records will be maintained in the Safety Office. These records shall include the date of the training program, the instructor, and a copy of the written material presented.

5. Appropriate training will include:

• Recognition of potential hazards.
• Safe work practices that must be followed while working in excavations.
• Personal protective equipment required during work in excavations.
• Procedures to be followed if a hazardous atmosphere exists or could reasonably be expected to develop.
• Emergency and non-entry rescue methods, and procedures for calling rescue service.
• Ladder safety.

Pre-work Site Inspection

1. Before excavation, the site will be thoroughly inspected by a competent person for any conditions requiring precautionary safety measures.

2. All equipment, materials, permanent installations, trees, and other objects at the surface that could present a hazard to employees working in the excavation shall be removed or supported as necessary.

Underground Installations

1. The location of sewers, telephones, fuel, electric, water lines, or any other underground installations that may be encountered shall be determined before opening an excavation.

2. If it is not possible to establish the exact location of these installations, the work may proceed with caution if detection equipment or other safe means are used to locate the utility.

3. Work shall be done in a manner that does not endanger underground installations or employees. While the excavation is open, underground installations shall be protected, supported, or removed to protect employees.

Stability of Adjacent Structures

1. Support systems (such as shoring, bracing, or underpinning) shall be used to assure the stability of structures and the protection of employees if excavation operations could affect the stability of adjoining buildings, walls, or other structures.

2. Excavation below the level of the base or footing of a foundation or retaining wall that could pose a hazard to employees shall not be allowed unless:

• A support system, such as underpinning, is provided to ensure the safety of employees and the stability of the structure or,
• The excavation is in stable rock or,
• A registered professional engineer has approved the determination that the structure is sufficiently removed from the excavation and will be unaffected by the excavation activity or,
• A registered professional engineer has approved the determination that the excavation work will not pose a hazard to employees.

3. Sidewalks, pavements, and collateral structures shall not be undermined unless a support system or other method of protection is provided.

Protection of the Public

1. Guardrails, fences, or barricades shall be provided on excavations adjacent to walkways, driveways and other pedestrian or vehicle thoroughfares.

2. Warning lights shall be maintained as necessary for the safety of the public at night.

Protection Systems

1. Employees in an excavation shall be protected from cave-ins by using an appropriate sloping, shoring, or shielding system. The only exceptions are:

• Excavations made entirely in stable rock; or
• Excavations less than 5 feet deep where examination by a competent person provides no signs of a potential cave-in.

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

3. Protective systems for excavations under 20 feet shall be designed by a knowledgeable person. Systems shall be inspected daily, prior to work, by a competent person. Protective systems over 20 feet deep must be designed by a registered professional engineer.

Access and Means of Egress

1. Stairs, ladders, ramps or other safe means shall be provided where employees enter trench excavations over 4 feet deep.

2. The maximum distance along the length of the trench to reach the means of egress shall not exceed 25 feet.

3. The sloped end of a trench may be used to enter the trench if employees can walk the ramp in an upright manner. A knotted rope line may not be used to assist employees using sloped areas as access to trenches.

4. Lifting equipment such as backhoes, shall not be used to move employees into and out of the trench.

Structural Ramps

1. Structural ramps used solely by employees for access or egress from excavations shall be designed by a competent person.

2. Structural ramps used for equipment shall be designed by a competent person qualified in structural design.

3. Ramps and runways constructed of two or more structural members shall be connected together to prevent movement. Structural members shall be of uniform thickness. Cleats or other appropriate means used to connect runway structural members shall be attached to the bottom of the runway or shall be attached in a manner to prevent tripping.

4. Structural ramps used for steps shall be provided with cleats or other surface treatments to prevent slipping.

Ladders

1. When portable ladders are used, the ladder side rails shall extend a minimum of 3 feet above the surface of the excavation.

2. Ladders shall have nonconductive side rails if work is performed near exposed energized equipment.

3. Ladders will be inspected before use for signs of damage or defects. Damaged ladders will be removed from service and marked "Do Not Use" until repaired.

4. Ladders shall be used on stable and level surfaces unless secured. Ladders placed where they can be displaced by workplace activities or traffic shall be secured or barricaded to keep activities away from the ladder.

5. Extension ladders shall be positioned so that the foot of the ladder is one-quarter of the working length away from the support. Employees shall not carry any object or load while on the ladder that could cause them to lose their balance.

1. Employees exposed to vehicular traffic (not just directing traffic) shall wear warning vests or other high-visibility garments.

Openings

1. Wells, holes, pits, shafts, and all similar hazardous excavations shall be effectively barricaded or covered and posted as necessary to prevent unauthorized access.

2. All temporary excavations of this type shall be backfilled as soon as possible.

Employee Exposure to Falling Loads

1. Employees shall not work underneath loads handled by lifting or digging equipment.

2. Employees shall stand away from any vehicle being loaded or unloaded.

3. Operators may remain in the cabs of vehicles being loaded or unloaded if the vehicles provide adequate protection.

Warning System for Mobile Equipment

1. A warning system shall be used when mobile equipment is operated near the edge of an excavation if the operator does not have a clear view of the edge.

2. The warning system shall consist of barricades, hand or mechanical signals, or stop logs.

3. A warning system is not required for mobile equipment used to push soil back into the trench.

Hazardous Atmospheres

1. A qualified individual will test the atmosphere in excavations over four feet deep if a hazardous atmosphere is possible. The qualified individual will be trained by the Safety Office. A hazardous atmosphere may exist, for example, in excavations in landfill areas, where hazardous substances are stored, or near gas pipelines.

2. Adequate precautions will be taken to prevent exposures to atmospheres containing less than 19.5 percent oxygen and other hazardous atmospheres. These precautions include proper respiratory protection or forced mechanical ventilation.

3. Forced mechanical ventilation shall be used to prevent exposure to an atmosphere containing a flammable gas in excess of 10 percent of its lower flammability limit.

4. When controls are used to reduce the level of atmospheric contaminants to acceptable limits, continuous air monitoring will be performed. The device used for atmospheric monitoring will be equipped with an audible and visual alarm.

5. Atmospheric testing will be performed using a properly calibrated direct reading gas monitor. Direct reading gas detector tubes or other acceptable means may also be used to test potentially toxic atmospheres.

6. Atmospheric testing instruments shall be calibrated at least every six months by the Safety Office.

7. Each atmospheric testing instrument will be field checked immediately before use to ensure that it is operating properly.

8. Emergency rescue equipment such as breathing apparatus, safety harness and line, and a tripod shall be readily available where hazardous atmospheres may develop in an excavation. Only personnel that have approved training and appropriate equipment shall attempt retrieval into a hazardous atmosphere.

9. If entry into a known hazardous atmosphere must be performed, the Safety Office shall be given advanced notice so hazards can be evaluated and rescue personnel placed on standby.

Personal Protective Equipment

1. All employees working in trenches or excavations shall wear approved hardhats and steel toed shoes.

2. Employees exposed to flying fragments, dust, or other similar materials shall wear approved safety glasses with side shields.

3. Employees exposed to hazards produced by welding, cutting or brazing operations shall use approved spectacles, faceshield, or helmet.

4. Employees entering bell-bottom pier holes or other similar deep and confined footing excavations shall wear a harness with a lifeline attached to it. The lifeline shall be separate from any line used to handle materials and be individually attended at all times while the employee is in the excavation.

5. As necessary, employees shall wear appropriate gloves for hand protection.

6. Employees using or working near, hammer drills, masonry saws, jackhammers or similar high noise producing equipment shall use suitable hearing protection.

1. Walkways shall be provided where employees or equipment are permitted to cross over excavations. Approved guardrails shall be provided where walkways are six feet or more above lower levels.

1. Employees will not work in excavations that contain water unless precautions have been taken to protect them from hazards posed by water accumulation. The precautions taken could include special support or shield systems to protect from cave-ins, water removal, or use of safety harnesses and lifelines.

2. If water is controlled with water removal equipment, the equipment shall be monitored by a competent person to ensure proper operation.

3. If excavation work interrupts the natural drainage of surface water (such as streams), diversion ditches, dikes, or other suitable means shall be used to prevent surface water from entering the excavation. Precautions shall also be taken to provide adequate drainage in the area adjacent to the excavation. Excavations subject to runoff from heavy rains shall be inspected by a competent person to determine if precautions should be taken.

1. Adequate protection shall be provided to protect employees from loose rock or soil that could fall from an excavation face. Such protection shall consist of:

• Scaling to remove lose material.
• Installation of protective barricades, such as wire mesh or timber, at appropriate intervals on the face of the slope to stop and contain falling materials.
• Other means that provide equivalent protection.

2. Employees shall be protected from materials that could fall into excavations. Protection shall be provided by keeping materials at least two feet from the edge of excavations or by restraining devices.

3. Employees shall not work above other employees on the faces of sloped or benched systems unless employees at the lower levels are protected from the hazard of falling material or equipment.

1. A 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. The inspection shall be conducted before the start of work and as needed through the shift. Inspections shall also be made after every rainstorm or other occurrence that may increase hazards.

2. Where the competent person finds evidence that could result in a possible cave-in, failure of protective systems, hazardous atmosphere, or other hazardous conditions, exposed employees will be removed from the hazardous area until precautions have been taken to assure their safety.

3. A written log of all inspections will be maintained by the competent person. The log shall include the date, work site location, results of the inspection, and corrective actions.

6.0  REQUIREMENTS FOR PROTECTIVE SYSTEMS

Sloping and Benching Systems

1. The slope and configuration of sloping and benching systems shall be selected and constructed using one of the following options:

Option 1. All slopes and configurations are designed assuming the most unstable soil conditions (type C soil). Excavations shall be sloped at an angle of one and one-half horizontal to one vertical (34 degrees measured from the horizontal). The slopes used shall be excavated according to the configurations shown for type C soil in Appendix B. Soil analysis is not needed.

Option 2. Slopes and configurations are determined using Appendix A and B of the OSHA regulations. Appendix A is used to classify the soil and appendix B to determine the allowable slope and configuration for the type of soil. Soil classification must be done by a competent person.

Option 3. The design of sloping or benching systems may be constructed according to other tabulated data such as tables and charts. The tabulated data must be in written form and include the following:

• Identification of the factors that affect the selection of a sloping or benching system.
• Identification of the limits of use of the data, including the magnitude and configuration of the slopes determined to be safe.
• Other information needed by the user to make correct selection of a protective system.
• One copy of the tabulated data that identifies the registered professional engineer who approved the data shall be maintained at the jobsite during construction of the protective system.

Option 4. Sloping and benching systems not utilizing one of the above options shall be approved by a registered professional engineer. Designs shall be in written form and include at least the following:

• The magnitude and configurations of the slopes determined to be safe.
• The identity of the registered professional engineer approving the design.
• At least one copy of the design shall be maintained at the jobsite while the slope is being constructed.

Shoring, Shielding and Other Protective Systems

1. The design of shoring systems, shield systems, and other protective systems shall be constructed according to one of the following options:

Option 1. Systems may be designed using appendices A, C, and D of the OSHA regulations. Design of timber shoring in trenches shall be made according to appendix A and C. Appendix A is used to analyze the soil type and appendix C to select the proper timber shoring configuration. Design of aluminum hydraulic shoring in trenches not exceeding 20 feet shall be in accordance with option 2, but if manufacturers' tabulated data cannot be used, then designs shall conform with appendix D.

Option 2. Protective systems may be designed using tabulated data from the manufacturer. This option allows the use of manufactured protective systems such as metal hydraulic shoring or shields. Protective systems designed by this option shall be constructed and used according to the specifications and requirements of the manufacturer. Deviation from these requirements is allowed if written approval is obtained from the manufacturer. This approval must be kept at the jobsite during construction of the protective system.

Option 3. Systems may be designed using other tabulated data if the data has been approved by a registered professional engineer. The tabulated data shall be in written form and include the following:

• Identification of the factors that affect the selection of a protective system drawn from such data.
• Identification of the limits of use of the data.
• Information needed by the user to make a correct selection of a protective system from the data.
• At least one copy of the tabulated data, identifying the registered professional engineer who approved the data, shall be maintained at the jobsite during construction of the protective system.

Option 4. Protective systems can be designed by a registered professional engineer. Designs shall be in written form and include a plan indicating the sizes, types, and configurations of the materials used and the identity of the registered professional engineer. At least one copy of the design shall be maintained at the jobsite during construction of the protective system.

Materials and Equipment

1. Materials and equipment used for protective systems shall be free from damage or defects that might affect their function.

2. Manufactured materials and equipment used for protective systems shall be used and maintained according to recommendations of the manufacturer, and in a manner that will prevent employee exposure to hazards.

3. When material or equipment used for protective systems are damaged, these systems must be examined by a competent person to evaluate its suitability for continued use. If the competent person cannot assure the safe use of the system, then the material or equipment shall be removed from service and evaluated by a registered professional engineer.

Installation and Removal of Support

1. Members of support systems shall be securely connected to prevent sliding, falling, kickout, or other failure.

2. Support systems shall be installed and removed in a way that protects employees from cave-ins, structural collapses, or from being struck by members of the support system.

3. Individual members of support systems shall not be subjected to excessive loads.

4. Before temporary removal of individual support members begins, additional precautions shall be taken to ensure the safety of employees. These precautions could include the installation of other structural members to carry the loads imposed on the support system.

5. Removal of support systems shall begin at the bottom of the excavation. Members shall be released slowly. If there is any indication of possible failure of the remaining structure or possible cave-in the work shall be halted until it can be examined.

6. Backfilling shall progress with the removal of support systems from excavations.

7. The following additional requirements for support systems are specific for trench excavations:

• Excavation of material to a level not more than two feet below the bottom of a support system is allowed, but only if the system is designed to resist the forces calculated for the full depth of the trench. There shall be no indications while the trench is open of a possible loss of soil from behind or below the bottom of the support system.
• Installation of a support system shall be closely coordinated with the excavation of trenches.

Shield Systems

1. Shield systems shall not be subjected to loads greater than their design capacity.

2. Shields shall be installed to restrict lateral or other hazardous movement of the shield that could occur during cave-in or unexpected soil movement.

3. Employees shall be protected from cave-ins when entering or exiting the shield.

4. Employees shall not be allowed in shields when shields are being installed, removed, or moved vertically.

5. Additional requirements for shields used in trenches:

• Excavation of material to a level no greater than 2 feet below the bottom of the shield system is allowed, but only if the system is designed to resist the forces calculated for the full depth of the trench. There shall be no indications while the trench is open of a possible loss of soil from behind or below the bottom of the shield system.

Appendix A: Soil Classification

Appendix A describes a method of classifying soil and rock deposits based on site and environmental conditions, and on the structure and composition of the earth deposits. The appendix contains definitions, requirements, and describes acceptable visual and manual tests for use in classifying soils.

This appendix applies when a sloping or benching system is designed as a method of protection for employees from cave-ins. This appendix also applies when timber shoring is designed according to appendix C and aluminum hydraulic shoring is designed according to appendix D. Appendix A also applies if other protective systems are designed from data requiring that soil be classified.

Each soil and rock deposit must be classified by a competent person as stable rock, type A, type B, or type C soil. Type A soil is the strongest (e.g., clay) and Type C soil is the weakest and most unstable (e.g., sand). Classification is based on at least one visual and one manual analysis. Analysis may be done using the methods described in this appendix or any other recognized method of soil classification and testing such as those adopted by the American Society for Testing Materials.

Once the soil type has been determined the proper protective system can be selected. Each layer in a layered system must be classified. The protective system for the weakest layer must be chosen. Soils may have to be reclassified in case of a heavy rainstorm or other hazard-increasing occurrence.

Appendix B: Sloping and Benching

This appendix is mandatory if the employer decides to classify the soil and chooses a sloping or benching system. The slopes in the appendix are the maximum allowable slopes for each type of soil, i.e., the steepest incline allowed for the particular soil. Slopes are expressed as a ratio of horizontal distance to vertical rise. In Type C soil, for example, a trench 10 feet deep would require a horizontal distance of 15 feet on both sides of the trench (1 1/2:1). The only exception to the maximum allowable slopes is for short-term (less than 24 hours) excavations in Type A soil where the excavation is 12 feet or less in depth. The slope for such an excavation can be 1/2:1 rather than 3/4:1.

Following are the maximum allowable slopes for excavations less than 20 feet deep:

Soil Type         Slope

Stable rock        vertical

Type A               3/4:1

Type B               1:1

Type C             1 1/2:1

Appendix C: Timber Shoring

This appendix is mandatory when an employer uses timber shoring in a trench 20 feet or less in depth. The employer must first classify the soil using Appendix A, then select the proper configuration from the tables in appendix C.

Appendix D: Aluminum Hydraulic Shoring for Trenches

This appendix is mandatory when an employer uses aluminum hydraulic shoring in a trench 20 feet or less in depth. This option is only used when the employer cannot utilize manufacturers' tabulated data. The employer must first classify the soil using Appendix A, then select the proper configuration from the tables in this appendix.