T.R. Consulting, Inc.
This month, our monthly safety article focuses on some of the more basic requirements for compliance with regulations on excavations. The first part of the article is a summary general requirements, the second part is a table explaining proper sloping of excavation walls and the third part is a bullet outline of excavation requirements.
PLANNING YOUR EXCAVATION
The estimated location of utility installations, such as sewer, telephone, fuel, electric, water lines, or any other underground installations that reasonably may be expected to be encountered during excavation work, needs to be determined prior to opening an excavation. When utility companies or owners cannot respond to a request to locate underground utility installations within 24 hours (unless a longer period is required by state or local law), or cannot establish the exact location of these installations, the employer is allowed to proceed, so long as the employer does so with caution, and so long as detection equipment or other acceptable means to locate utility installations are used.
When excavation operations approach the estimated location of underground installations, the exact location of the installations needs to be determined by safe and acceptable means. Since most utility companies provide markings that are supposed to be accurate to within about two feet, hand excavation of the soil beginning just outside the marked zone can be used to confirm the exact location of the underground structure to assure that excavating equipment will not damage it and allow the equipment to excavate nearer to the underground structure.
EMPLOYEE ACCESS TO EXCAVATIONS
A stairway, ladder, ramp or other safe means of egress must be located in excavations that are 4 feet or more in depth so as to require no more than 25 feet of lateral travel for employees to reach a means of egress. In the case of a trench, egress points must be placed no more than 25 feet apart for the entire length of the trench. If an area of the trench is to be unoccupied, placing physical barriers around the area that will not be occupied can eliminate the requirement for placing means of egress within those areas of the trench.
HEAVY EQUIPMENT OPERATION
When mobile equipment is operated adjacent to an excavation, or when such equipment is required to approach the edge of an excavation, the operator must either have a clear and direct view of the edge of the excavation, or a warning system needs to be utilized. Examples of warning systems include: barricades, hand or mechanical signals, or stop logs/curbs. Where possible, the grade should be away from the excavation.
MONITORING OF EXCAVATIONS
Where oxygen deficiency (atmospheres containing less than 19.5 percent oxygen) or a hazardous atmosphere exists or could reasonably be expected to exist (OSHA does not differentiate between evaluation of real versus potential risks), such as in excavations in landfill areas or excavations in areas where hazardous substances are stored nearby, the atmospheres in the excavation must be tested before employees enter excavations greater than 4 feet in depth.
WATER IN EXCAVATIONS
Employees are not allowed work in excavations in which there is accumulated water, or in excavations in which water is accumulating, unless adequate precautions have been taken to protect employees against the hazards posed by water accumulation. The precautions necessary to protect employees adequately vary with each situation, but could include special support or shield systems to protect from cave-ins, water removal to control the level of accumulating water, or use of a safety harness and lifeline.
Where the stability of adjoining buildings, walls, or other structures could be endangered by excavation operations, support systems such as shoring, bracing, or underpinning are required to be provided to ensure the stability of such structures.
Employees need to be protected from excavated or other materials or equipment that could pose a hazard by falling or rolling into excavations. This protection can be provided by placing and keeping such materials or equipment at least 2 feet from the edge of excavations, or by the use of retaining devices that are sufficient to prevent materials or equipment from falling or rolling into excavations, or by a combination of both if necessary.
Daily inspections of excavations, the adjacent areas, and protective systems are required to be performed by a competent person. The competent person should look for evidence of a situation that could result in possible cave-ins, indications of failure of protective systems, hazardous atmospheres, or other hazardous conditions. An inspection must be conducted by the competent person prior to the start of work and as needed throughout the shift. Inspections are also required after every rainstorm or other hazard increasing occurrence when employee exposure can be reasonably anticipated (if no one will be occupying the excavation, the inspection is not required).
SLOPING AND SHORING
Excavation edges 5 feet or greater in depth (4 feet in California) are required to either be sloped or shored to prevent collapse when the excavation is to be occupied. It is important to understand that excavated material does not have to cover the nose and mouth to cause suffocation. Excavated materials surrounding the chest can cause a person to be constricted by the weight of the surrounding material. With each exhaled breath, the the volume of air that can be inhaled is reduced until suffocation occurs. Additionally, depending on the activity to be performed within the excavation, sloping or shoring of excavation walls may be necessary at leeser depths. For example, a worker required to kneel within an trench to perform work duties could be adversely affected by the collapse of excavation walls as little as three feet in height.
The following table provides basic information on allowable slope configurations. These slopes can be accomplished with straight slope edges, simple benching and multiple benching configurations. Additional sources for information on excavations is provided in Department of Labor publication OSHA 2226, American Petroleum Institute Recommended Practice API RP1615, and Petroleum Equipment Institute Recommended Practice PEI RP100.
MAXIMUM ALLOWABLE SLOPES
SOIL OR ROCK TYPE | MAXIMUM ALLOWABLE SLOPES (H:V)(1) FOR
| EXCAVATIONS LESS THAN 20 FEET DEEP(3)
STABLE ROCK | VERTICAL (90 Deg.)
TYPE A (2) | 3/4:1 (53 Deg.)
TYPE B | 1:1 (45 Deg.)
TYPE C | 1 1/2:1 (34 Deg.)
Footnote(1) Numbers shown in parentheses next to maximum allowable slopes are angles expressed in degrees from the horizontal. Angles have been rounded off.
Footnote(2) A short-term maximum allowable slope of 1/2H:1V (63 degrees)is allowed in excavations in Type A soil that are 12 feed (3.67 m) or less in depth. Short-term maximum allowable slopes for excavations greater than 12 feet (3.67 m) in depth shall be 3/4H:1V (53 degrees).
Footnote(3) Sloping or benching for excavations greater than 20 feet deep shall be designed by a registered professional engineer.
BULLET OUTLINE SUMMARY
* PRIOR TO INITIALIZATION OF EXCAVATION ACTIVITIES THE ESTIMATED LOCATION OF UTILITY AND OTHER UNDERGROUND INSTALLATIONS WHICH COULD REASONABLY BE ANTICIPATED MUST BE ESTABLISHED
* AS EXCAVATION ACTIVITIES APPROACH THE ESTIMATED LOCATION OF UNDERGROUND INSTALLATIONS, THE EXACT LOCATION IS TO BE DETERMINED
* EMPLOYEES ARE NOT PERMITTED UNDERNEATH LOADS HANDLED BY LIFTING OR DIGGING EQUIPMENT
* EMPLOYEES ARE REQUIRED TO STAND AWAY FROM ANY VEHICLE BEING LOADED OR UNLOADED TO AVOID BEING STRUCK BY ANY SPILLAGE OR FALLING MATERIALS
* EQUIPMENT WHICH MUST OPERATE NEAR OR APPROACH THE EDGE OF THE EXCAVATION, WHERE THE OPERATOR DOES NOT HAVE A CLEAR AND UNOBSTRUCTED VIEW OF THE EXCAVATION EDGE, SHALL BE USED IN CONJUNCTION WITH AN ADEQUATE WARNING DEVICE OR SYSTEM
* EXPOSURE TO ATMOSPHERES GREATER THAN 20% LEL ARE NOT PERMITTED
* EMERGENCY RESCUE EQUIPMENT MUST BE READILY AVAILABLE WHERE HAZARDOUS ATMOSPHERIC CONDITIONS EXIST OR COULD REASONABLY EXIST
* EMPLOYEES MUST NOT WORK IN EXCAVATIONS WHICH CONTAIN ACCUMULATED WATER OR WHICH ARE ACCUMULATING WATER WITHOUT ADEQUATE SAFE GUARDS
* STABILITY OF ADJACENT STRUCTURES POTENTIALLY AFFECTED BY EXCAVATION OPERATIONS MUST BE DETERMINED
EXCAVATIONS 4 FEET DEEP OR GREATER:
* MUST BE EVALUATED BY A QUALIFIED PERSON WHEN A HAZARDOUS ATMOSPHERE EXISTS OR COULD REASONABLY EXIST PRIOR TO ALLOWING ENTRY INTO THAT EXCAVATION
* MUST HAVE STAIRWAYS, LADDERS, RAMPS OR OTHER SAFE MEANS OF EGRESS LOCATED SO THAT EMPLOYEES WOULD REQUIRE NO MORE THAN 25 FEET OF LATERAL TRAVEL TO REACH THE NEAREST MEANS OF EGRESS
EXCAVATIONS 5 FEET OR GREATER (4 FEET IN CALIFORNIA) IN DEPTH:
* MUST BE SLOPED OR SHORED TO PREVENT THE EXCAVATION WALLS FROM COLLAPSING ON INDIVIDUALS WORKING IN THE EXCAVATION
To return to the T.R. Consulting safety home page go to: http://www.trconsultinggroup.com/safety/index.html
To go to the training pages go to:
To go to the safety directory page go to