trenching and excavation 21.0 - Arkansas Tech University [PDF]

HEALTH AND SAFETY MANUAL. 3. Trench/ shield box. 4. Sloping. 5. Hydraulic shoring. 6. Trench. 7. Registered Professional

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ARKANSAS TECH UNIVERSITY FACILITIES MANAGMENT HEALTH AND SAFETY MANUAL

TRENCHING AND EXCAVATION 21.0 The purpose of the Trenching and Excavation Policy is to help ensure that trenching and excavation operations are performed in a safe manner and in accordance with Excavation Standard Subpart P, 29 CFR 1926.650 and industry best practices. This policy applies to all Facilities Management Group employees who are involved in trenching and excavation operations, as well as, all contractors who may be involved in trenching and excavation operations on the Arkansas Tech University campus. This program shall apply to all open excavations made in the earth’s surface. Excavations include trenches except for those trenches created by the tillage of fields.

21.1 A.

ASSIGNMENT OF RESPONSIBILITIES

It shall be the responsibility of all employees involved in trenching and excavation operations to be familiar with and abide by the provisions of this policy and any other standards or regulations pertinent to safe trenching and excavation operations. The Occupational Safety Coordinator shall be notified before ANY trenching or excavating work is to be performed.

21.2 A.

COMPETENT PERSON TRAINING

A trenching/excavation competent person is defined as an employee who is capable of identifying existing and predictable hazards in the surroundings, or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has the authority to take prompt corrective measures to eliminate those conditions.

B. The competent person for trenching and excavation work must have met these requirements: 1. have attended a REM approved excavation safety course 2. received a certificate and/or card indicating successful completion of the course

C. The competent person for trenching and excavation work must be trained in and knowledgeable in the following areas: 1. Support systems 2. Excavation Page 1 of 8 TRENCHING & EXCAVATION

ARKANSAS TECH UNIVERSITY FACILITIES MANAGMENT HEALTH AND SAFETY MANUAL 3. Trench/ shield box 4. Sloping 5. Hydraulic shoring 6. Trench 7. Registered Professional Engineer (RPE) 8. Failure 9. Uprights 10. Protective systems

D. Additional information that the competent person is required to know: 1. How to document the trench/excavation using the Daily Trench/Excavation Inspection Form. 2. How to identify causes of trench cave-ins i.e. inadequate support systems, inadequate sloping, surcharge loading, etc. 3. Be knowledgeable in the use of manufactures tabulated data. A competent person must be able to identify proper installation techniques and limitations of hydraulic shoring. 4. Be able to identify when end plates on a trench shield are required, how to safely stack shield sections, access and egress requirements, material handling requirements (tag lines, sling safety, etc.) shield construction requirements, and lateral support requirements (REFER TO APPENDIX J-1: EXCAVATION COMPETENT PERSON EVALUATION FORM)

21.3 A.

COMPETENT PERSON DUTIES

The following are duties of the competent person: 1. Maintain a copy of this policy and have a comprehensive knowledge of both. In addition, the competent person(s) must have a general knowledge of all applicable safety standards. 2. Conduct pre-job site review to develop a written job safety analysis that will ensure a safe and efficient job process. A competent person will evaluate all sloping and/or shoring prior to commencing the work. 3. Perform inspections of equipment and trench conditions at the start of each shift and periodically during the shift or as needed by changing conditions. 4. The competent person has the duty and responsibility to remove all employees from hazardous conditions and effect all changes necessary to ensure employee safety. Page 2 of 8 TRENCHING & EXCAVATION

ARKANSAS TECH UNIVERSITY FACILITIES MANAGMENT HEALTH AND SAFETY MANUAL 5. Maintain on-site records of protection systems and inspection reports. 6. If mechanical protection is used, the competent person will oversee the installation of such system. 7. Verify that ramps and walkways for employee use are constructed in compliance with industry best practices. 8. Hold safety meetings with all crew members prior to trenching/excavation operations beginning and during operations as needed. 9. A competent person must be on-site at all times during trenching or excavation operations. 10. Assure that appropriate emergency rescue is available to meet existing or potential conditions. 11. Monitor use of water removal equipment. 12. Ensure that the air quality in the trench or excavation is safe and free of flammable, combustible, or toxic gases ensuring the air is neither oxygen deficient or enriched. 13. The competent person must consult with a Registered Professional Engineer (RPE) if the trench or excavation is over 20’ deep. Specifically with regards to designed shoring, bracing or when the excavation could endanger a nearby structure. This consultation must include written instructions or opinions from the RPE. 14. The competent person must maintain the Daily Trench/Excavation Inspection Form at the work-site and it must be readily available for review by a supervisor or the Occupational Safety Coordinator.

21.4

SOIL CLASSIFICATIONS

All soil on the Arkansas Tech University campus has been classified as Class “C” and all precautions, i.e. shoring, benching, sloping, employee walkways, etc. will be deigned accordingly. By definition, a Class “C” soil is listed as granular soils, including gravel, sand, and loamy sand, or cohesive soils with unconfined compressive strength less than 0.5 tsf (48 kPa) or any submerged rock that is not stable, or freely seeping soil or adversely bedded soils. The requirements for this soil are for any material in a sloped, layered system where the layers dip into the excavation of a slope, must have a slope of four horizontal to one vertical (4H:1V) or steeper. The maximum allowable slope for Class “C” soil is 1 ½:1 (34º). SEE FIGURES BELOW:

Page 3 of 8 TRENCHING & EXCAVATION

ARKANSAS TECH UNIVERSITY FACILITIES MANAGMENT HEALTH AND SAFETY MANUAL A.

EXCAVATIONS MADE IN CLASS “C” SOIL

1. All simple slope excavations 20 feet or less in depth shall have a maximum allowable slope of 1½:1.

SIMPLE SLOPE 2. All excavations 20 feet or less in depth which have vertically sided lower portions shall be shielded or supported to a height at least 18 inches above the top of the vertical side. All such excavations shall have a maximum allowable slope of 1½:1. Vertical sided lower portion Page 4 of 8 TRENCHING & EXCAVATION

ARKANSAS TECH UNIVERSITY FACILITIES MANAGMENT HEALTH AND SAFETY MANUAL 21.5 A.

STAGING AND SURFACE ENCUMBRANCES

When leaving an excavation open and unattended the following measures shall be taken to prevent unauthorized access: 1. When an excavation is unattended and in excess of one (1) foot in depth a six (6) foot chain link fence is required surrounding the excavation. 2. When an excavation is less than a foot in depth, 42 inch temporary fencing is acceptable. 3. Fencing is required for depressions left by the removal of trees unless the depression is backfilled at once. 4. Any surface encumbrances, or impediments, that are located in a position that could create a hazard to employees in or around the excavation shall be removed or supported to safeguard employees. 5. All soil and rock removed during the excavation shall be placed at least two (2) feet from the edge of the excavation.

21.6

UTILITY LOCATING

It is expected that all utilities in the vicinity of the excavation will be marked or located prior to the disturbance of soil or ground cover. If excavation operations approach the estimated location of underground installations, clearance must be maintained between the underground utility, as marked, and the cutting edge or point of mechanized equipment. Any utilities exposed during excavation activities shall be properly supported to prevent movement of the utility line.

21.7

ACCESS AND EGRESS TO THE TRENCH

A stairway, ladder, ramp, or other safe means of egress shall be located in trench excavations that are four (4) feet in depth or greater. Safe means of egress should be provided so that no more than 25 feet of lateral travel is necessary for employees to reach the egress. If a ladder is used for access or egress it must be secure and extend at least 36 inches above the landing.

Page 5 of 8 TRENCHING & EXCAVATION

ARKANSAS TECH UNIVERSITY FACILITIES MANAGMENT HEALTH AND SAFETY MANUAL 21.8 A.

HAZARDOUS ATMOSHPERES

When potential or existing oxygen deficient or hazardous atmospheres exist, atmospheric monitoring should be performed using authorized and certified air monitoring devices. Atmospheric monitoring should be performed prior to employee entry and continuously during employee entry into an excavation with a potential for an oxygen deficient or hazardous atmosphere. Safe entry conditions are defined as the following: 1. an oxygen content between 19.5-23.5% 2. a lower explosive limit < 10% 3. carbon monoxide < 25 parts per million (ppm) 4. hydrogen sulfide < 1 ppm If an oxygen deficient or hazardous atmosphere exists, measures shall be taken to prevent employee exposure. Where hazardous atmospheric conditions exist or may reasonably be expected to develop during work in during excavation activities the Local Fire Department rescue force MUST be notified.

21.9

HAZARDS FROM WATER ACCUMULATION

University employees shall not work in excavations in which there is accumulated or accumulating water unless appropriate precautions have been taken to protect employees from hazards presented by water. If water removal equipment is utilized to control accumulating water it should be monitored by a competent person. If excavation work interrupts the natural drainage of surface water, diversion ditches, dikes, or other suitable means shall be used to prevent surface water from entering the excavation and to provide adequate drainage of the area adjacent to the excavation.

Page 6 of 8 TRENCHING & EXCAVATION

ARKANSAS TECH UNIVERSITY FACILITIES MANAGMENT HEALTH AND SAFETY MANUAL 21.10 A.

PROTECTION OF EMPLOYEES IN EXCAVATIONS

The following guidelines must be met to ensure protection of the employees working in trenches during excavations: 1. All earthen materials and equipment shall be kept at least two (2) feet from the edge of an excavation to prevent materials or equipment from falling or rolling into excavations. 2. Protection shall also be afforded to prevent loose rock or soil from falling and rolling from an excavation face onto an employee. 3. Employees are not permitted to work on the faces of sloped or benched excavations at levels above other employees except when employees at lower levels are protected from the hazard or falling, rolling, or sliding material and equipment.

21.11

USE OF SUPPORT, SHIELD, AND OTHER PROTECTIVE SYSTEMS

A.

TYPES OF PROTECTIVE SYSTEMS

Trench boxes and hydraulic shoring shall be used according to the manufacturer’s tabulated data, and shall be in accordance with all specifications, recommendations and limitations issued or made by the manufacturer. When a shield (trench box) is used, work shall not be permitted outside the shield. If it necessary to use timber shoring, it shall be used according to tabulated data. Timber shoring in a trench greater than 20 feet in depth shall be designed by a registered professional engineer. A Shield system shall be installed in a manner that will restrict lateral or other hazardous movement and shall not be subject to loads exceeding its capability. Employees shall be protected from the hazard of cave-ins when entering or exiting the areas protected by shields. Employees shall not be allowed in shields when they are being installed, removed, or moved vertically.

21.12 A.

INSPECTIONS

A competent person shall perform daily inspections before work begins and as needed throughout the shift. Inspections should include the following: 1. The excavations, the adjacent areas, and the protective systems.

Page 7 of 8 TRENCHING & EXCAVATION

ARKANSAS TECH UNIVERSITY FACILITIES MANAGMENT HEALTH AND SAFETY MANUAL 2. The identification of problems with the excavation that could result in a cave-in or to identify indications of failure with the protective systems. 3. An evaluation of the potential for a hazardous atmosphere to develop. No employee shall enter an excavation prior to inspection by the competent person. Additionally, no employee shall enter an excavation if a hazard is identified until that hazard has been mitigated. (REFER TO APPENDIX J-2: EXCAVATION INSPECTION FORM)

21.13

RECORD KEEPING

All inspection and competent person forms must be turned into the Safety Office and kept on file for a period of one year.

Page 8 of 8 TRENCHING & EXCAVATION

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