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TRENCHING AND EXCAVATIONS. Tool Box Session. INTRODUCTION.
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TRENCHING AND EXCAVATIONS Tool Box Session GA Tech Safety and Health Consultation Program
INTRODUCTION This training information has been prepared by the Safety and Health Consultation Program at Georgia Tech with the technical collaboration of Mr. Juán C. Rodriguez and under the sponsorship of OSHA. Its content may be copied and distributed for free, and the only request made to the user is that Georgia Tech’s Safety and Health Consultation Program be acknowledged as the source. All information contained in this training is believed to be correct by the authors, but it is important to point out that, this is not an official OSHA publication and has not been revised or approved by OSHA. The user should be aware that the recommendations provided in this training do not replace any OSHA standard or regulation. Georgia Tech Safety and Health Consultation Program Georgia Tech Research Institute 260 14th Street, Fourth Floor Atlanta, GA 30332-0837 Voice : (404) 407-7431 FAX : (404) 407-8275 Web http//www.oshainfo.gatech.edu Email: art.wickman@gtri.gatech.edu GA Tech Safety and Health Consultation Program
Definitions • Cave-in: means the separation of a mass of soil or rock material from the side of an excavation, or the loss of soil from under a trench shield or support system. During a cave-in this material moves suddenly into the excavation, either by falling or sliding, in sufficient quantity to entrap, bury, or otherwise injure and immobilize a person GA Tech Safety and Health Consultation Program
Definitions • Competent person: means a person who is capable of identifying existing and predictable hazards in an excavation, or in the work practices of employees. If conditions are unsanitary, hazardous, or dangerous, the competent person has the authority to take prompt corrective measures to eliminate the hazards GA Tech Safety and Health Consultation Program
Definitions • Excavation: means any man-made cut, cavity, trench, or depression in an earth surface, formed by earth removal • Trench: means a long and narrow excavation made below the surface of the ground. In general, the depth of a trench is greater than the width GA Tech Safety and Health Consultation Program
Definitions • Stable Rock: means natural solid mineral material • Soil Types • Type A: means cohesive soils; example: clay • Type B: means soil with poor cohesion, example: crushed rock / angular gravel/sandy soil • Type C: means soil without cohesiveness, example: gravel and sand GA Tech Safety and Health Consultation Program
Acceptable visual and manual tests for soil classification • Observe the area adjacent to the excavation and the sides of the opened excavation for evidence of surface water, water seeping, utility pipes, or any other underground material such as tree roots • Determine if the soil is cohesive or not • Make use of a pocket penetrometer, thumb penetration, plasticity tests, soil’s hardness property, and any other strength test GA Tech Safety and Health Consultation Program
Maximum allowable slope of an excavation vertical face Slope requirements for excavations < 20 feet deep: • Stable Rock …. Vertical (90o) • Type A……….. 3/4 : 1 (53o) • Type B……….. 1 : 1 (45o) • Type C……… 1 ½ : 1 (34o) GA Tech Safety and Health Consultation Program
Protective Metallic Trench Box • The intended use of a metal trench box is to protect the workers from a cave-in or a similar incident • The designed purpose of timber shoring configurations and other systems of support are to keep the trench’s sides stable • The space between the excavation and the trench box must be as narrow as possible in order to avoid lateral movement of the trench box GA Tech Safety and Health Consultation Program
The soil from the excavation • Soil and any other excavated material shall be placed and kept at least 2 feet from the edge of excavations. • This is done to protect employees from materials (soil, loose rocks) or equipment that could pose a hazard by falling or rolling into the excavation, and also to keep an accurate measurement of the depth of an excavation GA Tech Safety and Health Consultation Program
Access • Trenches more than 4 feet deep must have a ladder or other means of of access • The separation distance between ladders placed in an excavation must not be more than 25 feet • Ladders shall be secured and the upper ends of their side rails must extend at least 36 inches above the surface of the ground / edge of an excavation GA Tech Safety and Health Consultation Program
Location of Underground Utilities • Keep in mind that there might be underground utility installations to be encountered during excavation work, such as sewer, telephone, fuel, electric, water lines, or any other underground installations. • In order to avoid damaging utility lines and as a personal safety measure, the estimated location of such lines must be determined prior to opening an excavation. • “Call Before You Dig” State Laws GA Tech Safety and Health Consultation Program
