RIESGOS EN EXCAVACIONES 1926 Subpart P ‑ Excavations This presentation is designed to assist trainers conducting OSHA 10-hour Construction Industry outreach training for workers. Since workers are the target audience, this presentation emphasizes hazard identification, avoidance, and control – not standards. No attempt has been made to treat the topic exhaustively. It is essential that trainers tailor their presentations to the needs and understanding of their audience. This presentation is not a substitute for any of the provisions of the Occupational Safety and Health Act of 1970 or for any standards issued by the U.S. Department of Labor. Mention of trade names, commercial products, or organizations does not imply endorsement by the U.S. Department of Labor.

Peligros Gran rieso de rotura del talud Otros riesgos: Asfixia Inhalación de materiales tóxicos Fuego Colapso por maquinaria cercana Accidentes por servicios afectados Instructor note: OSHA Standard Exemptions: House foundation/basement excavations (including those that become trenches by definition when formwork, foundations, or walls are constructed) are exempt from the OSHA standard. The specific information regarding the interpretation of this exemption may be found on the OSHA public web site. Reference 29 CFR 1926.652. The exemption specifies height and width for the excavation, impact of water and environmental conditions, soil and equipment factors, and operation of heavy equipment in the vicinity.

Resultado de heridas o muerte Operación muy peligrosa Muchos accidentes en zanjas de entre 2 y 6 m Muchas veces no se toman protecciones

Definiciones Excavacion – general. Zanja – pequeña excavación de no más de 5 m de ancho. Entibación – sistema de protección de trabajadores Talud – pendiente de la pared de la excavación. Reference 1926.650 Shield (shield system) -- a structure able to withstand a cave-in and protect employees with the structure. Shields can be permanent structure or can be designed to be portable and moved along as work progresses. Also known as trench box or trench shield. Shoring (shoring system) -- a structure such as a metal hydraulic, mechanical or timber shoring system that supports the sides of an excavation and which is designed to prevent cave-ins. Sloping (sloping system) -- protects employees from cave-ins by excavating to form sides of an excavation that are inclined away from the excavation to prevent cave-ins. The angle of incline varies with differences in such factors as the soil type, environmental conditions of exposure, and application of surcharge loads.

Sistemas de protección Diseño adecuado del talud Diseño correcto de la entibación más correcto manejo de materiales y equipos sistema de construcción adecuado Resultado protección de empleados y obras Several factors come into play when developing a total “protective system”. The design of of the system itself, how materials and equipment are handled in and around the excavation, and installation and removal of protective system components.

Generalidades Las excavaciones de zanjas se ejecutarán con una inclinación de talud provisional adecuadas a las características del terreno, debiéndose considerar peligrosa toda excavación cuya pendiente sea superior a su talud natural

Generalidades Si se emplearan taludes más acentuados que el adecuado a las características del terreno, o bien se lleven a cabo mediante bermas que no reúnan las condiciones indicadas, se dispondrá una entibación que por su forma, materiales empleados y secciones de éstos ofrezcan absoluta seguridad, de acuerdo a las características del terreno: entibación cuajada, semicuajada o ligera. La entibación debe ser dimensionada para las cargas máximas previsibles en las condiciones más desfavorables

Taludes

Taludes

Entibaciones

Peligro Mala colocación de puntales y accesos Reference 1926.652(a) and 1926.652(c)(1) Designs for aluminum hydraulic shoring shall be in accordance with paragraph (c)(2), but if manufacturer's tabulated data cannot be utilized, designs shall be in accordance with appendix D. Employees exposed to potential cave-ins must be protected by sloping or benching the sides of the excavation, by supporting the sides of the excavation, or by placing a shield between the side of the excavation and the work area. 1926 Subpart P Appendix D Aluminum Hydraulic Shoring for Trenches Contains information that can be used when aluminum hydraulic shoring is provided as a method of protection against cave-ins in trenches that are not more than 20 feet deep.

Peligros Reference 1926.652(a) and (b) and (c)

Otros peligros Agua Falta de oxígeno Humos tóxicos Accesos Caídas Equipos

El agua Muy peligrosa porque inestabiliza la excavación 1926.651(h) Employees shall not 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. If water is controlled or prevented from accumulating by the use of water removal equipment, the water removal equipment and operations shall be monitored by a competent person to ensure proper operation. 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 and to provide adequate drainage of the area adjacent to the excavation.

Atmósfera tóxica Poco oxígeno Gases Otras sustancias Must also test where oxygen deficiency or a hazardous atmosphere could reasonably be expected to exist, before an employee enters the excavation. If hazardous conditions exist, controls such as proper respiratory protection or ventilation must be provided. Also, controls used to reduce atmospheric contaminants to acceptable levels must be tested regularly. Where adverse atmospheric conditions may exist or develop in an excavation, the employer also must provide and ensure that emergency rescue equipment, (e.g., breathing apparatus, a safety harness and line, basket stretcher, etc.) is readily available. This equipment must be attended when used. Employees shall not be permitted to work in hazardous and/or toxic atmospheres. Such atmospheres include those with: -- less than 19.5% oxygen, -- a combustible gas concentration greater than 20% of the lower flammable limit, and, -- concentrations of hazardous substance that exceed those specified in the Threshold Limit Values for airborne contaminants established by the ACGIH.

Accesos Debe ser más alta que la excavación Reference 1926.651(c(1) Structural ramps - Structural ramps that are used solely by employees as a means of access or egress from excavations shall be designed by a competent person. Structural ramps used for access or egress of equipment shall be designed by a competent person qualified in structural design, and shall be constructed in accordance with the design. - Ramps and runways constructed of two or more structural members shall have the structural members connected together to prevent displacement. - Structural members used for ramps and runways 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. - Structural ramps used in lieu of steps shall be provided with cleats or other surface treatments o the top surface to prevent slipping. Debe ser más alta que la excavación