Trenching and excavations are very dangerous operations in the workplace. The greatest hazard associated with trench work is a trench cave-in. Cave-in accidents have twice as many fatalities in comparison to all other construction accidents. Employers and employees have to develop a detailed plan of operation, perform a hazard analysis, inspect the job site, and remain safety conscious at all times. Identifying and understanding the many hazards present in trenching operations can prevent tragedies on a job site. The following list comprises many trench hazards that have to be evaluated, mitigated, and abated before trench-work begins. Location of underground utilities - Contractors must make an effort to notify utility owners of proposed trench work near or around the location of suspected utilities or before new trenching projects begin. o Ask owners for exact locations o Inquire of any and all hazards created by the utilities o Are there ways to abate or control the hazards associated with those utilities o If contact with utility owners cannot be made within 24 hours, proceed cautiously with trench operation Inclement weather - Always obtain weather reports on a daily basis before starting any trench operations. Severe weather can have serious effects on the stability of a trench and create deadly hazards within a matter of minutes. o Alert employees of impending storms, heavy rains, potential flooding, freezes/thaws and lightning Soil types - Making a determination on soil type will identify specific hazards and will dictate trench protection systems and regulations. o Soil testing should always be conducted by a competent person trained in classifying soils o Always attempt to use multiple forms of testing Visual Tests-identify features and characteristics of the soil. If present, identify sand, gravel, silts, clays, solid rock, etc. Look for fissures or cracks in soil Identify standing or seeping water in soil Take note of any evidence of erosion Evidence that the location has been excavated before Manual Tests-employ a competent person to complete manual testing via various means and instrumentation. Vibrations - There are many sources of vibrations on job sites, all of which can have a great effect on the shifting or stability of trenches. Here is a list of some common sources: o Construction machinery o Highway traffic o Railroad traffic o Pile driving operations o Jack hammering operations o Grinding and paving operations o Industrial operations Water - Standing and flowing water can create immediate cave-in and drowning hazards. o Pump out any and all standing water inside of trench o Divert flowing water away from trenches o Assess adjacent structures to identify where runoff will be deposited o Evacuate any trenches where water is seeping through the soil Adjacent structures and over-head operations o Assess whether or not the weight of adjacent structures will effect the stability of the trench o Wear appropriate PPE and construct over-head protection for employees who may be injured by falling objects o Determine if excavating operations will effect the stability of adjacent structures Defects in protective systems - Always inspect safety equipment before utilizing. o Look for inadequate or weakened welds on trench boxes o Pneumatic lines should be assessed for air leaks and broken couplings. Pneumatic trench jacks with leaks should never be used o Always use to manufacturers specifications on the equipment o Never exceed posted load and weight limits on equipment Inexperienced employees - Anytime an employer feels that an employee is unaware of job responsibilities and company safety policies, that employee is not allowed to work in trenching operations until training has been conducted and the employer feels the employee has become competent. All of the previous hazards should be identified and assessed before any trench operation begins.
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