Excavation and Trench Safety

Transcription

1 Ardaman & Associates, Inc. A Tetra Tech Company Newsletter August 5, 2016 Excavation and Trench Safety When a trench or other excavation is made in soil, gravity and residual forces in the ground work to restore the soil to a more stable configuration. If those forces are greater than those holding the trench or excavation walls in place, a cave-in occurs. There are a number of factors which determine the stability of a given excavation wall. It is beyond the scope of this newsletter to fully describe soil mechanics behavior. However, when the soil is sloped or braced appropriately, it will remain safely stable. First, a couple of definitions: Trench (Trench Excavation): A narrow excavation made below the surface of the ground. In general, the depth is greater than the width, but the width of the trench (measured at the bottom) is not greater than 15 feet according to OSHA s definition. Excavation: Any man-made cut, cavity, trench, or depression in an earth surface, formed by earth removal. 1. OSHA requires employers to identify an excavation s hazards and create a safety plan to protect workers. Inside this issue: Excavation Safety Page 1-3 Ardaman Update Page 4,5 Quiz Page 6 The safety plan does not need to be site specific and can be generic. Ardaman has JSAs and a checklist for entering an excavation. (Contact your H&S Coordinator) 2. Safety precautions are required before work begins in an excavation. A competent person (defined by OSHA) inspects the excavation before any workers enter. A competent person is one with the experience to identify hazards and precautions and the authority to take necessary corrective measures. When working on job sites where a general contractor is in charge of site safety, it is the responsibility of the contractor to have a competent person overseeing excavation safety. 3. Most excavations must have systems to protect against cave-ins. Examples of such systems are sloping the sides, benching the sides with steps, installing bracing systems, or using trench boxes. Excavations deeper than 4 feet must be inspected by a competent person. For excavations between 4 and 5 feet in depth, a competent person must decide if a system is needed. For excavations deeper than 5 feet, a protection system must be in place. (The type of protection system chosen depends on soil types and other factors.) 4. Excavation planning requires many other protective measures. Coordinating with utilities to protect workers and underground utility lines. Providing safe ramps. stairways, and/or ladders for workers to use to get in and out of an excavation. Ladders must be placed within 25 feet of the worker, extend 3 feet above the surface and must be secured. Using barricades, stop logs, or other warnings if there is a risk that mobile equipment might reach the edge of the excavation. When required, testing the excavation s atmosphere for contaminants and oxygen when deeper than 4 feet. Where oxygen deficiency or a hazardous atmosphere exists or could reasonably be expected to exist, such as in excavations in landfill areas or excavations in areas where hazardous substances are present nearby, the atmosphere in the excavation should be tested before employees enter excavations greater than 4 feet in depth. Engineering controls can be used such as additional ventilation to ensure there is adequate oxygen in the excavation. When controls are used that are intended to reduce the level of atmospheric contaminants to acceptable levels, testing must be conducted as often as necessary to verify that the atmosphere remains safe. Contact Information: Health & Safety Ardaman & Associates, Inc. Brett A. Buxbaum Orlando, FL P: (407) X 2413 Cell: (407) BBuxbaum@ardaman.com Safety Question: If you have safety concerns about entering an excavation, you should contact the competent person on site. A. True Answer on page 5

2 Page 2 Excavations and Trenching Continued 4. Continued: Excavation planning requires many other protective measures. Protecting against the hazards of water accumulation. Supporting adjoining buildings, walls, pavement, utilities, etc., if needed to ensure their stability. Removing or barricading loose rock or soil to keep it from falling into the excavation. Providing walkways if employees or equipment will cross over excavations. Walkways 6 or more feet above lower levels must have guardrails. 5. Use personal protective equipment to stay safe. When required, assigned respirators for airborne related hazards, harness systems for rescue, high visibility vests, and protective gear (hardhat, safety glasses, safety boots, etc.). 6. Follow Safety Rules and Precautions in and around an excavation. Use ventilation equipment to reduce hazardous concentrations in excavation. Keep excavated material and equipment at least 2 feet from the edge of the hole. Don t work on the face of a sloped or benched excavation when other employees are below unless the employees and slope are fully protected. Remove support systems properly and carefully to prevent cave-ins or other accidents. Use temporary supports while removing permanent supports. Remove supports from the bottom up, backfilling as you go. 7. Follow what to do in an emergency. Leave the excavation or trench promptly and properly if you believe it is dangerous. Don t attempt a rescue unless you are trained, equipped, and authorized to do so. ARDAMAN EXCAVATION POLICY Employees must be alert to the potential for cave-ins when entering an excavation. Trenches must be excavated in accordance with 29 CFR Part Do not enter a trench unless the excavation is protected by a designed system such as shoring, shielding, sloping of the ground or some other equivalent means, except when: a. Excavations are made entirely in stable rock; or b. Excavations are less than 5 feet in depth and examination of the ground by a competent person provides no indication of a potential cave-in. Refer to Excavation Checklist (Forms available from H&S Coordinator) and review with competent person on site. 2. Excavated or other material must be effectively stored and retained at least 2 feet or more from the edge of the excavation. 3. When entering a trench by ladder, be sure it is secured against movement while in use. Since the ladder will rest on a soil base, test its stability before carrying any testing equipment into the excavation. The ladder must have clear access at the top and bottom and be placed at an angle so the horizontal distance from the wall is approximately one quarter the working length of the ladder. The top of the ladder should extend at least 3 feet above the surface of the excavation. 4. Do not jump into an excavation as knees and ankles are easily injured. 5. There should not be more than a 25-foot traveling distance to a ladder from any point within the excavation.

3 Page 3 Excavations and Trenching Continued OSHA SOIL CLASSIFICATION: Excavations and Trenching: 29 CFR 1926 Subpart P Appendix A is based on site and environmental conditions, and on the structure and composition of the soil deposits. The soil classification system means a method of categorizing soil and rock deposits in a hierarchy of Stable Rock, Type A, Type B, and Type C, in decreasing order of stability. Stable rock means: natural solid mineral matter that can be excavated with vertical sides and remain intact while exposed. Type A means: Stiff to hard cohesive soils with an unconfined, compressive strength of 1.5 ton per square foot (tsf) (144 kpa) or greater. Examples of cohesive soils are: clay, silt clay, sandy clay, clay loam and, in some cases, silt clay loam and sandy clay loam. Cemented soils such as caliche and hardpan are also considered Type A. However, no soil is Type A if: The soil is fissured; or The soil is subject to the effects of vibration from heavy traffic, pile driving, etc.; or The soil has been previously disturbed; or The soil is part of a sloped, layered system where the layers dip into the excavation on a slope of four horizontal to one vertical (4H:1V) or greater; or The material is subject to other factors that would require it to be classified as a less stable material. Type B means: Medium stiff to stiff cohesive soil with an unconfined compressive strength greater than 0.5 tsf (48 kpa) but less than 1.5 tsf (144 kpa); or Granular cohesionless soils including: angular gravel (similar to crushed rock), silt, silt loam, sandy loam and, in some cases, silty clay loam and sandy clay loam. Previously disturbed soils except those which would otherwise be classed as Type C soil. Soil that meets the unconfined compressive strength or cementation requirements for Type A, but is fissured or subject to effects of vibration; or Dry rock that is not stable; or Material that is part of a sloped, layered system where the layers dip into the excavation on a slope less steep than four horizontal to one vertical (4H:1V), but only if the material would otherwise be classified as Type B. Type C means: Soft cohesive soil with an unconfined compressive strength of 0.5 tsf (48 kpa) or less; or Granular soils including gravel, sand, and loamy sand; or Submerged soil or soil from which water is freely seeping (may not be stable except at a much flatter slope than 1.5H:1V), or Submerged rock that is not stable, or Material in a sloped, layered system where the layers dip into the excavation or a slope of four horizontal to one vertical (4H:1V) or steeper. Florida and Louisiana have mostly Type C soil material, which requires a slope no steeper than 1.5 H:1 V. For every 1.5 feet horizontal, the vertical should drop no more than 1 foot down. Safe sloping criteria are a function of the conditions, soil types, water content of materials, and water table. If not sure of the excavation safety, check with the competent person before entering the excavation. (Per Appendix B in 29 CFR 1926 OSHA Construction regarding sloping excavations) Type C soil sloping of an excavation is 1.5H:1V slope or 34 degrees

4 Page 4 Injury Incidents: None for July! Great Job Everyone! Vehicle/ Equipment/ Property Incidents: Ardaman Update Employee was preparing to make a left hand turn through an intersection. The oncoming traffic in the opposite direction also had a green light. Our driver stropped in the intersection and tried to avoid the other vehicle that was traveling straight, but was unable to do so. Vehicles that are traveling in the thru lanes have the right of way over other vehicles trying to turn. Remember to look straight ahead, and left, right, left when approaching intersections to ensure they are clear before proceeding through them. Employee was traveling in the middle lane at the posted speed limit on the interstate. Another vehicle came speeding up from behind and struck the passenger side of our vehicle. Remember to get the big picture and maintain awareness around your entire vehicle. Keep your eyes moving and be aware of vehicles approaching behind you. Employee was backing his truck from a parking space and struck a sign. Before backing always walk around the vehicle to ensure the area is clear. If the vehicle is equipped with a back up sensor and you hear it beep, immediately stop the vehicle and check your mirrors to ensure the area is clear behind the vehicle. If nothing is seen in the mirrors, stop and get out of the vehicle and conduct a LMSA and walk around the vehicle. Employee was hand augering at a private residence. While hand augering, the employee struck a small gas line that had been installed by the homeowner and was only located 6 below the surface. When working on private property communicate with the owners to see if additional drawings or information can be provided in relation to utility locations. It is noted that the 811 call-in ticket was created for this project, however the ticket was not printed and on site. This is a violation of company policy. The printed call-in ticket is the last line of defense for a worker to reference/verify if utilities may be present and marked properly. Employee had the front passenger wheel come off of the truck while driving on the interstate. The employee carefully moved to the shoulder of the road and was able to bring the vehicle to a stop safely. When changing wheels and tires, follow the JSA on changing a flat tire and to torque/tighten the lug nuts to the manufacturer s specifications. Employee vehicle had become stuck on site in sugar sand. A wrecker service was contacted to free the vehicle. While moving the vehicle, the wreck operator attached the tow cable to the front axel and it came loose and tore the front bumper. When towing a vehicle, try to use the established tow hook areas on the vehicle provided and/or recommended by the manufacturer. If unsure of the location, consult the owners manual in the glove box. Safety Audits: Identified Hazards from 21 Safety audits conducted in the month of July. Ergonomics: Employee was observed using poor techniques while using the pipe wrench on the drill rig. Remember to grasp the butt end of the pipe wrench handle when attaching the wrench to the drill rod in the hole. If the drill rod or wrench slips, the proper hand placement keeps your hand out of the line of fire with the mud tub below. Housekeeping: Employee observed slip/trip hazard created from concrete debris in the concrete area. Housekeeping in areas should be completed throughout the work day to reduce hazards. Housekeeping: Employee observed water on the floor prior to performing task. Employee failed to remove the hazard prior to performing the task. When performing tasks, it is important to first remove all hazards to ensure the work area is clear and safe. Once work has commenced, the employee s focus tends to be on the task itself and as a result, awareness of work place surroundings is reduced. Fall: Employee failed to observe another contractor on site using an incorrect ladder and entering a confined space without proper authorization and training. Although we may not have authority over the other contractor, our STOP program asks that Individuals are willing and empowered to intervene to ensure their safety and the safety of others. IF IT S NOT SAFE, STOP. DON T DO IT THAT WAY.

5 Page 5 Near Miss/ Hazard Identification: Highlighted Near Misses from 32 reports received for the Month of June Ardaman Update Continued Employee observed a piece of equipment at the asphalt plant being staged for installation the following day. The equipment was left with the bubble wrap and other packing along side of the walkway where temperature sampling of the dump trucks is performed. Upon further inspection a metal band was also laying across the walkway hidden in the plastic bubble wrap. Facilities supervisor was contacted. Proper housekeeping is key in providing a safe work surface. Always discard all garbage and debris if it is unsafe, and at least before leaving the work area for the day. Employee observed an earthwork contractor on a job site. One of the workers was showing symptoms of heat stroke. The contractor was notified and the worker was taken to the hospital for observation. Working outdoors in the heat is very dangerous. Remember to always drink plenty of water (8 ounces every minutes), use cooling devices to help combat the heat (cool wraps and brim extensions), and take sufficient breaks in the shade. Employee observed that the new winch cable lines supplied for the drill rig by a vendor were different. The new cables tend to tighten under a load and cause the hook swivel point to spin. The spinning occurs both times when a load is put on the cable and when released. This would cause any rod and equipment attached to the swivel hook to spin creating a struck by, pinch, or laceration hazard. Cable supplier was contacted and a new cable was supplied. Cables for drill rigs must be labeled as non-rotating hoist cables. Employee was classifying soils from sample jars in the lab. The employee found a 1 1/2 glass shard in the jar. When sampling is performed in the field and debris may be present, notes should be made on the drill log. These notes allow other individuals analyzing the sample to understand the necessary precautions that will be needed to reduce exposure to the hazard. Employee observed that a roadway on the job site had been washed out from the previous night s rain. Access to the road was restricted and the contractor was contacted to stabilize the road for safe travel. When erosion or washouts on roads occur do not enter/cross them until further inspection can verify that the area is stable and safe. Employee observed a broken tail gate chain on a large haul truck on site. The chain was swinging around as the haul truck traversed the site and at times was rubbing the tire of the truck. Our employee was able to get the operator s attention to stop the truck and the contractor supervisor had the truck removed from operation and the Manufacturer was contacted for repairs. Equipment that is not operating safely should not be used and should be tagged out of service. If it is Ardaman s equipment notify your supervisor. Take Precautions to Avoid Heat Stress when working in hot conditions: Use general ventilation, cooling fans, and evaporative cooling whenever possible; Shield heat producing equipment; Drink water steadily before and during work in the heat: Drink about 16 ounces before starting and 5 to 7 ounces every 15 to 20 minutes during hot work activities. On average we lose 1 quart of water per hour in hot conditions. Eat well-balanced meals, avoiding heavy or hot food, alcohol and caffeine; Work at a steady pace minimizing overexertion; Know your own limits and ability to work safely in heat; Take fast action for symptoms of heat cramps, exhaustion, or heat stroke. Safety Question Answer: A A competent person (defined by OSHA) inspects the excavation before any workers enter. A competent person is one with the experience to identify hazards and precautions and the authority to take necessary corrective measures.

6 August 2016 Safety Quiz Please circle the letter of the answer that fits best. Some answers can be found in the newsletter 1. A competent person is responsible for checking the excavation before entry, and takes action if safety problems are identified. A. True 2. Which systems can be used for protecting workers in an excavation or trench greater than 4 feet in depth? A.Trench Box or Shoring B. Sloping or benching C. Nothing is needed D. A&B 3. Excavations deeper than 5 ft. in depth must have protective systems in place. 4. At a minimum, daily inspection of tools and equipment should be performed to verify proper and safe operation. A. False B. True 5. Excavated materials and equipment must be kept at least? A. 2 inches from the edge of the hole B. 2 feet from the edge of the hole C. 20 from the edge of the hole D. All the above 6. A safe means of entry and exit must be provided for an excavation. 7. What type of soil is commonly found in Florida and Louisiana regarding OSHA Classifications? A. Type B B. Stable Rock C. Type A D. Type C 8. Barricades should be used to guard an excavation if mobile equipment can come in contact with the edge. 9. You should leave an excavation promptly and properly if you feel that it is unsafe. 10. A ladder cannot be further than feet from a worker that is down inside an excavation or trench and must extend 3 feet above the surface and be secured. A.10 B. 25 C. 30 D. It does not matter 11. What is an employee s last line of defense when exposed to hazards? A. Training B. Engineering Controls C. PPE D. None All Ardaman employees must complete the quiz and turn it in by the end of each month. For those individuals who cannot attend the monthly safety meeting please complete the quiz and submit it to your supervisor for approval. These will be sent to HR/H&S. All others must submit the quiz at the designated location at your office. The supervisor only needs to sign the quiz if you are unable to attend the meeting, you must explain the reason in the box below: Print Name Here Sign Name Here Date Supervisor Print Name Here Supervisor Sign Name Here Date