Other Safety Information
Serious Injury or death can result from failure to familiarize and comply with safety regulations and guidelines before erecting, using or dismantling scaffolding. Scaffolding must be erected, moved or dismantled only under the supervision of a competent person.
The competent person must have the ability to identify existing and predictable hazards and have the authority to make necessary corrections; including stopping the job, until such corrections are made. OSHA requires that the competent person be capable of making decisions on issues regarding fall protection, scaffolding integrity and safe accesses to the scaffolding. The competent person must be familiar with the manufacture specifications and instructions for the safe use of scaffolding. Usually the competent person will be someone with combination on-the-job experience and numerous training credits.
The job site should be inspected for ground conditions, strength of the supporting building, proximity to power lines (minimum distance of 10 feet must be maintained between energized power lines and the scaffolding) and overhead obstructions. Wind conditions and weather protection covering are also important considerations. Frame spacing and mudsill size can only be determined after calculating the total loads to be imposed on the scaffolding and the strength of the structure. The load carrying capacity information for scaffolding components is available from the manufacturer.
Stationary or fixed scaffolding over 125 feet in height and movable or rolling scaffolding over 60 feet in height must be designed by a professional engineer. Before erecting scaffolding all equipment must be inspected to make sure that they are in good condition and are serviceable. Damaged or deteriorated equipment should not be used. Wood planks used for scaffolding must be specifically approved and marked by an approved grading agency.
Everyone who is erecting moving or dismantling or using scaffolding must wear hardhats. Special care must be taken when erecting scaffolding on soft, frozen or filled ground. Sills must be level and in full contact with the supporting surface. Base plates and screw jacks with base plates must be in firm contact with both sills and the legs of the scaffolding. Only screw jack must be used to compensate for uneven ground. Unstable objects like wooden blocks, bricks or stones must not be used.
The height of the tower must not exceed four times the base width. Out riggers may be used on both sides of the tower to increase the base width when necessary. All casters must be secured to the frame or screw jacks with nuts and bolts or other secure means. The weight including the load of the tower must not exceed the capacity of the casters. Casters must be locked unless the scaffold is being moved. All frames of the tower must be cross-braced.
- OSHA requires that scaffolding to be secured to the building when the height of the scaffolding exceeds four times the minimum base width.
- The bottom tie to the building must be placed no higher than four times the minimum base width and every 26 feet vertically thereafter. The ties must be placed as close to the top as possible in case they are less than four times the minimum base width of the scaffolding.
- Vertical ties must be placed at the end of the scaffolding and at no more than 30 feet horizontal intervals.
- The ties must be installed as the erection progresses and not removed until the scaffolding is dismantled to that height.
- Side brackets, cantilevered platforms, pulleys or hoists and wind conditions must be considered and compensated with additional ties/or guides.
- Circular scaffolding erected completely around or within the structure must be restrained from tipping by using "stand-off" bracing members.
- Guardrails are required on welded frame scaffolds that are 10 feet high or more. Top rail height must be 36 inches to a maximum of 45 inches. Top rails must be able to withstand at least 200 pound of out ward pressure and mid rails at least 150 pounds.
- Cross bracing is acceptable in place of guardrails, if the cross bracing is between 20 and 30 inches above the platform. Cross bracing between 38 and 48 inches above the platform may serve as the top rail.
- For scaffolding over 10 feet, each employee must be protected by the use of personal fall protection systems when guard rail are not provided.
- In addition to wearing hard hats, each employee on a scaffold shall be protected from falling hand tools, debris and other objects by erecting toe-boards or screens.
- Spaces between scaffold planks must be no more than one inch. An uncleated scaffold plank must extend over the end support a minimum of 6 inches.
- Scaffold platforms above one section high must be provided with safe access by providing ladders or stair cases. When hood-on ladders are used, there must be a rest platform every 35 feet.
- The scaffold distance from a 220-volt line must be at least 3 feet.
- Workers must not be permitted in winds above 30 MPH.
- Pre shift inspections must include checking the following:
A) Base plates and mudsills for proper placement and stability.
B) Cross bracing to make sure the structure is square.
C) Guardrails for secure construction and proper placement.
D) Platforms for splits, cracks and worn or damaged areas.
Trenching and Excavation Safety
About 400 workers die every year in the U.S. and about 6500 are seriously injured in trenching and excavation related accidents. If you are in a trench when a wall collapses you may get buried in soil very quickly. One cubic yard of dirt could weigh approximately 2,800 pounds-about the same as a small pickup truck! In addition to the obvious danger of getting buried by soil, there are other potential dangers when working in trenches, such as hazardous gas inhalation, falling objects, drowning, dangerous equipment and power sources like electricity. OSHA requires trench protection in all excavations and trenches deeper than 5 feet. However, even in excavation and trenchers less than 5 feet deep, trench protection may be required depending on the soil type and presence of water.
OSHA classifies soil types into 3 categories "A," "B" and "C," "A" being the most stable and "C" being the least stable. The competent person in charge of the job (person who has proper training to identify soil types and other excavation and trenching hazards and has the authority to take prompt action, including stopping of the job) has to identify the soil type and select the correct protective system for the trench or excavation.
Sloping, benching, shoring and shielding are the main protective systems used. The type of the soil determines the sloping angle. Shoring is designed to prevent walls from collapsing. Shoring can be made out of timber or hydraulically or mechanically-operated metal jacks. Shielding or trench boxers are used to protect workers from collapsing walls. The tabulated data on the shoring and shielding provided by the manufacturer or the design professional engineer must be followed regardless of the soil classifications.
- Trenches over 4 feet deep must have exists within 25 feet of every worker by way of ladder or ramp.
- Underground utilities should be marked by the "Blue Stake Organization" before the beginning of the excavation.
- Any excavation under a base or a foundation or a wall requires a support system designed by a registered professional engineer.
- Excavation spoils must be placed at least 2 feet away from the trench opening.
- Hard hats are required in every trenching and excavation work zone and traffic vests are required when working in street areas.
- Before beginning of an excavation, look out for overhead power lines and make sure that there is enough clearance to work under the power lines.
- No one should be allowed under the loads handled by the digging or loading equipment.
- Barricade tape, barricades and fences should be used to prevent unauthorized persons from getting inside the work area.
- Heavy vehicles which create vibrations should not be allowed close to excavations.
- The "Competent Person" must examine the excavation site every morning and after rain or changing conditions, such as water in the excavation, for signs of earth movement and movement of shoring.
A hazardous atmosphere can be present or develop in a trench or an excavation specially when digging close to a landfill, toxic site or a sewer. It can also develop if chemicals are used inside or close to the trench or excavation. Oxygen deficiency, presence of toxic or highly flammable gases (such as carbon monoxide, hydrogen sulfide, methane and solvent vapors) are the main contributors to hazardous atmospheres. Testing for such hazardous atmospheres should be done and if such problem exist it should addressed by providing fresh air ventilation or using personal protective equipment.
Any type of energy source found in a trench or an excavation should be properly locked out and tagged out.