• During construction projects where excavation is required, there are three standard systems approved by the Occupational Safety and Health Administration (OSHA) to prevent the sides of excavated trenches from caving in on the employees. Of these, shoring is used when the others are impractical. There are two main OSHA-approved types of shoring.
  
  

Excavation requirements

• Before a shoring system can even be used, there are specific excavation requirements to be met. Some of these requirements that are meant to safeguard employees include: removing or supporting surface encumbrances; protecting all nearby underground utilities such as sewer, telephone, electric and water lines that could be encountered during shoring; installing safe lateral means of egress and access to the trench that are not deeper than 25 feet, such as a stairway, a ladder, or a ramp; and equipping employees with highly visible reflective gear to protect them from public vehicular traffic.
  
  

Timber shoring requirements

• The first OSHA-approved system is timbering shoring. Before it can be utilized, there will be soil classification conducted to determine the soil or soils that will be dug into. This soil classification will determine everything from the size and kind of timber used to the placement of the timber.
  
  If it is determined that normal timber that is in accordance with specifications of the National Bureau of Standards, employees are permitted by OSHA to use soil classification tables C--1.1 - C--1.3 located in Subpart P to determine which approved timber can be used. If the soil classification requires different timber to be used, employees are given the choice of either using soil classification tables C--2.1 - C--2.3, or tables provided by the Army Corps of Engineers or the Bureau of Reclamation.
  
  Each table shows not only the proper size of timber to be used, but also the placement of such timber.
  
  

Aluminum hydraulic shoring requirements

• The second OSHA-approved system is aluminum hydraulic shoring. While timber shoring can be used in trenches up to 24 feet in depth, aluminum hydraulic shoring can only be used in trenches no more than 20 feet deep. And, like timber shoring, aluminum hydraulic shoring requires a preliminary soil classification to determine exact procedures that will be followed. However, soil classification tables D--1.1 and D--1.2 will be used when a vertical shore rails are present, and tables D--1.3 and D--1.4 will be used when horizontal waler systems are present.
  
  Regulations stipulate that when a 2-inch hydraulic cylinder is used, it should have a 2-nch inside diameter with at least 18,000 pounds of axial compressive load at maximum extension. And, when a 3-inch hydraulic cylinder is used, the load should be at least 30,000 pounds.
  
  

Alternative types of shoring

• There are three alternative methods of shoring trenches allowed by OSHA regulations. They are pneumatic shoring, trench screw jacks and underpinning. However, since these methods are not normally used, the OSHA regulations do not elaborate on specifications for their usage.