A euphemism for an industry that specializes in underground excavation and trenching is “ditchdigger.” They practice their trade on a day to day basis, placing a myriad of piping underground, which comprises the grid network of sub-surface utilities (gas, light, power, storm, sewage, telephone, fiber optic, steam, etc.). All of these utilities are placed in “trenches.”
What are some other guidelines and procedures that must be put in place either prior to excavation or during the excavation process as it occurs? Here’s a short list of “must” items:
• 20-Foot Max – Trench shore systems in trenches more than 20 feet must be designed by a Registered Professional Engineer.
• Aluminum Hydraulic Shores – One of four options to prevent trench collapse.
• Benching – Benching dimensions are shown on Tables B-1, B-2, and B-3 in Subpart P (Excavation) Standard. NOTE: No “benching” in Type C Soil.
• Confined Spaces – Manholes, pits, shafts, tunnels, large-bore pipe are determined by OSHA to be (by definition) “confined spaces.” As such, before entering, workers may be required to test the atmosphere, use spark-proof tools and practice emergency exiting procedures.
• Gas Cans – Gasoline and similar combustible liquids, must be stored in a metal spring-loaded container with a flash-arrestor in the nozzle, and be clearly labeled as to their contents.
• Ladders – Extension ladders must be placed in all trenches four feet or more deep.
• Maximum Allowable Slopes – Vary depending on type soil.
• One-Call System – Before “digging” the nearest One-Call Center must be notified, to call for marking of existing underground utilities.
• Personal Protection Equipment – PPE on excavation sites should include (but is not limited to) wrap-around safety goggles, hearing protection, hard hats, work gloves, heavy-duty work boots, appropriate work clothing, respirators, etc.
• Pocket Penetrometer – Spring-loaded device used to test for type of soil:
- Type A Soil 1.5 tons per square feet (unconfined compressive strengths)
- Type B Soil .5 to 1.5 tons per square feet (unconfined compressive strengths)
- Type C Soil .5 or less tons per square feet (unconfined compressive strengths)
• Ramps – Soil ramps may be used to access and exit trenches (with limitations).
• Soils Classification – Four types of soils and must be determined prior to excavation.
• Spoil Pile – Soil excavated from trench must be placed a minimum of 2 feet back from the lip of the trench wall.
• Superimposed Loads – No superimposed loads (i.e. pipe, vehicles, compressors, sleds, cement trucks, etc.) should be closer than two feet to lip of the trench wall.
• Tabulated Data Sheet – Must appear on all trench shields, indicating depth of trench the shield can be used in depending on type of soil.
• Timber Shores – One of four options to prevent trench collapse.
• Trench Shields – One of four options to prevent trench collapse.
Did you know that a cubic yard (3’ x 3’ x 3’) of soil weighs approximately 3,000 pounds? A cubic yard of soil falling (crashing down) on a worker will probably suffocate a worker in an instant, or kill him outright. Trenches five feet or more deep must be shored prior to entry. NO EXCEPTIONS.
Some construction activities are more hazardous than others. Even under the best of conditions, excavation is highly dangerous. Ongoing training regarding hazards is a “must” for all workers. Using the “buddy system” is particularly good for these workers…particularly “new-hires.”