Benches must be below the maximum allowable slope for that soil type. Benching is not allowed in Type C soil. Shoring involves setting up a structure that supports the sides of excavations to prevent cave ins. Shielding involves the use of a structure that is able to withstand the forces imposed on it by a cave-in and thereby protect employees. This equipment ics commonly referred to as a trench box.
Soil classification is required when shoring or shielding is used.
Appendix A outlines the requirements for soil classification. Appendix C provides Tables that provide specifications for the cross braces, wales and uprights based on the soil type and trench depth. This information must be kept at the job site while the protective system is being constructed. After that time, the information can be kept off site, but must be made available upon request by an OSHA inspector. Any deviations from the manufacturer data can only be made with the written permission of the manufacturer.