Digging a 10' Trench. What degree should I slope back shoring?

When digging a 10-foot trench, the sloping or shoring requirements depend on the soil type and other conditions 5, 6, 7. Here's a breakdown of factors to consider:

1. Soil Classification: A "competent person" must classify the soil as Stable Rock, Type A, Type B, or Type C [1]. This classification is crucial for determining the appropriate slope [2].

2. Sloping Options:

• Option 1 (Allowable Configurations and Slopes): You can slope the excavation at an angle no steeper than 1 1/2 horizontal to one vertical (34 degrees) [3]. This is generally for Type C soil [3].
• Option 2 (Appendices A and B): Use the guidelines in OSHA's appendices for maximum allowable slopes and configurations [3].
• Option 3 (Tabulated Data): Follow tabulated data (tables and charts) approved by a registered professional engineer [3]. A copy of this data must be available at the job site [3].
• Option 4 (Design by a Registered Professional Engineer): Have a registered professional engineer design the sloping and benching system [3]. The design must be in written form and include the slopes and configurations determined to be safe [3].

3. Maximum Allowable Slopes: The maximum allowable slope depends on the soil type [2]:

• Type A Soil: Maximum slope of 3/4:1 (horizontal to vertical) [4]
• Type B Soil: Maximum slope of 1:1 (horizontal to vertical) [5]
• Type C Soil: Maximum slope of 1 1/2:1 (horizontal to vertical) [3]
• Stable Rock: Vertical sides are allowed if the rock is stable [6].

4. Shoring Systems: As an alternative to sloping, you can use a shoring system [6]. This involves installing supports to prevent cave-ins [6].

5. Competent Person: A "competent person" must inspect the excavation daily for any signs of potential cave-ins or other hazards [7]. They also need to be able to identify existing and predictable hazards in the surroundings [8].

6. Additional Considerations:

• Surface Encumbrances: Remove or support any surface encumbrances that could be a hazard [9].
• Underground Installations: Identify and locate any underground utilities before excavating [9].
• Water Accumulation: Take precautions to prevent water accumulation in the excavation [10].
• Adjacent Structures: Ensure the stability of nearby structures [10].

Disclaimer: Regulations can vary and it is important to check with your local authorities for any specific requirements in Maryland.