How steep the simple trench bank may be, in one paragraph
For the standard excavation, the bank must not be steeper than one and one-half horizontal to one vertical (34 degrees measured from the horizontal). According to California Department of Industrial Relations, this specific angle applies unless the employer selects one of the other protective options listed in the regulation. The Washington State Legislature prints the same numerical limit, stating that excavations must be sloped at an angle not steeper than 1 1/2 horizontal to one vertical, or 34 degrees measured from the horizontal, according to Washington State Legislature. Both sources tie this 34-degree line to the simple slope method, distinct from other protective systems.
Key takeaways for choosing the trench slope before anyone works on the face
- 34-degree slope limit: For simple excavations, the bank must not be steeper than one and one-half horizontal to one vertical, which is 34 degrees measured from the horizontal, according to California Department of Industrial Relations.
- 5-foot condition: Excavations less than 5 feet in depth and examination of the ground by a competent person provides no indication of a potential cave-in, according to California Department of Industrial Relations.
- Design copy on site: At least one copy of the design must be maintained at the jobsite while the slope is being constructed, according to California Department of Industrial Relations.
- Daily record: Write the trench location, the slope you set, and which page you used before anyone works the bank.
You cannot treat the 34-degree line from one page as the universal wording for every jurisdiction or regulatory appendix. The federal appendix does not print the words "34 degrees" in the same manner as these state pages. Each publisher’s text is distinct, and you must verify which specific page governs your site. Do not assume that a 34-degree cut is safe in every soil type without checking the specific soil classification and the corresponding slope requirements for that condition. The 34-degree figure is a printed limit for the simple slope option, not a blanket safety guarantee for all excavation scenarios.
The slope angle or ratio each page prints
The wording for the simple trench slope varies by jurisdiction, and you must read the specific text printed on the page you are using. Do not assume that a number from one state applies to another. California, Washington, and the federal appendix print an angle or a ratio in the lines below.
California Code of Regulations, Title 8, Section 1541.1. Requirements for Protective Systems, prints the rule for excavations. It states that excavations shall be sloped at an angle not steeper than one and one-half horizontal to one vertical. The page includes the specific measurement in parentheses: 34 degrees measured from the horizontal. This applies unless the employer uses one of the other options listed below, according to California Department of Industrial Relations.
WAC 296-155-657: prints a nearly identical line for its jurisdiction. It states that excavations must be sloped at an angle not steeper than 1 1/2 horizontal to one vertical. Like the California text, it includes the parenthetical measurement: 34 degrees measured from the horizontal. This rule applies unless the employer uses one of the other options listed below, according to Washington State Legislature.
The federal source prints different language for specific depth ranges. 29 CFR Appendix B to Subpart P of Part 1926 - Sloping and Benching addresses excavations more than 8 feet but not more than 12 feet in depth. It specifies that unsupported vertically sided lower portions shall have a maximum allowable slope of 1:1. It also sets a maximum vertical side of 3, according to Legal Information Institute. This page does not print the words "34 degrees" for this specific 8-to-12-foot range in the provided quote.
The same federal appendix includes an exception for short-term excavations. It states that simple slope excavations which are open 24 hours or less and which are 12 feet or less in depth shall have a maximum allowable slope of a specific value. The provided quote cuts off before printing the final number for this exception, according to Legal Information Institute. You must check the full text of that page to see the exact ratio printed for this short-term exception.
Ohio Administrative Code, Rule 4123:1-3-13, prints a different measurement unit. It references a horizontal distance of each one-half-foot (15.2 centimeters) horizontal. This quote does not print a degree angle or a simple ratio like 1.5:1 in the provided text, according to Ohio Administrative Code.
The shallow-cut exception and the shield height
The 5-foot rule applies when the excavation is less than 5 feet in depth and an examination of the ground by a competent person provides no indication of a potential cave-in, according to California Department of Industrial Relations. This specific condition is the shallow-cut line printed on that page. If the ground examination reveals any indication of a potential cave-in, the no-indication condition is not met.
When you use a shield system instead of sloping the bank, the sides of the shield must extend a minimum of 18 inches above the vertical walls of compound excavations, according to California Department of Industrial Relations. This 18-inch extension is a specific dimensional requirement for the shield structure itself. The federal appendix provides a similar requirement for support or shield systems, stating that the support or shield system must extend at least 18 inches above the top of the vertical side, according to Legal Information Institute. Both sources specify the same 18-inch minimum height for the shield extension above the vertical wall.
Check the depth of your trench before you compare it with the under-5-foot condition. If the depth is under 5 feet, perform the ground examination by a competent person to see if there are any indications of a potential cave-in. If you choose to use a shield, measure the extension of the shield sides to ensure they meet the 18-inch minimum requirement above the vertical wall. Write down the depth, the result of the ground examination, and the shield extension measurement in your daily log. This record helps you verify that the protective system meets the specific requirements for the conditions you found.
A filled reference table of the slope lines
The table below lists the slope words, depth or shield numbers, and design copy requirements printed by each publisher. Use it to verify which page supports your current trench plan.
| Publisher | Slope words it prints | Depth or shield number it prints | Whether it says to keep a design copy on site |
|---|---|---|---|
| California Department of Industrial Relations | one and one-half horizontal to one vertical (34 degrees measured from the horizontal) | a minimum of 18 inches | At least one copy of the design shall be maintained at the jobsite while the slope is being constructed. |
| Washington State Legislature | 1 1/2 horizontal to one vertical (34 degrees measured from the horizontal) | illustrative: no depth figure in the supplied quote | You must maintain at least one copy of the design at the job site while the slope is being constructed. |
| Legal Information Institute | maximum allowable slope of 1:1 | 18 inches above the top of the vertical side | illustrative: no design-copy line in the supplied quote |
Keeping a copy of the design on the job
According to the California Department of Industrial Relations, at least one copy of the design shall be maintained at the jobsite while the slope is being constructed. The Washington State Legislature states the same requirement in its WAC 296-155-657, noting that you must maintain at least one copy of the design at the job site while the slope is being constructed.
This requirement applies specifically to the period of construction. If you are building the bank today, the paper or digital copy of the design needs to be physically present where the work is happening. It is not enough to have the design filed in the office or stored on a phone that is not accessible to the crew. The copy serves as the reference for the specific angle and support details.
The copy on site allows the competent person to verify that the construction matches the intended design. If the design changes, the copy at the jobsite must be updated to reflect the new instructions.
Illustrative example of reading the slope figures together
Picture a trench 12 feet deep. For a cut more than 8 feet but not more than 12 feet, the printed line gives a maximum allowable slope of 1:1 and a maximum vertical side of 3. A shield extends 18 inches above the top of the vertical side. Below a support, the extra dig is 2 feet, and the design covers the full depth with no soil loss while the trench is open. A second cut is 4 feet deep, so read the under-5-foot line and still ask a competent person whether the ground shows any indication of a potential cave-in. These figures are illustrative only and name no firm.
What to write for today's slope check
Write the trench location, the soil call you are using, the slope you set, and the page you used before anyone works the bank. For a fuller daily note, use Construction Daily Log Checklist for Supervisors, and keep a separate before-work list such as Portable ladder checks: 4 steps before climbing. The California Department of Industrial Relations states that excavation of material to a level no greater than 2 feet below the bottom of the members of a support system shall be permitted, but only if the system is designed to resist the forces calculated for the full depth of the trench, and there are no indications while the trench is open of a possible loss of soil from behind or below the bottom of the support system, according to California Department of Industrial Relations. Record this specific depth limit and the design requirement in your daily log. If you are using a support system, verify that the design accounts for the full trench depth, not just the visible cut. Note any indications of soil loss from behind or below the bottom of the support system while the trench is open. These observations must be documented to confirm the system remains safe for continued work.
FAQ about the trench slope
Where is the 34-degree line printed?
The phrase "34 degrees measured from the horizontal" appears in the text of the California Code of Regulations, Title 8, Section 1541.1, as published by the California Department of Industrial Relations. This specific angle is part of the slope requirement for excavations under that state's protective systems rules. You should verify the exact wording on the page you are using for your site plan.
What does the federal appendix say instead?
The federal appendix does not use the 34-degree phrasing for the same depth range. Instead, it specifies a maximum allowable slope of 1:1 for excavations more than 8 feet but not more than 12 feet in depth, according to the Legal Information Institute. This 1:1 ratio applies to unsupported vertically sided lower portions in that specific depth band. Do not substitute the state's degree measurement for the federal ratio when citing the appendix.
What is the under-5-foot line on the California page?
Excavations are less than 5 feet in depth and examination of the ground by a competent person provides no indication of a potential cave-in. This condition is listed as a specific scenario in the California Department of Industrial Relations text. If the competent person identifies a potential cave-in, the no-indication part of that line is not met.
What should I write down today?
Record the trench location, the slope you set, and the specific page you used for the decision. The California Department of Industrial Relations requires that at least one copy of the design be maintained at the jobsite while the slope is being constructed. Writing these details into your daily log helps you keep the required design copy accessible and traceable.