Trade Exam · Module 3
Underground Installation Safety
Dig safely and legally in California: notify 811 at least two working days (and not more than 14 calendar days) before you excavate, hand dig within 24 inches of the marks, get the Cal/OSHA permit for trenches 5 feet or deeper that workers enter, classify the soil as Type A, B or C, slope at 3/4 to 1, 1 to 1 or 1-1/2 to 1 or use shoring or a shield, keep spoil 2 feet back, provide a ladder within 25 feet in trenches 4 feet deep, have a competent person inspect daily and after rain, and backfill the way the plumbing code requires.
Key Takeaways
- Delineate the dig area, then notify the regional notification center (811) at least 2 working days and not more than 14 calendar days before excavating; a ticket is valid 28 days (Gov. Code 4216.2).
- Within the tolerance zone, 24 inches on each side of the operator's marks, find the line with hand tools before using power equipment (Gov. Code 4216, 4216.4).
- Trenches or excavations 5 ft or deeper that any person must descend into need a Cal/OSHA permit (Title 8, 341).
- Protect workers from cave-ins with a protective system unless the excavation is in stable rock, or is under 5 ft deep and a competent person sees no sign of a potential cave-in (1541.1).
- Maximum slopes (Appendix B): Type A 3/4:1 (53 degrees), Type B 1:1 (45 degrees), Type C 1-1/2:1 (34 degrees). Over 20 ft deep needs a registered professional engineer.
- Ladder or other egress in trenches 4 ft or deeper within 25 ft of lateral travel; spoil and equipment at least 2 ft from the edge (1541).
- A competent person inspects daily before work starts and after every rainstorm (1541).
Why This Matters
Safety is its own section of the C-36 trade exam (17 percent), and the study guide lists "excavation and underground installations" in Underground and Rough Systems (22 percent). The study guide's reference list includes the Cal/OSHA Construction Safety Orders and the Underground Service Alert rules in Government Code 4216. Trench work is where plumbing contractors face some of the most serious hazards on any job: cave-ins, struck utility lines and bad air. This lesson uses the current text of those rules.
Before You Dig: 811
California's excavation law is Government Code Section 4216 and the sections after it.
- Mark the area first (4216.2): before notifying the regional notification center, the excavator delineates the area to be excavated.
- Notice window (4216.2): notify the center at least two working days, and not more than 14 calendar days, before starting. Working days are Monday through Friday, 7:00 a.m. to 5:00 p.m., excluding federal and state holidays (4216). An excavator and operator may agree to a different start date, and the notice rule does not apply in an emergency.
- Ticket life (4216.2): a ticket is valid for 28 days. If work continues, renew it through the center's website or by calling 811 by the end of the 28th day.
- Wait for responses (4216.2): unless there is an emergency, do not start until all operators of subsurface installations have fulfilled their obligations. Cal/OSHA 1541(b) likewise bars opening the excavation until the area is marked and all known operators have responded.
- Tolerance zone (4216, 4216.4): the tolerance zone is 24 inches on each side of the operator's field marking. Within it, find the exact location of the installation with hand tools before using any power driven excavation or boring equipment, subject to the narrow exceptions in 4216.4 (for example, approved vacuum excavation, or removing pavement with no known installation in it).
- If you hit something (4216.4): notify the operator immediately of any damage, including nicks, dents and gouges. If a gas or hazardous liquid line releases its contents, or a high priority installation is damaged, call 911 immed
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