CSLB General Building (B) — All Questions

An excavation for a sewer lateral is dug to a depth of 6 ft in Type C soil. At what depth does OSHA require protective systems (sloping, shoring, or a trench box) for workers entering the trench?

• a.Any depth over 2 ft
• b.Any depth over 3 ft
• c.Only over 10 ft
• d.5 ft or more (and any depth if a competent person sees a hazard)✓

OSHA requires cave-in protection for any trench 5 ft or deeper, and at any depth if a competent person identifies a hazard, so a 6 ft trench must be sloped, shored, or shielded. Trenches less than 5 ft may be exempt only if a competent person finds no cave-in potential. Soil type sets the required slope angle.29 CFR 1926.652

A trench is dug in Type C soil, which OSHA requires to be sloped at 1.5 to 1 (horizontal to vertical). For a trench 8 ft deep, how wide must the sloped opening be beyond the trench bottom on each side?

• a.12 ft each side✓
• b.8 ft each side
• c.4 ft each side
• d.16 ft each side

At 1.5 to 1, horizontal run = 1.5 x depth = 1.5 x 8 = 12 ft of slope on each side beyond the trench bottom. Type C is the least stable soil and requires the widest, flattest slope. Type A allows 0.75 to 1 and Type B 1 to 1, so knowing the soil class sets the excavation width.29 CFR 1926.652

A trench is 3 ft wide, 6 ft deep, and 40 ft long. How many cubic yards of spoil are generated (27 cubic feet per cubic yard), a figure needed to plan the 2 ft edge setback and haul-off?

• a.8.9 yd^3
• b.26.7 yd^3✓
• c.17.8 yd^3
• d.32.0 yd^3

Volume = 3 x 6 x 40 = 720 ft^3, and 720 / 27 = 26.7 cubic yards of spoil. This volume determines how much material must be set back at least 2 ft from the edge or hauled away so its surcharge load does not collapse the wall. Underestimating spoil crowds the edge and endangers workers.29 CFR 1926.651

A plumber must enter a sanitary sewer manhole to make a connection. This is a permit-required confined space. What atmospheric hazard is the leading concern, and what is required before entry?

• a.Excess oxygen only, no testing needed
• b.High humidity; wear a raincoat
• c.Toxic/flammable gases (hydrogen sulfide, methane) and oxygen deficiency; test the atmosphere and ventilate before and during entry✓
• d.Noise; wear earplugs

A sewer is a permit-required confined space where hydrogen sulfide, methane, and oxygen deficiency can be immediately dangerous, so the atmosphere must be tested for oxygen, flammables, and toxics and the space ventilated before and continuously during entry. An attendant, retrieval equipment, and a permit are required. Oxygen must be between 19.5 and 23.5 percent.29 CFR 1910.146

Before entry, a manhole 4 ft in diameter and 12 ft deep must be purged with 5 air changes. Using volume = 0.785 x diameter^2 x depth (about 151 ft^3), what total air volume must be moved to complete the purge?

• a.151 ft^3
• b.302 ft^3
• c.1,510 ft^3
• d.755 ft^3✓

Space volume = 0.785 x 4^2 x 12 = 0.785 x 16 x 12 = 151 ft^3, and 5 air changes require 5 x 151 = 755 ft^3 of air moved. Purging several air changes before entry clears hydrogen sulfide and methane and restores oxygen. The atmosphere is then re-tested in the order oxygen, flammable, toxic before anyone enters.29 CFR 1910.146

A plumber sets an extension ladder to reach a roof vent terminal. Using the 4-to-1 rule, how far should the base be from the wall if the ladder contacts the wall 16 ft up?

• a.4 ft✓
• b.2 ft
• c.8 ft
• d.16 ft

The 4-to-1 rule places the base 1 ft out for every 4 ft of working height, so 16 / 4 = 4 ft from the wall. This angle keeps the ladder from sliding out at the base or tipping back. The ladder should also extend at least 3 ft above the roof edge for a safe transition.29 CFR 1926.1053

Backflow prevention is a public-health safety requirement. What health event does a properly working backflow assembly prevent?

• a.Water hammer
• b.Contaminated water being drawn or pushed back into the potable supply✓
• c.Pipe corrosion
• d.Frozen pipes

Backflow protection prevents non-potable or contaminated water from entering the public drinking-water system through backsiphonage or backpressure, which has caused real disease outbreaks. The assembly is the barrier between a cross connection and the community's water. This is why high-hazard connections require the fail-safe reduced-pressure principle assembly.UPC §603.0

A master plumber must braze medical gas copper, which is hot work. What fire-safety precaution is required before starting?

• a.Only wear gloves
• b.Work faster to reduce exposure
• c.Obtain a hot-work permit, clear/cover combustibles, and post a fire watch with an extinguisher✓
• d.Open the gas valve to purge

Hot work such as brazing or soldering near combustibles requires a hot-work permit, removal or shielding of combustibles within the area, and a fire watch with an extinguisher during the work and for a period afterward. Sparks and heat can smolder in hidden materials and ignite after the crew leaves. This is standard for cutting, welding, and brazing.29 CFR 1926.352

A plumber replaces piping in a building constructed before 1978 and disturbs old painted surfaces and solder. What two legacy hazards require specific precautions?

• a.Asbestos and radon
• b.Silica and mold
• c.Formaldehyde and PCBs
• d.Lead (paint and old solder) and asbestos (pipe insulation and old sheet materials)✓

Pre-1978 buildings commonly contain lead paint and lead solder plus asbestos in pipe insulation, transite, and floor and sheet materials, both of which require specific handling, containment, and disposal rules. Lead solder was banned for potable use in 1986, and asbestos insulation must not be disturbed without proper controls. Both are serious long-term health hazards.EPA/OSHA lead

A 2,000 lb cast-iron section is lifted by a two-leg sling with each leg at 60 degrees from horizontal. Each leg carries (load / 2) / sin(60 degrees), with sin(60) about 0.866. What is the tension in each sling leg?

• a.1,155 lb✓
• b.1,000 lb
• c.1,414 lb
• d.2,000 lb

Each leg tension = (2,000 / 2) / 0.866 = 1,000 / 0.866 = 1,155 lb. As the sling angle drops toward horizontal, the leg tension climbs above the simple share of the load, which is why slings must be de-rated for angle. At a straight vertical lift each leg would carry only 1,000 lb.29 CFR 1926.251

During sewer confined-space work, the attendant outside must maintain what capability?

• a.Enter to help immediately without equipment
• b.Continuous communication with entrants and the ability to summon rescue without entering✓
• c.Leave to get tools as needed
• d.Perform the plumbing work

The attendant remains outside, keeps continuous communication with the entrants, monitors conditions, and summons trained rescue if needed, but does not enter the space to attempt rescue alone. Untrained would-be rescuers are a leading cause of confined-space fatalities. Non-entry retrieval systems allow rescue from outside.29 CFR 1910.146

A trench 10 ft deep in Type B soil is sloped at 1 to 1 (horizontal to vertical) on both sides. If the trench bottom is 3 ft wide, how wide is the excavation at the top?

• a.13 ft
• b.20 ft
• c.23 ft✓
• d.30 ft

Each side slopes back 1 x depth = 10 ft, so the top width = bottom + 2 x 10 = 3 + 20 = 23 ft. Type B soil requires a 1-to-1 slope, while less stable Type C requires 1.5 to 1 and would open even wider. The soil classification set by a competent person drives the excavation width and spoil space needed.29 CFR 1926.652

A trench 90 ft long and 6 ft deep requires egress so no worker travels more than 25 ft laterally to a ladder. A ladder placed mid-run protects 25 ft in each direction, or 50 ft total. What is the minimum number of ladders required?

• a.1 ladder
• b.3 ladders
• c.4 ladders
• d.2 ladders✓

Each ladder covers 50 ft of trench (25 ft of lateral travel on each side), so 90 ft / 50 ft = 1.8, which rounds up to 2 ladders. The 25 ft maximum travel ensures rapid exit if a wall fails or the atmosphere changes. Egress is required in any trench 4 ft or deeper and must extend above the top edge.29 CFR 1926.651

Before servicing a sewage ejector pump, the plumber must control hazardous energy. What procedure prevents the pump from starting during service?

• a.Lockout/tagout of the electrical disconnect, then verify zero energy✓
• b.Post a verbal warning
• c.Unplug only if convenient
• d.Work quickly between cycles

Lockout/tagout requires de-energizing the pump at its disconnect, applying a personal lock and tag, and verifying zero energy by attempting to start it before hands go near moving parts. An automatic float could start the pump unexpectedly and cause severe injury. Each worker applies their own lock.29 CFR 1910.147

On a California jobsite, a trench 5 ft or deeper in which workers will enter also requires a specific state permit beyond federal rules. What is that requirement?

• a.No permit is ever required in California
• b.A Cal/OSHA excavation/trench permit for trenches 5 ft or deeper that workers enter✓
• c.A federal permit only
• d.A permit only above 20 ft

Cal/OSHA requires a project or annual excavation permit for trenches 5 ft or more deep into which a person must descend, in addition to the cave-in protection rules. California often has requirements at least as strict as, and sometimes stricter than, federal OSHA. The competent person and daily inspections still apply.Cal/OSHA T8 1541

Cutting and grinding cast iron or concrete for a plumbing penetration generates respirable crystalline silica. What is the primary control the plumber should use?

• a.Work faster
• b.Open a window only
• c.Wet cutting or on-tool dust collection (engineering controls) plus respiratory protection as needed✓
• d.No control is needed for short tasks

The primary defense against respirable silica is engineering controls, using water (wet cutting) or a vacuum dust-collection shroud on the tool to suppress dust at the source, supplemented by respiratory protection when needed. Silica dust causes silicosis and is regulated with a strict exposure limit. Dry cutting without controls quickly exceeds the permissible exposure limit.29 CFR 1926.55