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Practice questions: site construction

Compiled by the Sitonce editorial team from the PSI Candidate Information Bulletin, NASCLA's own published material and the federal standards named belowUpdated 2 min readFacts verified 4 September 2026
The short answer

Site Construction is 15 of 115 scored questions. These four cover the protective system trigger, soil classification, spoil pile setback and an earthwork volume calculation.

Fifteen questions, and the soil table answers a good proportion of them.

Question 1

A trench is 4 feet 8 inches deep in Type B soil. Is a protective system required?

  1. Yes, any trench requires one
  2. No, the trigger is 5 feet
  3. Yes, because it is Type B soil
  4. Only if employees will enter it
Answer: B. The trigger is 5 feet, unless the excavation is entirely in stable rock. At 4 feet 8 inches no protective system is required by the depth rule, though egress and other provisions may still apply. Option D confuses this with the entry-based rules elsewhere.
Question 2

Soil at a site was excavated and backfilled two years ago and is now being reopened. How is it classified?

  1. By testing, as any other soil
  2. Type A if it tests at 1.5 tons per square foot
  3. Type C, because it has been previously disturbed
  4. Type B, as a default for backfill
Answer: C. Previously disturbed soil is Type C regardless of what it would otherwise test at. Option B is the trap - the strength test result does not override the disturbance rule.
Question 3

How far back from the edge of an excavation must spoil be placed?

  1. At least 2 feet
  2. At least 4 feet
  3. At least 6 feet
  4. Any distance, if sloped
Answer: A. 2 feet minimum, at 29 CFR 1926.651(j)(2). Option B is the depth at which egress requirements begin, offered here because 4 appears frequently in Subpart P.
Question 4

A slab measures 30 feet by 40 feet at 4 inches thick. How many cubic yards of concrete, before waste?

  1. About 14.8
  2. About 400
  3. About 44.4
  4. About 4.4
Answer: A. 30 times 40 times one third of a foot is 400 cubic feet. Divided by 27 gives about 14.8 cubic yards. Option B is the volume in cubic feet with the conversion forgotten, which is the classic error.

Two tables and one conversion

The soil table, the depth triggers, and 27 cubic feet to a cubic yard. Between them they cover most of this category.

Common questions

When is a protective system required?

At 5 feet deep, unless the excavation is entirely in stable rock.

How is previously disturbed soil classified?

Type C, regardless of what it would otherwise test at.

How far back must spoil be placed?

At least 2 feet from the edge.

How do I calculate concrete volume?

Length times width times thickness in feet, then divide by 27 for cubic yards.

What covers most of this category?

The soil classification table, the depth triggers, and the cubic feet to cubic yards conversion.

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