Question 1

At what depth must a protective system be used in an excavation?

Accepted Answer

Excavations 5 feet or deeper require a protective system (sloping, shoring, or shielding) unless the excavation is made entirely in stable rock.

Question 2

How far from the edge of an excavation must spoil (excavated material) be kept?

Accepted Answer

Spoil must be kept at least 2 feet from the edge of the excavation to prevent it from falling back into the trench and to reduce surcharge loading.

Question 3

In a trench excavation, a means of egress (ladder, steps, or ramp) must be provided within how many feet of lateral travel for employees?

Accepted Answer

A stairway, ladder, ramp, or other safe means of egress shall be located in trench excavations that are 4 feet or deeper so as to require no more than 25 feet of lateral travel for employees.

Question 4

Who must inspect excavations daily and before the start of each shift?

Accepted Answer

Daily inspections of excavations, the adjacent areas, and protective systems shall be made by a competent person for evidence of possible cave-ins, failures of protective systems, or hazardous atmospheres.

Question 5

Type A soil has an unconfined compressive strength of:

Accepted Answer

Type A soil is cohesive soil with an unconfined compressive strength of 1.5 tons per square foot (tsf) or greater. Examples include clay, silty clay, and hardpan.

Question 6

Type B soil has an unconfined compressive strength of:

Accepted Answer

Type B soil is cohesive soil with an unconfined compressive strength greater than 0.5 tsf but less than 1.5 tsf. Examples include angular gravel, silt, and silt loam.

Question 7

Type C soil has an unconfined compressive strength of:

Accepted Answer

Type C soil is cohesive soil with an unconfined compressive strength of 0.5 tsf or less. Examples include gravel, sand, loamy sand, and submerged soil.

Question 8

What is the maximum allowable slope for Type C soil?

Accepted Answer

Type C soil has a maximum allowable slope of 1-1/2 horizontal to 1 vertical (34 degrees). This is the least stable soil type and requires the gentlest slope.

Question 9

What is the maximum allowable slope for Type A soil?

Accepted Answer

Type A soil has a maximum allowable slope of 3/4 horizontal to 1 vertical (53 degrees). This is the most stable soil type.

Question 10

At what depth must excavation protective systems be designed by a registered professional engineer?

Accepted Answer

Excavations deeper than 20 feet require that the protective system be designed by a registered professional engineer.

Question 11

Which of the following is a Type C soil?

Accepted Answer

Type C soils include granular soils such as gravel, sand, and loamy sand; submerged soil; soil from which water is freely seeping; and submerged rock that is not stable.

Question 12

Before an excavation is started near underground utilities, the employer must:

Accepted Answer

The estimated location of utility installations shall be determined by contacting the local utility companies or the state one-call system (811) before excavation begins.

Question 13

A trench box (trench shield) provides protection by:

Accepted Answer

A trench box or trench shield is designed to protect workers by shielding them from cave-in material. It does not prevent cave-ins; rather, it protects workers if soil collapses.

Question 14

When testing for atmospheric hazards in an excavation, what should be tested first?

Accepted Answer

Oxygen levels should be tested first because both oxygen-deficient and oxygen-enriched atmospheres are immediately dangerous. Normal oxygen is 19.5% to 23.5%.

Question 15

What is the maximum allowable slope for Type B soil?

Accepted Answer

Type B soil has a maximum allowable slope of 1 horizontal to 1 vertical (45 degrees).

Question 16

Which of the following methods of excavation protection involves cutting back the walls of the excavation to form an incline?

Accepted Answer

Sloping involves cutting back the trench wall at an angle inclined away from the excavation. The angle depends on the soil type.

Question 17

Benching is NOT permitted in which type of soil?

Accepted Answer

Benching is not permitted in Type C soil because it is too unstable. Benching is only allowed in Type A and Type B soils.

Question 18

What is the definition of a 'competent person' in excavation work?

Accepted Answer

A competent person is one who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures.

Question 19

When must excavation inspections be conducted after rain?

Accepted Answer

Inspections shall be made after every rainstorm or other hazard-increasing occurrence. These inspections are conducted by a competent person before employees are permitted to re-enter the excavation.

Question 20

Workers in excavations must be protected from cave-ins by a protective system unless the excavation is:

Accepted Answer

Protective systems are not required when excavations are made entirely in stable rock, or are less than 5 feet deep and examination by a competent person provides no indication of a potential cave-in.

Question 21

What is the primary hazard associated with excavations?

Accepted Answer

Cave-ins are the primary hazard in excavation work and pose the greatest risk to workers. Cave-ins can be sudden and fatal.

Question 22

Shoring is a method of excavation protection that involves:

Accepted Answer

Shoring is a structure such as a metal hydraulic, mechanical, or timber system that supports the sides of an excavation and is designed to prevent cave-ins.

Question 23

When approaching utility lines during excavation, hand digging must begin within what distance of the estimated location?

Accepted Answer

When excavation operations approach the estimated location of underground installations, the exact location must be determined by safe and acceptable means. Hand digging or equivalent must be used within the tolerance zone as determined by state law or utility requirements.

Question 24

A trench is defined as a narrow excavation where the depth is greater than the width, and the width does not exceed:

Accepted Answer

A trench is a narrow excavation (in relation to its length) made below the surface of the ground. In general, the depth is greater than the width, but the width of a trench is not greater than 15 feet.

Question 25

When employees or equipment are permitted to cross over excavations, what must be provided?

Accepted Answer

Walkways or bridges shall be provided where employees or equipment are required or permitted to cross over excavations. Guardrails shall be provided where walkways or bridges are 6 feet or more above lower levels.

Question 26

What soil testing method uses a device that measures the unconfined compressive strength of a soil sample?

Accepted Answer

A pocket penetrometer is a direct-reading, spring-operated instrument used to measure the approximate unconfined compressive strength of saturated cohesive soils.

Question 27

Excavations adjacent to structures or foundations may require special precautions. What must be done to protect the stability of adjoining structures?

Accepted Answer

Where the stability of adjoining buildings, walls, or other structures is endangered by excavation operations, support systems such as shoring, bracing, or underpinning shall be provided.

Question 28

What is the purpose of water removal equipment in an excavation?

Accepted Answer

Water accumulation in excavations must be controlled. If water removal equipment is used, a competent person must monitor conditions, as water can undermine excavation walls and create hazards.

Question 29

The three types of protective systems for excavations are:

Accepted Answer

The three types of protective systems for excavations are: sloping and benching (cutting back the walls), shoring (supporting the walls), and shielding (using trench boxes).

Question 30

If a previously classified soil type shows signs of distress (such as tension cracks), what action must the competent person take?

Accepted Answer

If, after classifying a deposit, the competent person finds indications of distress such as tension cracks, the soil must be reclassified to a less stable type and protective measures must be increased.

Question 31

Excavation warning systems for vehicular traffic must include which of the following?

Accepted Answer

Where mobile equipment is operated adjacent to an excavation, warning systems such as barricades, hand or mechanical signals, or stop logs shall be used to prevent equipment from falling into the excavation.

Question 32

In what type of soil are vertical cuts up to 12 feet permitted in a short-term exposure?

Accepted Answer

In Type A soil, short-term simple slope excavations up to 12 feet deep may have maximum allowable slopes of 1/2 horizontal to 1 vertical. However, this is only for short-term conditions.

Question 33

What must be done with utilities discovered during excavation?

Accepted Answer

Underground installations that are exposed must be protected, supported, or removed as necessary to safeguard employees.

Question 34

A competent person performing a visual test of soil should look for all of the following EXCEPT:

Accepted Answer

Visual tests include observation of particle size, evidence of water, cracks or fissures, spalling, layering, and previously disturbed soil. Soil color alone is not a reliable indicator of soil type.

Question 35

The OSHA standard for excavations in construction is found in:

Accepted Answer

Subpart P of 29 CFR 1926 covers excavation requirements for construction, including sections 1926.650 through 1926.652 and associated appendices.

Question 36

An oxygen-deficient atmosphere in an excavation is one that contains less than:

Accepted Answer

An oxygen-deficient atmosphere contains less than 19.5% oxygen. Normal atmospheric oxygen is approximately 20.9%. Below 19.5% is considered immediately dangerous.

Question 37

When is atmospheric testing required in an excavation?

Accepted Answer

Where oxygen deficiency or a hazardous atmosphere exists or could reasonably be expected to exist, the atmospheres in the excavation shall be tested before employees enter.

Question 38

What is a surcharge load in excavation safety?

Accepted Answer

Surcharge loads are loads placed close to the edge of an excavation, such as heavy equipment, materials, or spoil piles, that increase the pressure on the excavation walls and can contribute to cave-ins.

Question 39

What is the minimum distance that heavy equipment or vehicles must be kept from the edge of an excavation?

Accepted Answer

OSHA does not specify an exact minimum distance. The competent person must determine a safe distance based on soil conditions, the weight of the equipment, and other factors to prevent cave-in.

Question 40

When using a trench box (shield), the shield must extend at least how far above the surrounding area if there is no sloping?

Accepted Answer

Shields must extend at least 18 inches above the top of the vertical side when used in conditions where there is no sloping of the adjoining ground.

Question 41

Employees are permitted to enter bell-bottom pier holes and similar deep and confined footing excavations only when:

Accepted Answer

Employees shall be protected from cave-ins in bell-bottom pier holes and similar excavations by means of casing or other approved methods.

Question 42

The competent person for an excavation must perform inspections:

Accepted Answer

Inspections shall be made by a competent person daily, prior to the start of work, and as needed throughout each shift. Additional inspections are required after rainstorms or other events.

Question 43

One cubic yard of soil weighs approximately:

Accepted Answer

One cubic yard of soil typically weighs approximately 3,000 pounds (1.5 tons), which is why cave-ins are so dangerous and often fatal.

Question 44

What method of soil testing involves molding soil into a thin ribbon by squeezing between the thumb and fingers?

Accepted Answer

The ribbon test involves molding a moist soil sample into a ribbon by squeezing between the thumb and fingers. The length and behavior of the ribbon helps classify the soil type.

Question 45

Employees in an excavation where a hazardous atmosphere could exist must be provided with:

Accepted Answer

Where hazardous atmospheres could exist, emergency rescue equipment such as breathing apparatus, safety harness and line, and a basket stretcher shall be readily available.

Question 46

What is the primary purpose of a trench shield (trench box)?

Accepted Answer

A trench shield (trench box) is designed to protect workers inside the trench by shielding them from soil that may collapse. It does not prevent cave-ins from occurring; rather, it deflects the caving soil away from workers. Workers must remain within the protected area of the shield at all times.

Question 47

When a trench shield is being installed or removed, employees may be in the trench:

Accepted Answer

Employees shall be protected from cave-ins when entering or exiting the trench shield area. Workers are permitted in the trench during shield installation or removal only when they are within the protection of the shield or another adequate protective system.

Question 48

Which soil classification method involves a device that measures shear strength by inserting a vane into the soil and rotating it?

Accepted Answer

A torvane (shear vane) is a hand-held instrument used to measure the shear strength of cohesive soil. The vane is inserted into the soil and rotated until the soil shears, providing a reading that helps classify the soil type. It is one of several manual testing methods used by competent persons.

Question 49

Surface encumbrances near an excavation include which of the following?

Accepted Answer

All surface encumbrances that are located so as to create a hazard to employees shall be removed or supported, as necessary, to safeguard employees. Surface encumbrances include trees, utility poles, sidewalks, pavement, boulders, fences, and any other above-ground objects that could fall into or destabilize the excavation.

Question 50

When must the employer contact utility companies before beginning excavation?

Accepted Answer

The estimated location of utility installations shall be determined by contacting the local utility companies or one-call system prior to opening an excavation. The employer must allow sufficient time for the utilities to respond and mark or locate their lines before digging begins.

Question 51

The thumb penetration test for soil classification involves pressing the thumb into a soil sample. If the thumb penetrates the full length with moderate effort, the soil is likely:

Accepted Answer

In the thumb penetration test, if the thumb penetrates the soil sample with moderate effort, the soil is generally classified as Type B. If the thumb barely penetrates, the soil may be Type A. If the thumb penetrates easily, the soil is likely Type C. This is a manual field test and should be supplemented with other testing methods.

Question 52

Tabulated data used for the design of shoring systems in excavations must be:

Accepted Answer

Tabulated data used to design and construct a shoring system must be in written form and include all criteria necessary for determining the protection to be provided. The data must identify the registered professional engineer who approved it and specify the limits of application.

Question 53

In an excavation where water is accumulating, what must the competent person do?

Accepted Answer

The competent person must monitor and control water accumulation hazards. If water removal equipment is used, conditions must be monitored by a competent person to ensure safe operations. Employees shall not work in excavations with accumulated water unless adequate protections are in place.

Question 54

What is the minimum distance that a ladder must extend above the top of a trench when used as a means of egress?

Accepted Answer

When a ladder is used as a means of egress from a trench, it must extend at least 3 feet above the top of the trench to provide a secure handhold for employees climbing out. This applies to trenches 4 feet or deeper.

Question 55

A competent person is evaluating an excavation and observes water seeping through the wall and fissured soil with evidence of previous disturbance. What soil classification should be applied?

Accepted Answer

Soil from which water is freely seeping and previously disturbed soil (unless the competent person determines it to be Type A or B) are both classified as Type C. These conditions indicate low cohesive strength and high instability. The most protective classification must be used when multiple factors are present.

Question 56

What is 'stable rock' as defined in OSHA's excavation standard?

Accepted Answer

Stable rock is defined as natural solid mineral material that can be excavated with vertical sides and will remain intact while exposed. Excavations in stable rock do not require sloping or shoring, as the rock is self-supporting.

Question 57

Hydraulic shoring systems provide protection by:

Accepted Answer

Hydraulic shoring systems use hydraulic cylinders (pistons) placed between the trench walls to exert outward pressure. This bracing action prevents the trench walls from collapsing inward. Hydraulic shoring is a type of support system that actively resists soil movement.

Question 58

For excavations deeper than 20 feet, OSHA requires that protective systems be designed by:

Accepted Answer

For excavations deeper than 20 feet, a registered professional engineer must design the protective system. The engineer must consider all relevant factors including soil conditions, depth, surcharge loads, and groundwater to ensure the design provides adequate worker protection.

Question 59

When working near an excavation that could affect the stability of an adjacent building foundation, what is the employer's first obligation?

Accepted Answer

Where the stability of adjoining buildings, walls, or other structures is endangered by excavation operations, support systems such as shoring, bracing, or underpinning shall be provided to ensure the stability of the structure. This must be done before conditions become unsafe.

Question 60

What test method provides the most precise measurement of soil unconfined compressive strength in the field?

Accepted Answer

A pocket penetrometer is a direct-reading, spring-operated instrument that provides the most precise field measurement of unconfined compressive strength for cohesive soils. While visual and manual tests are useful, the pocket penetrometer gives a numerical value that can be directly compared to soil classification thresholds.

Question 61

Emergency rescue equipment for excavations with hazardous atmospheres must include:

Accepted Answer

When hazardous atmospheres could exist in an excavation, emergency rescue equipment must be readily available and include breathing apparatus, a safety harness and lifeline, and a basket stretcher. Attendants must be available to provide emergency assistance, and employees must not enter until the atmosphere has been tested.

Question 62

Which of the following is NOT classified as Type A soil even if its unconfined compressive strength is 1.5 tsf or greater?

Accepted Answer

Even if a soil has an unconfined compressive strength of 1.5 tsf or greater, it cannot be classified as Type A if it is fissured, subject to vibration from heavy traffic, pile driving, or similar effects, previously disturbed, or part of a sloped or layered system where the layers dip toward the excavation on a slope of 4H:1V or steeper.

Question 63

When digging near an existing underground gas line, what precaution must be taken once the approximate location is known?

Accepted Answer

When excavation operations approach the estimated location of underground installations, the exact location shall be determined by safe and acceptable means, such as hand digging or soft digging techniques. This prevents accidental damage to utilities, which could result in explosions, electrocution, flooding, or toxic exposure.

Question 64

A support system for an excavation must be installed:

Accepted Answer

Support systems (such as shoring) must be installed from the top down and removed from the bottom up. This installation sequence ensures workers are protected at all times during the process, as the upper sections provide support while lower sections are being installed or after lower sections have been removed.

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