NM GF-9 Utility Lines Latest Practice Exam
(Updated Edition)
1.
A contractor is installing an 8-inch PVC gravity sewer line at a depth of 7 feet in Type C soil. No
groundwater is present. What OSHA-compliant protective system is MOST appropriate?
A. Vertical trench walls with spot bracing
B. Sloping at 1½:1 or using a trench shield
C. Benching with 1:1 horizontal to vertical ratio
D. No protection required if entry time is limited
Correct Answer: B
Explanation: OSHA requires protection for trenches 5 feet or deeper unless in stable rock. Type C
soil requires 1½:1 slope or a shield system. Vertical walls are prohibited.
2.
Before excavating for a natural gas service line in New Mexico, a utility contractor must notify the
One Call system how many working days in advance, excluding weekends and holidays?
A. 24 hours
B. 48 hours
C. 2 full working days
D. 5 calendar days
Correct Answer: C
Explanation: New Mexico law requires notification to NM One Call (811) at least two working
days before excavation, excluding weekends and holidays.
3.
During trench excavation, a competent person observes tension cracks forming 18 inches from the
trench edge. What is the MOST appropriate immediate action?
A. Continue work but increase inspection frequency
B. Install a ladder within 25 feet of workers
C. Stop work and re-slope or shore the trench
D. Reduce equipment movement near the edge
Correct Answer: C
Explanation: Tension cracks indicate imminent trench failure. OSHA requires immediate corrective
action, including re-sloping or shoring before work resumes.
4.
, NM GF-9 Utility Lines Latest Practice Exam
(Updated Edition)
When installing ductile iron water main using push-on joints, which condition is MOST critical to
ensure joint integrity?
A. Over-tightening the joint gasket
B. Proper cleaning and lubrication of the gasket
C. Backfilling before pressure testing
D. Installing thrust blocks after hydrostatic testing
Correct Answer: B
Explanation: Push-on joints rely on clean, lubricated gaskets for proper seating and sealing.
Improper preparation leads to leaks or joint failure.
5.
What is the PRIMARY reason for installing a granular bedding beneath underground utility piping?
A. Increase pipe weight
B. Prevent corrosion
C. Provide uniform load support and alignment
D. Improve soil electrical conductivity
Correct Answer: C
Explanation: Proper bedding ensures even load distribution, reduces point loading, and
maintains pipe grade and alignment, especially for gravity systems.
6.
A sewer trench is excavated to 9 feet, and a trench box is used. Workers must install pipe at the
bottom. What OSHA requirement applies?
A. The trench box must extend to trench bottom
B. The box must extend at least 18 inches above the trench
C. Workers may exit the box briefly if wearing PPE
D. Sloping is still required behind the box
Correct Answer: A
Explanation: Trench boxes must protect workers fully, extending to the bottom where employees
are working. Gaps at the bottom are not permitted.
7.
Which soil classification has the LOWEST unconfined compressive strength?
A. Type A
B. Type B
, NM GF-9 Utility Lines Latest Practice Exam
(Updated Edition)
C. Type C
D. Stable rock
Correct Answer: C
Explanation: Type C soil (sand, gravel, submerged soil) has the lowest stability and highest cave-in
risk, requiring the most conservative protection methods.
8.
For a gravity sewer line, what is the PRIMARY purpose of maintaining minimum slope requirements?
A. Reduce trench depth
B. Prevent infiltration
C. Maintain self-cleaning velocity
D. Increase pipe lifespan
Correct Answer: C
Explanation: Proper slope ensures adequate flow velocity to prevent solids from settling and
clogging the sewer line.
9.
A contractor damages an underground fiber optic line after failing to pothole a marked location.
Under NM law, which consequence is MOST likely?
A. Automatic license revocation
B. No penalty if damage was accidental
C. Liability for repair costs and potential civil penalties
D. Only a written warning
Correct Answer: C
Explanation: Failure to follow damage prevention procedures, including potholing, can result
in repair liability, fines, and enforcement action.
10.
Which method is BEST for locating existing underground utilities at marked locations before
mechanical excavation?
A. Tracer wire testing
B. Ground-penetrating radar only
C. Vacuum excavation (potholing)
D. Magnetic detection
, NM GF-9 Utility Lines Latest Practice Exam
(Updated Edition)
Correct Answer: C
Explanation: Vacuum excavation is the safest and most accurate method to visually confirm utility
depth and alignment.
11.
What is the MOST critical safety concern when excavating near an existing gas main?
A. Soil compaction requirements
B. Utility color code compliance
C. Potential ignition from mechanical equipment
D. Pipe bedding material
Correct Answer: C
Explanation: Striking or stressing a gas line can cause leaks and explosions, especially if ignition
sources are present.
12.
When pressure testing a newly installed water main, testing should be performed:
A. After final paving
B. Before backfilling
C. After partial backfill with joints exposed
D. Only after service connections are activated
Correct Answer: C
Explanation: Pressure testing is done before final backfill, with joints exposed, to identify leaks
without requiring re-excavation.
13.
Which backfill practice is MOST appropriate for utility trenches under paved roadways?
A. Native soil dumped in lifts
B. Flowable fill or compacted granular material
C. Loose sand only
D. Uncompacted soil with surface asphalt
Correct Answer: B
Explanation: Roadways require controlled compaction or flowable fill to prevent settlement and
pavement failure.
14.
(Updated Edition)
1.
A contractor is installing an 8-inch PVC gravity sewer line at a depth of 7 feet in Type C soil. No
groundwater is present. What OSHA-compliant protective system is MOST appropriate?
A. Vertical trench walls with spot bracing
B. Sloping at 1½:1 or using a trench shield
C. Benching with 1:1 horizontal to vertical ratio
D. No protection required if entry time is limited
Correct Answer: B
Explanation: OSHA requires protection for trenches 5 feet or deeper unless in stable rock. Type C
soil requires 1½:1 slope or a shield system. Vertical walls are prohibited.
2.
Before excavating for a natural gas service line in New Mexico, a utility contractor must notify the
One Call system how many working days in advance, excluding weekends and holidays?
A. 24 hours
B. 48 hours
C. 2 full working days
D. 5 calendar days
Correct Answer: C
Explanation: New Mexico law requires notification to NM One Call (811) at least two working
days before excavation, excluding weekends and holidays.
3.
During trench excavation, a competent person observes tension cracks forming 18 inches from the
trench edge. What is the MOST appropriate immediate action?
A. Continue work but increase inspection frequency
B. Install a ladder within 25 feet of workers
C. Stop work and re-slope or shore the trench
D. Reduce equipment movement near the edge
Correct Answer: C
Explanation: Tension cracks indicate imminent trench failure. OSHA requires immediate corrective
action, including re-sloping or shoring before work resumes.
4.
, NM GF-9 Utility Lines Latest Practice Exam
(Updated Edition)
When installing ductile iron water main using push-on joints, which condition is MOST critical to
ensure joint integrity?
A. Over-tightening the joint gasket
B. Proper cleaning and lubrication of the gasket
C. Backfilling before pressure testing
D. Installing thrust blocks after hydrostatic testing
Correct Answer: B
Explanation: Push-on joints rely on clean, lubricated gaskets for proper seating and sealing.
Improper preparation leads to leaks or joint failure.
5.
What is the PRIMARY reason for installing a granular bedding beneath underground utility piping?
A. Increase pipe weight
B. Prevent corrosion
C. Provide uniform load support and alignment
D. Improve soil electrical conductivity
Correct Answer: C
Explanation: Proper bedding ensures even load distribution, reduces point loading, and
maintains pipe grade and alignment, especially for gravity systems.
6.
A sewer trench is excavated to 9 feet, and a trench box is used. Workers must install pipe at the
bottom. What OSHA requirement applies?
A. The trench box must extend to trench bottom
B. The box must extend at least 18 inches above the trench
C. Workers may exit the box briefly if wearing PPE
D. Sloping is still required behind the box
Correct Answer: A
Explanation: Trench boxes must protect workers fully, extending to the bottom where employees
are working. Gaps at the bottom are not permitted.
7.
Which soil classification has the LOWEST unconfined compressive strength?
A. Type A
B. Type B
, NM GF-9 Utility Lines Latest Practice Exam
(Updated Edition)
C. Type C
D. Stable rock
Correct Answer: C
Explanation: Type C soil (sand, gravel, submerged soil) has the lowest stability and highest cave-in
risk, requiring the most conservative protection methods.
8.
For a gravity sewer line, what is the PRIMARY purpose of maintaining minimum slope requirements?
A. Reduce trench depth
B. Prevent infiltration
C. Maintain self-cleaning velocity
D. Increase pipe lifespan
Correct Answer: C
Explanation: Proper slope ensures adequate flow velocity to prevent solids from settling and
clogging the sewer line.
9.
A contractor damages an underground fiber optic line after failing to pothole a marked location.
Under NM law, which consequence is MOST likely?
A. Automatic license revocation
B. No penalty if damage was accidental
C. Liability for repair costs and potential civil penalties
D. Only a written warning
Correct Answer: C
Explanation: Failure to follow damage prevention procedures, including potholing, can result
in repair liability, fines, and enforcement action.
10.
Which method is BEST for locating existing underground utilities at marked locations before
mechanical excavation?
A. Tracer wire testing
B. Ground-penetrating radar only
C. Vacuum excavation (potholing)
D. Magnetic detection
, NM GF-9 Utility Lines Latest Practice Exam
(Updated Edition)
Correct Answer: C
Explanation: Vacuum excavation is the safest and most accurate method to visually confirm utility
depth and alignment.
11.
What is the MOST critical safety concern when excavating near an existing gas main?
A. Soil compaction requirements
B. Utility color code compliance
C. Potential ignition from mechanical equipment
D. Pipe bedding material
Correct Answer: C
Explanation: Striking or stressing a gas line can cause leaks and explosions, especially if ignition
sources are present.
12.
When pressure testing a newly installed water main, testing should be performed:
A. After final paving
B. Before backfilling
C. After partial backfill with joints exposed
D. Only after service connections are activated
Correct Answer: C
Explanation: Pressure testing is done before final backfill, with joints exposed, to identify leaks
without requiring re-excavation.
13.
Which backfill practice is MOST appropriate for utility trenches under paved roadways?
A. Native soil dumped in lifts
B. Flowable fill or compacted granular material
C. Loose sand only
D. Uncompacted soil with surface asphalt
Correct Answer: B
Explanation: Roadways require controlled compaction or flowable fill to prevent settlement and
pavement failure.
14.
