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New Mexico (MS-3) Cesspools, Septic Tanks & Sewers
Exam | Latest Verified Questions and Detailed Answers
OVERVIEW DESCRIPTION:
The New Mexico MS-3 (Cesspools, Septic Tanks & Sewers) exam is a specialized trade
test required for contractors seeking certification to install, maintain, and repair onsite
liquid waste systems. Administered by PSI Testing Services on behalf of the New Mexico
Environment Department (NMED), the exam ensures a comprehensive understanding of
state-specific regulations, particularly NMAC 20.7.3. Key topics covered include proper
site evaluation and soil analysis, the design and sizing of conventional and alternative
systems (like septic tanks, drain fields, and aerobic units), and critical safety protocols for
trenching and confined space entry. The test also assesses knowledge of proper
installation materials, troubleshooting system failures, and adhering to permitting and
inspection processes to protect public health and New Mexico's groundwater resources.
QUESTION 1
Which New Mexico Administrative Code (NMAC) section is the primary regulation
governing the design, construction, and abandonment of on-site liquid waste systems?
A) NMAC 20.6.1
B) NMAC 20.7.3
C) NMAC 21.2.5
D) NMAC 19.4.2
CORRECT ANSWER: B
EXPERT RATIONALE: NMAC 20.7.3 is the specific regulation that sets all standards for
on-site liquid waste disposal systems in New Mexico, ensuring public health and
environmental protection .
QUESTION 2
What is the maximum daily flow threshold for a domestic wastewater system to be
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regulated by the NMED liquid waste program, rather than requiring a full groundwater
discharge permit?
A) 1,000 gallons per day
B) 2,500 gallons per day
C) 5,000 gallons per day
D) 10,000 gallons per day
CORRECT ANSWER: C
EXPERT RATIONALE: Discharges to a septic system less than 5,000 gallons per day are
regulated by the NMED liquid waste program; discharges greater than that require a
discharge permit .
QUESTION 3
When a public sewer becomes available to a property with an existing septic system,
how many days does the owner have to connect to the public sewer and abandon the
on-site system?
A) 10 days
B) 30 days
C) 60 days
D) 90 days
CORRECT ANSWER: B
EXPERT RATIONALE: New Mexico law mandates that the owner must abandon the on-
site system and connect to the public sewer within 30 days of its availability to ensure
public health and proper waste management .
QUESTION 4
What is the minimum design flow rate per bedroom used to calculate the required size
for a residential septic system in New Mexico?
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A) 100 GPD
B) 120 GPD
C) 150 GPD
D) 200 GPD
CORRECT ANSWER: C
EXPERT RATIONALE: Residential design flow is calculated at 150 gallons per day (GPD)
per bedroom as the baseline for sizing a septic system, though it may be adjusted to the
next increment .
QUESTION 5
A licensed contractor holding which of the following licenses is qualified to install septic
systems in New Mexico?
A) MM-1 only
B) MS-3 only
C) GB-98
D) MM-1, MM-98, MS-1, or MS-3
CORRECT ANSWER: D
EXPERT RATIONALE: Contractors with a valid MM-1, MM-98, MS-1, or MS-3 license are
all qualified by the NMED to install septic systems in the state .
QUESTION 6
According to NMAC 20.7.3, what is the minimum setback distance required between a
new septic tank and a private potable water well?
A) 25 feet
B) 50 feet
C) 75 feet
D) 100 feet
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CORRECT ANSWER: B
EXPERT RATIONALE: NMAC 20.7.3 requires a minimum separation of 50 feet between
any on-site wastewater treatment component and a private drinking-water well to
prevent contamination .
QUESTION 7
What is the primary function of anaerobic bacteria in a septic tank?
A) To oxidize organic matter into carbon dioxide
B) To convert ammonia into nitrate
C) To break down solids into sludge and scum in an oxygen-free environment
D) To filter pathogens from the liquid effluent
CORRECT ANSWER: C
EXPERT RATIONALE: Anaerobic bacteria thrive in the oxygen-free environment of the
septic tank, where they decompose organic solids, allowing them to settle as sludge or
float as scum .
QUESTION 8
Which soil test is most commonly used in New Mexico to determine the absorption rate
of soil for a septic drain field?
A) pH Test
B) Compaction Test
C) Atterberg Limits Test
D) Percolation Test
CORRECT ANSWER: D
EXPERT RATIONALE: A percolation (perc) test measures the rate at which water absorbs
into the soil, which is critical for designing a drain field that can effectively handle
wastewater .
New Mexico (MS-3) Cesspools, Septic Tanks & Sewers
Exam | Latest Verified Questions and Detailed Answers
OVERVIEW DESCRIPTION:
The New Mexico MS-3 (Cesspools, Septic Tanks & Sewers) exam is a specialized trade
test required for contractors seeking certification to install, maintain, and repair onsite
liquid waste systems. Administered by PSI Testing Services on behalf of the New Mexico
Environment Department (NMED), the exam ensures a comprehensive understanding of
state-specific regulations, particularly NMAC 20.7.3. Key topics covered include proper
site evaluation and soil analysis, the design and sizing of conventional and alternative
systems (like septic tanks, drain fields, and aerobic units), and critical safety protocols for
trenching and confined space entry. The test also assesses knowledge of proper
installation materials, troubleshooting system failures, and adhering to permitting and
inspection processes to protect public health and New Mexico's groundwater resources.
QUESTION 1
Which New Mexico Administrative Code (NMAC) section is the primary regulation
governing the design, construction, and abandonment of on-site liquid waste systems?
A) NMAC 20.6.1
B) NMAC 20.7.3
C) NMAC 21.2.5
D) NMAC 19.4.2
CORRECT ANSWER: B
EXPERT RATIONALE: NMAC 20.7.3 is the specific regulation that sets all standards for
on-site liquid waste disposal systems in New Mexico, ensuring public health and
environmental protection .
QUESTION 2
What is the maximum daily flow threshold for a domestic wastewater system to be
,2|Page
regulated by the NMED liquid waste program, rather than requiring a full groundwater
discharge permit?
A) 1,000 gallons per day
B) 2,500 gallons per day
C) 5,000 gallons per day
D) 10,000 gallons per day
CORRECT ANSWER: C
EXPERT RATIONALE: Discharges to a septic system less than 5,000 gallons per day are
regulated by the NMED liquid waste program; discharges greater than that require a
discharge permit .
QUESTION 3
When a public sewer becomes available to a property with an existing septic system,
how many days does the owner have to connect to the public sewer and abandon the
on-site system?
A) 10 days
B) 30 days
C) 60 days
D) 90 days
CORRECT ANSWER: B
EXPERT RATIONALE: New Mexico law mandates that the owner must abandon the on-
site system and connect to the public sewer within 30 days of its availability to ensure
public health and proper waste management .
QUESTION 4
What is the minimum design flow rate per bedroom used to calculate the required size
for a residential septic system in New Mexico?
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A) 100 GPD
B) 120 GPD
C) 150 GPD
D) 200 GPD
CORRECT ANSWER: C
EXPERT RATIONALE: Residential design flow is calculated at 150 gallons per day (GPD)
per bedroom as the baseline for sizing a septic system, though it may be adjusted to the
next increment .
QUESTION 5
A licensed contractor holding which of the following licenses is qualified to install septic
systems in New Mexico?
A) MM-1 only
B) MS-3 only
C) GB-98
D) MM-1, MM-98, MS-1, or MS-3
CORRECT ANSWER: D
EXPERT RATIONALE: Contractors with a valid MM-1, MM-98, MS-1, or MS-3 license are
all qualified by the NMED to install septic systems in the state .
QUESTION 6
According to NMAC 20.7.3, what is the minimum setback distance required between a
new septic tank and a private potable water well?
A) 25 feet
B) 50 feet
C) 75 feet
D) 100 feet
, 4|Page
CORRECT ANSWER: B
EXPERT RATIONALE: NMAC 20.7.3 requires a minimum separation of 50 feet between
any on-site wastewater treatment component and a private drinking-water well to
prevent contamination .
QUESTION 7
What is the primary function of anaerobic bacteria in a septic tank?
A) To oxidize organic matter into carbon dioxide
B) To convert ammonia into nitrate
C) To break down solids into sludge and scum in an oxygen-free environment
D) To filter pathogens from the liquid effluent
CORRECT ANSWER: C
EXPERT RATIONALE: Anaerobic bacteria thrive in the oxygen-free environment of the
septic tank, where they decompose organic solids, allowing them to settle as sludge or
float as scum .
QUESTION 8
Which soil test is most commonly used in New Mexico to determine the absorption rate
of soil for a septic drain field?
A) pH Test
B) Compaction Test
C) Atterberg Limits Test
D) Percolation Test
CORRECT ANSWER: D
EXPERT RATIONALE: A percolation (perc) test measures the rate at which water absorbs
into the soil, which is critical for designing a drain field that can effectively handle
wastewater .
