APWA CERTIFIED STORMWATER MANAGER (CSM) EXAM QUESTIONS AND CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2026 Q&A | LATEST EXAM UPDATE 2026/2027
SECTION ONE: QUESTIONS 1-100
1. A stormwater manager is evaluating a proposed residential development that will convert 15 acres of
forest to impervious surfaces. What should be the primary concern regarding the receiving stream?
A. Increased base flow during dry weather
B. Decreased peak flow rates due to faster runoff
C. Increased runoff volume and peak flow rates causing channel erosion
D. Lower pollutant concentrations due to reduced infiltration
🟢 C. Increased runoff volume and peak flow rates causing channel erosion
🔴 RATIONALE: Converting pervious surfaces to impervious cover increases runoff volume and peak flow rates,
which can cause channel erosion, habitat degradation, and downstream flooding. Base flow would typically
decrease due to reduced infiltration, not increase .
2. The Clean Water Act (CWA) of 1972 provides the primary regulatory framework for regulating stormwater
discharges. Which of the following is a critical component of the CWA that regulates stormwater discharges
from construction activities?
A. Safe Drinking Water Act (SDWA)
B. Resource Conservation and Recovery Act (RCRA)
C. National Pollutant Discharge Elimination System (NPDES) permit program
D. Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)
,🟢 C. National Pollutant Discharge Elimination System (NPDES) permit program
🔴 RATIONALE: The NPDES permit program, authorized by Section 402 of the Clean Water Act, regulates the
discharge of pollutants from point sources, including stormwater from construction activities and municipal
separate storm sewer systems .
3. Which of the following is the best definition of a Total Maximum Daily Load (TMDL)?
A. The maximum amount of a pollutant that a waterbody can receive while still meeting water quality standards
B. The minimum daily flow required to maintain navigation in a river
C. The total volume of stormwater that can be discharged from a site without a permit
D. The maximum daily rainfall amount used for designing detention basins
🟢 A. The maximum amount of a pollutant that a waterbody can receive while still meeting water quality
standards
🔴 RATIONALE: A TMDL is a calculation of the maximum amount of a pollutant that a waterbody can receive
and still meet water quality standards, allocating pollutant loads among point and nonpoint sources .
4. What is the primary purpose of a Stormwater Pollution Prevention Plan (SWPPP)?
A. To enhance recreational water features
B. To identify sources of pollution and outline control measures
C. To increase stormwater runoff
D. To plan for wastewater treatment plant expansions
🟢 B. To identify sources of pollution and outline control measures
🔴 RATIONALE: A SWPPP identifies potential sources of pollution at a site and describes the control measures
,(BMPs) that will be implemented to prevent pollutants from being discharged into receiving waters. It is a key
requirement for NPDES permits .
5. Which stormwater management practice is most effective for reducing peak flow rates from a developed
site?
A. Rain gardens only
B. Detention basins
C. Green roofs
D. Public education on pollution prevention
🟢 B. Detention basins
🔴 RATIONALE: Detention basins are designed to temporarily store stormwater runoff and release it slowly over
time, thereby reducing peak flow rates downstream and mitigating flooding. Rain gardens and green roofs
primarily manage smaller storm events .
6. What is the primary difference between a detention basin and a retention pond?
A. Retention ponds discharge water rapidly
B. Retention ponds hold water permanently; detention ponds hold water temporarily
C. Detention ponds are used for drinking water
D. Retention ponds prevent infiltration
🟢 B. Retention ponds hold water permanently; detention ponds hold water temporarily
🔴 RATIONALE: Retention ponds have a permanent pool of water and provide ongoing water quality treatment,
habitat, and aesthetic benefits, while detention basins are designed to be dry between storm events and only
hold water temporarily to control peak flows .
, 7. Low Impact Development (LID) practices are designed to:
A. Increase stormwater runoff
B. Reduce impervious surfaces and mimic natural hydrology
C. Promote rapid drainage to storm sewers
D. Focus on centralized stormwater treatment
🟢 B. Reduce impervious surfaces and mimic natural hydrology
🔴 RATIONALE: LID emphasizes the use of distributed, small-scale practices that reduce impervious surfaces,
promote infiltration, evapotranspiration, and natural storage to manage runoff at its source, mimicking pre-
development hydrology .
8. Which federal law provides the primary regulatory framework for regulating stormwater discharges in the
United States?
A. Safe Drinking Water Act
B. Clean Water Act
C. Resource Conservation and Recovery Act
D. Comprehensive Environmental Response, Compensation, and Liability Act
🟢 B. Clean Water Act
🔴 RATIONALE: The Clean Water Act, particularly through the NPDES permit program, is the primary federal law
regulating stormwater discharges from municipal separate storm sewer systems (MS4s), construction, and
industrial activities .
9. What does NPDES stand for in stormwater regulation?
ANSWERS) PLUS RATIONALES 2026 Q&A | LATEST EXAM UPDATE 2026/2027
SECTION ONE: QUESTIONS 1-100
1. A stormwater manager is evaluating a proposed residential development that will convert 15 acres of
forest to impervious surfaces. What should be the primary concern regarding the receiving stream?
A. Increased base flow during dry weather
B. Decreased peak flow rates due to faster runoff
C. Increased runoff volume and peak flow rates causing channel erosion
D. Lower pollutant concentrations due to reduced infiltration
🟢 C. Increased runoff volume and peak flow rates causing channel erosion
🔴 RATIONALE: Converting pervious surfaces to impervious cover increases runoff volume and peak flow rates,
which can cause channel erosion, habitat degradation, and downstream flooding. Base flow would typically
decrease due to reduced infiltration, not increase .
2. The Clean Water Act (CWA) of 1972 provides the primary regulatory framework for regulating stormwater
discharges. Which of the following is a critical component of the CWA that regulates stormwater discharges
from construction activities?
A. Safe Drinking Water Act (SDWA)
B. Resource Conservation and Recovery Act (RCRA)
C. National Pollutant Discharge Elimination System (NPDES) permit program
D. Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)
,🟢 C. National Pollutant Discharge Elimination System (NPDES) permit program
🔴 RATIONALE: The NPDES permit program, authorized by Section 402 of the Clean Water Act, regulates the
discharge of pollutants from point sources, including stormwater from construction activities and municipal
separate storm sewer systems .
3. Which of the following is the best definition of a Total Maximum Daily Load (TMDL)?
A. The maximum amount of a pollutant that a waterbody can receive while still meeting water quality standards
B. The minimum daily flow required to maintain navigation in a river
C. The total volume of stormwater that can be discharged from a site without a permit
D. The maximum daily rainfall amount used for designing detention basins
🟢 A. The maximum amount of a pollutant that a waterbody can receive while still meeting water quality
standards
🔴 RATIONALE: A TMDL is a calculation of the maximum amount of a pollutant that a waterbody can receive
and still meet water quality standards, allocating pollutant loads among point and nonpoint sources .
4. What is the primary purpose of a Stormwater Pollution Prevention Plan (SWPPP)?
A. To enhance recreational water features
B. To identify sources of pollution and outline control measures
C. To increase stormwater runoff
D. To plan for wastewater treatment plant expansions
🟢 B. To identify sources of pollution and outline control measures
🔴 RATIONALE: A SWPPP identifies potential sources of pollution at a site and describes the control measures
,(BMPs) that will be implemented to prevent pollutants from being discharged into receiving waters. It is a key
requirement for NPDES permits .
5. Which stormwater management practice is most effective for reducing peak flow rates from a developed
site?
A. Rain gardens only
B. Detention basins
C. Green roofs
D. Public education on pollution prevention
🟢 B. Detention basins
🔴 RATIONALE: Detention basins are designed to temporarily store stormwater runoff and release it slowly over
time, thereby reducing peak flow rates downstream and mitigating flooding. Rain gardens and green roofs
primarily manage smaller storm events .
6. What is the primary difference between a detention basin and a retention pond?
A. Retention ponds discharge water rapidly
B. Retention ponds hold water permanently; detention ponds hold water temporarily
C. Detention ponds are used for drinking water
D. Retention ponds prevent infiltration
🟢 B. Retention ponds hold water permanently; detention ponds hold water temporarily
🔴 RATIONALE: Retention ponds have a permanent pool of water and provide ongoing water quality treatment,
habitat, and aesthetic benefits, while detention basins are designed to be dry between storm events and only
hold water temporarily to control peak flows .
, 7. Low Impact Development (LID) practices are designed to:
A. Increase stormwater runoff
B. Reduce impervious surfaces and mimic natural hydrology
C. Promote rapid drainage to storm sewers
D. Focus on centralized stormwater treatment
🟢 B. Reduce impervious surfaces and mimic natural hydrology
🔴 RATIONALE: LID emphasizes the use of distributed, small-scale practices that reduce impervious surfaces,
promote infiltration, evapotranspiration, and natural storage to manage runoff at its source, mimicking pre-
development hydrology .
8. Which federal law provides the primary regulatory framework for regulating stormwater discharges in the
United States?
A. Safe Drinking Water Act
B. Clean Water Act
C. Resource Conservation and Recovery Act
D. Comprehensive Environmental Response, Compensation, and Liability Act
🟢 B. Clean Water Act
🔴 RATIONALE: The Clean Water Act, particularly through the NPDES permit program, is the primary federal law
regulating stormwater discharges from municipal separate storm sewer systems (MS4s), construction, and
industrial activities .
9. What does NPDES stand for in stormwater regulation?
