Certified Stormwater Manager (CSM) — Questions and Answers

Question 1: Which executive order requires federal agencies to consider environmental justice in their programs and policies affecting minority and low-income populations?

EO 13148
EO 13690
EO 12898 (Correct answer)
EO 11514

Correct answer: EO 12898

Executive Order 12898 (1994) directs federal agencies to identify and address disproportionately high environmental and health effects on minority and low-income populations.

Question 2: What is required when a stormwater sample result exceeds a benchmark value in the Multi-Sector General Permit (MSGP)?

Immediate facility shutdown
Filing a formal enforcement appeal
Automatic permit revocation
Submission of a corrective action response and SWPPP review (Correct answer)

Correct answer: Submission of a corrective action response and SWPPP review

Exceeding a benchmark triggers a required corrective action response and review of the SWPPP to identify and fix the pollution source.

Question 3: What is the primary purpose of regulatory compliance in professional practice?

To limit the number of practitioners
To protect public safety and ensure minimum standards of care (Correct answer)
To increase operating costs
To create bureaucratic obstacles

Correct answer: To protect public safety and ensure minimum standards of care

Regulatory compliance exists primarily to protect public safety by ensuring all practitioners meet minimum standards of competence and ethical conduct.

Question 4: Green roofs provide stormwater benefits primarily through which mechanism?

Chemically treating runoff through media amendments
Increasing rooftop imperviousness to speed runoff to cisterns
Directing all rooftop runoff to subsurface infiltration galleries
Retaining rainfall in growing media and releasing it through evapotranspiration (Correct answer)

Correct answer: Retaining rainfall in growing media and releasing it through evapotranspiration

Green roofs absorb rainfall into the growing medium and return the majority of it to the atmosphere through evapotranspiration, reducing both runoff volume and peak flow.

Question 5: What does NPDES stand for?

National Permit for Dry Emissions Standards.
National Pipeline Drainage Emergency Service.
National Pollutant Discharge Elimination System (Correct answer)
Neutral Pressure Drainage Efficiency System.

Correct answer: National Pollutant Discharge Elimination System

NPDES stands for National Pollutant Discharge Elimination System. This is a permitting program under the Clean Water Act that controls direct discharges of pollutants into U.S. waters. Facilities that discharge pollutants from a point source into waters of the United States are required to obtain an NPDES permit.

Question 6: Stream order classification in the Strahler system defines a third-order stream as:

A stream formed by the confluence of two second-order streams (Correct answer)
A stream draining a watershed of at least 3 square miles
A stream that has traveled at least 3 miles from its headwaters
Any stream with three or more tributaries

Correct answer: A stream formed by the confluence of two second-order streams

In the Strahler ordering system, two streams of equal order joining creates a stream of the next higher order; therefore, two second-order streams joining creates a third-order stream.

Question 7: A stormwater manager wants to assess whether a restored riparian buffer is reducing nitrogen loading to a stream. What monitoring design would best answer this question?

Single outfall sampling downstream of the buffer during storm events
Upstream-downstream paired monitoring with pre- and post-restoration data collection (Correct answer)
Annual grab sampling at the stream mouth for total nitrogen
Continuous turbidity monitoring at the watershed outlet

Correct answer: Upstream-downstream paired monitoring with pre- and post-restoration data collection

An upstream-downstream paired design with pre- and post-restoration data collection allows the manager to isolate the buffer's effect on nitrogen by accounting for background conditions and temporal variability.

Question 8: Which soil hydrologic group has the highest runoff potential and lowest infiltration rate when thoroughly wet?

Group D (Correct answer)
Group C
Group B
Group A

Correct answer: Group D

Hydrologic Soil Group D consists of soils with very slow infiltration rates (clay soils or soils with a high water table) and produces the highest runoff.

Question 9: Under most NPDES MS4 permit requirements, what is the minimum information that must be maintained in a storm sewer system map for IDDE purposes?

Pipe material only
The location of storm drain inlets, pipes, and outfalls, and the receiving waters to which they drain (Correct answer)
The age and condition rating of each pipe segment
Only outfall locations and receiving water names

Correct answer: The location of storm drain inlets, pipes, and outfalls, and the receiving waters to which they drain

NPDES MS4 permit IDDE requirements specify that the system map must show storm sewer locations, outfalls, and the receiving waters they discharge to, enabling effective field investigations.

Question 10: Under the National Incident Management System (NIMS), the Unified Command structure is used in stormwater emergencies when:

A single agency has full jurisdictional authority
Multiple agencies with different legal authorities are involved (Correct answer)
The incident is limited to one geographic location
Federal resources are not required

Correct answer: Multiple agencies with different legal authorities are involved

Unified Command is activated when multiple agencies with different jurisdictions or legal authorities must coordinate a joint response to the same incident.

Question 11: A watershed with a curve number (CN) of 90 compared to one with CN of 60 will produce:

More infiltration and less surface flow
Less runoff for the same rainfall event
More runoff for the same rainfall event (Correct answer)
The same runoff but with longer time to peak

Correct answer: More runoff for the same rainfall event

Higher curve numbers indicate less permeable, more developed or compacted land, resulting in greater direct runoff for the same precipitation event.

Question 12: What is runoff?

Surface water that flows across the land (Correct answer)
Air humidity levels.
Underground water flow.
Water absorbed by plants.

Correct answer: Surface water that flows across the land

Runoff refers to the portion of precipitation or irrigation water that flows over the land surface, rather than infiltrating into the ground or evaporating. This surface flow can pick up pollutants like sediment, chemicals, and debris, carrying them into storm drains and ultimately into rivers, lakes, and oceans. Managing runoff is a key aspect of stormwater pollution control.

Question 13: What is the recommended minimum dry period (no measurable rainfall) before conducting valid dry-weather outfall screening for illicit discharges?

24 hours
12 hours
7 days
72 hours (Correct answer)

Correct answer: 72 hours

A 72-hour (3-day) dry period is the standard minimum recommended before dry-weather outfall screening, allowing most legitimate stormwater to drain away and making illicit flows more detectable.

Question 14: When sizing a vegetated filter strip for stormwater pretreatment, which parameter is most critical for determining the required width?

Slope of the contributing impervious surface
Species composition of the vegetation
Hydraulic loading rate per unit width (Correct answer)
Soil pH of the filter strip

Correct answer: Hydraulic loading rate per unit width

Hydraulic loading rate (flow per unit width) determines whether sheet flow can be maintained across the filter strip, which is essential for effective pollutant removal.

Question 15: The US EPA's NPDES Phase II permit requires small MS4s to track the effectiveness of BMPs. Which metric best quantifies pollutant load reduction?

Event mean concentration (EMC) alone
Percentage of impervious area within the MS4 boundary
Grab sample turbidity at BMP inlet only
Annual pollutant load (mass/year) before and after BMP installation (Correct answer)

Correct answer: Annual pollutant load (mass/year) before and after BMP installation

Annual pollutant load comparisons (concentration × flow volume × time) before and after BMP installation directly measure mass reduction, which is the relevant metric for permit compliance.

Question 16: What are riparian buffers?

Concrete channels.
Artificial lakes.
Vegetated areas that filter runoff (Correct answer)
Bare soil next to rivers.

Correct answer: Vegetated areas that filter runoff

Riparian buffers are vegetated strips of land located along the banks of rivers, streams, lakes, and other water bodies. These natural or restored areas play a critical role in filtering pollutants from surface runoff, stabilizing stream banks, providing shade to regulate water temperature, and offering habitat for wildlife. They are a key Best Management Practice for protecting water quality.

Question 17: A stormwater manager is updating the emergency contact list in the facility's response plan. Which agency should be listed as the primary federal contact for chemical spills reaching waterways?

U.S. Army Corps of Engineers
Federal Emergency Management Agency (FEMA)
U.S. Geological Survey (USGS)
Environmental Protection Agency (EPA) On-Scene Coordinator (Correct answer)

Correct answer: Environmental Protection Agency (EPA) On-Scene Coordinator

EPA On-Scene Coordinators (OSCs) are the primary federal responders for chemical spills to navigable waters under the National Contingency Plan.

Question 18: What minimum frequency does EPA recommend for reviewing and updating a facility stormwater emergency response plan under normal (non-incident) conditions?

Every 3 years
Every 5 years
Annually (Correct answer)
Every 6 months

Correct answer: Annually

EPA recommends annual review of stormwater emergency response plans to account for personnel changes, new regulatory requirements, and facility modifications.

Question 19: What is the purpose of a TMDL (Total Maximum Daily Load) in the context of stormwater compliance reporting?

To establish the maximum pollutant load a water body can receive while still meeting water quality standards, informing permit limits (Correct answer)
To limit the volume of stormwater that can be detained on-site
To set the maximum equipment load for treatment plants
To define the maximum number of discharge points a facility may operate

Correct answer: To establish the maximum pollutant load a water body can receive while still meeting water quality standards, informing permit limits

A TMDL calculates the maximum pollutant loading a water body can assimilate and is used to set stormwater permit limits that protect water quality.

Question 20: In the SCS/NRCS runoff curve number method, which antecedent moisture condition (AMC) applies to soils that are close to their wilting point?

AMC I (dry) (Correct answer)
AMC II (normal)
AMC III (wet)
AMC IV (saturated)

Correct answer: AMC I (dry)

AMC I represents dry antecedent soil moisture conditions near wilting point, which produces the least runoff for a given rainfall event.

Question 21: Under the Endangered Species Act, stormwater permit applicants may need to consult with which agencies if their discharge could affect listed species?

EPA and Army Corps of Engineers only
State Departments of Agriculture only
FEMA and the Bureau of Land Management
U.S. Fish and Wildlife Service and/or NOAA Fisheries (Correct answer)

Correct answer: U.S. Fish and Wildlife Service and/or NOAA Fisheries

ESA Section 7 consultation is conducted with USFWS (terrestrial and freshwater species) and NOAA Fisheries (marine and anadromous species) for federal actions affecting listed species.

Question 22: Which BMP type removes pollutants primarily through settling and sedimentation rather than biological uptake?

Green roof
Permeable pavement
Wet detention pond (Correct answer)
Vegetated swale

Correct answer: Wet detention pond

Wet detention ponds rely on extended hydraulic retention time to allow suspended solids and associated pollutants to settle out.

Question 23: Which of the following is correctly classified as an illicit discharge to a municipal separate storm sewer system (MS4)?

Uncontaminated groundwater infiltration into storm pipes
Residential car washing wastewater entering a storm drain (Correct answer)
Stormwater runoff from a construction site with an active permit
Irrigation return flows from agricultural operations

Correct answer: Residential car washing wastewater entering a storm drain

Residential car washing wastewater contains soaps, oils, and other pollutants that are prohibited discharges to the storm sewer; it is considered illicit because it is not stormwater.

Question 24: How should a Certified Stormwater Manager professional handle situations beyond their expertise?

Ignore the complexity and apply standard approaches
Refer to a qualified specialist and communicate transparently with the client (Correct answer)
Accept the work to maintain the business relationship
Attempt the work and learn from experience

Correct answer: Refer to a qualified specialist and communicate transparently with the client

Referring to qualified specialists when facing situations beyond personal expertise protects clients and upholds professional integrity.

Question 25: Which BMP reduces erosion on slopes?

Trash bins.
Irrigation pipes.
Storm drains.
Silt fences and erosion blankets (Correct answer)

Correct answer: Silt fences and erosion blankets

Silt fences and erosion blankets are effective BMPs for reducing erosion on slopes. Silt fences are temporary barriers that slow down runoff, allowing sediment to settle out before leaving the site. Erosion blankets, often made of natural fibers, cover exposed soil on slopes to protect it from the impact of rain and wind, stabilizing the soil and promoting vegetation growth.

Question 26: Under the ICS structure used for stormwater emergencies, the Operations Section Chief is responsible for:

Directing all tactical field operations to achieve incident objectives (Correct answer)
Developing the Incident Action Plan and future objectives
Managing media inquiries and public information
Tracking resource costs and budget expenditures

Correct answer: Directing all tactical field operations to achieve incident objectives

The Operations Section Chief manages all tactical response actions in the field, translating the incident objectives from the IAP into actual emergency operations.

Question 27: Under the 'runoff volume reduction' approach to stormwater management, which BMP best addresses the water quality volume by retaining and infiltrating the first flush?

Vegetated filter strip alone
Infiltration basin sized to drawdown within 72 hours (Correct answer)
Detention pond with a large outlet orifice
Bioretention with an underdrain

Correct answer: Infiltration basin sized to drawdown within 72 hours

An infiltration basin that fully drawdowns the water quality volume within 72 hours achieves maximum volume reduction by returning runoff to groundwater.

Question 28: Why is watershed management important?

To eliminate wetlands.
To reduce biodiversity.
To support water quality and ecosystems (Correct answer)
To increase runoff.

Correct answer: To support water quality and ecosystems

Watershed management is important because the health of a water body is directly linked to the health of the land area that drains into it. Effective watershed management involves coordinating land use practices and conservation efforts across the entire basin to protect water quality, maintain healthy ecosystems, prevent flooding, and ensure sustainable water resources for human use and wildlife.

Question 29: In continuous hydrologic simulation modeling, which process must be modeled to properly account for soil moisture between storm events?

Snow accumulation and melt
Interception storage filling
Channel routing and attenuation
Evapotranspiration and soil moisture depletion (Correct answer)

Correct answer: Evapotranspiration and soil moisture depletion

Between storms, ET depletes soil moisture which must be tracked continuously so that the model correctly simulates the antecedent conditions and available storage for each subsequent storm.

Question 30: What is the most important principle in professional Certified Stormwater Manager practice?

Maximizing revenue from each client
Working as quickly as possible
Maintaining competence through continuous learning and adherence to standards (Correct answer)
Following only personal judgment

Correct answer: Maintaining competence through continuous learning and adherence to standards

Maintaining competence through continuous learning and adherence to professional standards ensures quality service delivery and public protection in Certified Stormwater Manager practice.

Question 31: A stormwater manager discovers that sanitary sewage is entering the storm drain system. Under MS4 permit requirements, this represents what type of violation?

An illicit discharge (Correct answer)
A permit transfer violation
A nonpoint source allocation exceedance
A point source exemption

Correct answer: An illicit discharge

Sanitary sewage entering the storm drain system constitutes an illicit discharge — a non-stormwater discharge that is prohibited under MS4 NPDES permit requirements.

Question 32: Which design storm concept is commonly used for sizing water quality treatment BMPs in stormwater management?

The 10-year, 1-hour design storm
A small, frequently occurring storm such as the 90th percentile storm event (Correct answer)
The probable maximum precipitation (PMP) event
The 100-year, 24-hour design storm

Correct answer: A small, frequently occurring storm such as the 90th percentile storm event

Water quality BMPs are typically designed to treat the most frequently occurring runoff events, often the 90th percentile storm, which collectively carry the majority of the annual pollutant load.

Question 33: Which biological indicator is most commonly used to assess stream health impacts from stormwater in the US?

Benthic macroinvertebrate community index (B-IBI) (Correct answer)
Dissolved oxygen depletion rate
E. coli bacteria counts
Total dissolved solids (TDS) concentration

Correct answer: Benthic macroinvertebrate community index (B-IBI)

Benthic macroinvertebrate index of biotic integrity (B-IBI) scores are widely used because these organisms integrate long-term stream conditions and are sensitive to stormwater-related stressors.

Question 34: When calculating an event mean concentration (EMC) for a storm event, what two measured quantities are required?

Total pollutant mass and total runoff volume (Correct answer)
Average turbidity and sampling interval
Antecedent dry period and rainfall intensity
Peak flow and storm duration

Correct answer: Total pollutant mass and total runoff volume

EMC is calculated by dividing the total pollutant mass (load) discharged during a storm event by the total runoff volume for that event.

Question 35: Conservation development designs that preserve sensitive areas such as wetlands, steep slopes, and floodplains achieve which stormwater benefit?

Maintaining natural hydrologic and ecological functions of sensitive areas (Correct answer)
Elimination of on-site detention requirements
Greater impervious coverage of the site
Higher runoff curve numbers

Correct answer: Maintaining natural hydrologic and ecological functions of sensitive areas

Preserving sensitive areas keeps their natural functions—infiltration, storage, ecological filtering—intact, benefiting both hydrology and water quality.

Question 36: A state issues a general permit for a category of stormwater discharges. A facility seeking coverage must typically submit which document to the permitting authority?

Discharge Monitoring Report (DMR)
Letter of Authorization
Individual Permit Application
Notice of Intent (NOI) (Correct answer)

Correct answer: Notice of Intent (NOI)

Facilities seeking coverage under a general permit must file a Notice of Intent (NOI), which notifies the permitting authority that the facility intends to be covered by the general permit.

Question 37: What is hydrology the study of?

Water movement and distribution (Correct answer)
Air pressure.
Wind patterns.
Soil chemistry.

Correct answer: Water movement and distribution

Hydrology is the scientific study of the movement, distribution, and management of water on Earth and other planets. It encompasses the entire water cycle, including precipitation, runoff, infiltration, evaporation, and groundwater flow. Understanding hydrology is fundamental to managing water resources and addressing issues like flooding, drought, and water quality.

Question 38: What does the term 'effluent limitation guideline' (ELG) mean in the context of stormwater documentation?

A recommended BMP for sediment control
A technology-based standard limiting pollutant concentrations in stormwater discharges by industrial category (Correct answer)
A TMDL wasteload allocation for a specific watershed
A state-specific BMR for municipal stormwater

Correct answer: A technology-based standard limiting pollutant concentrations in stormwater discharges by industrial category

ELGs are EPA-established technology-based standards that set pollutant discharge limits for specific categories of industrial facilities.

Question 39: What is the purpose of a Notice of Termination (NOT) under the NPDES Construction General Permit?

To inform the permitting authority that permit coverage is no longer needed upon site stabilization (Correct answer)
To notify regulators that stormwater discharge has begun
To terminate an employee's stormwater responsibilities
To request a permit modification

Correct answer: To inform the permitting authority that permit coverage is no longer needed upon site stabilization

An NOT is submitted when a construction site has achieved final stabilization and permit coverage is no longer required.

Question 40: What is the first critical step in establishing a municipal IDDE program?

Creating and maintaining a complete map of the storm sewer system (Correct answer)
Installing dry-weather flow monitoring equipment at all outfalls
Training field staff in water quality sampling procedures
Issuing fines to businesses with suspected illegal connections

Correct answer: Creating and maintaining a complete map of the storm sewer system

A complete storm sewer system map is the foundation of any IDDE program because field staff must know where pipes go and where outfalls are located before investigating potential illicit connections.

Question 41: How does urban development impact watersheds?

It eliminates flooding.
It improves infiltration.
It increases runoff and pollution (Correct answer)
It boosts vegetation.

Correct answer: It increases runoff and pollution

Urban development significantly impacts watersheds by increasing impervious surfaces like roads, rooftops, and parking lots. These surfaces prevent water from infiltrating into the ground, leading to a greater volume and velocity of stormwater runoff. This increased runoff often carries pollutants such as oil, chemicals, and litter, contributing to water quality degradation and increased flood risk.

Question 42: A grass swale is being designed to convey stormwater while providing water quality treatment. Which parameter is most critical to verify for adequate treatment residence time?

Freeboard above design water surface
Manning's roughness coefficient of concrete lining
Width-to-depth ratio of the channel cross-section
Swale length and longitudinal slope (Correct answer)

Correct answer: Swale length and longitudinal slope

Swale length and longitudinal slope together determine flow velocity and hydraulic residence time, which governs the degree of settling and biological treatment achieved.

Question 43: Under NPDES MS4 permits, which of the following discharges is typically listed as an allowable non-stormwater discharge and is NOT considered illicit?

Washwater from washing out concrete mixers
Discharge from portable toilet cleanouts
Lawn watering and landscape irrigation runoff (Correct answer)
Wastewater from floor drains in auto repair shops

Correct answer: Lawn watering and landscape irrigation runoff

Lawn watering and landscape irrigation runoff are explicitly listed in most NPDES MS4 permits as allowable non-stormwater discharges, provided they do not cause or contribute to water quality violations.

Question 44: A stormwater manager is evaluating a bioretention cell's performance. Which parameter best demonstrates volume reduction effectiveness?

Effluent total suspended solids concentration
Vegetation species diversity in the cell
Difference between influent and effluent total runoff volume (Correct answer)
pH change across the media layer

Correct answer: Difference between influent and effluent total runoff volume

Volume reduction effectiveness is measured by comparing the total volume of stormwater entering the bioretention cell to the total volume discharging from its underdrain.

Question 45: Which practice qualifies as 'pollution prevention' rather than treatment in stormwater management?

Switching to phosphorus-free fertilizers on a golf course (Correct answer)
Installing a vegetated filter strip
Installing a sediment basin
Adding alum to a detention pond

Correct answer: Switching to phosphorus-free fertilizers on a golf course

Using phosphorus-free fertilizers eliminates the pollutant source entirely rather than treating it after it enters runoff, which is true pollution prevention.

Question 46: Which federal regulatory program is the primary driver requiring MS4 operators to develop and implement Illicit Discharge Detection and Elimination (IDDE) programs?

NPDES Phase I and Phase II Stormwater Permit Program (Correct answer)
Safe Drinking Water Act Surface Water Treatment Rule
Clean Water Act Section 401
Resource Conservation and Recovery Act Subtitle D

Correct answer: NPDES Phase I and Phase II Stormwater Permit Program

The NPDES Phase I and Phase II Stormwater Permit Program, under the Clean Water Act, requires regulated MS4 operators to develop IDDE programs as one of six minimum control measures.

Question 47: In stormwater quality monitoring, the 'first flush' phenomenon refers to:

The initial calibration flush performed on ISCO samplers
Flushing sediment accumulated in detention basin forebays
The highest discharge peak during a storm hydrograph
The disproportionately high pollutant concentrations occurring early in a runoff event (Correct answer)

Correct answer: The disproportionately high pollutant concentrations occurring early in a runoff event

First flush describes the tendency for pollutant concentrations to peak early in a storm as accumulated surface pollutants are mobilized before dilution by continued rainfall.

Question 48: Which water quality indicator is most commonly used in field screening to detect the presence of sanitary sewage contamination in stormwater outfall flows?

Turbidity (NTU)
Fecal coliform or E. coli bacteria (Correct answer)
Total dissolved solids (TDS)
Total suspended solids (TSS)

Correct answer: Fecal coliform or E. coli bacteria

Fecal coliform and E. coli are reliable biological indicators of human sewage contamination and are the standard parameters used to confirm sanitary sewer cross-connections in IDDE screening.

Question 49: NPDES MS4 permits typically require municipalities to prohibit illicit discharges through a local regulatory mechanism. What is the most common tool used to establish this legal authority?

A memorandum of understanding with the state environmental agency
A resolution passed by the city council during an open meeting
A local stormwater ordinance or municipal code provision that prohibits non-stormwater discharges to the MS4 (Correct answer)
A conditional use permit issued to each property owner

Correct answer: A local stormwater ordinance or municipal code provision that prohibits non-stormwater discharges to the MS4

A local stormwater ordinance is the standard legal mechanism that grants the municipality authority to prohibit illicit discharges, investigate suspected violations, and enforce corrective actions.

Question 50: What is a vegetative BMP example?

Culverts.
Grassed swales and rain gardens (Correct answer)
Storm grates.
Concrete channels.

Correct answer: Grassed swales and rain gardens

Grassed swales and rain gardens are excellent examples of vegetative BMPs. These systems utilize plants and engineered soil media to filter pollutants, absorb stormwater, and promote infiltration into the ground. They mimic natural processes to manage runoff, enhance water quality, and often provide aesthetic and habitat benefits.

Question 51: A field crew finds ammonia levels elevated at a storm drain outfall during dry weather. Which type of illicit discharge source is MOST consistent with this finding?

Groundwater infiltration into a deteriorated storm pipe
Sanitary sewage or septic system effluent cross-connected to the storm drain (Correct answer)
Cooling water discharge from an industrial HVAC system
Runoff from a fertilized lawn area entering the storm drain

Correct answer: Sanitary sewage or septic system effluent cross-connected to the storm drain

Elevated ammonia in dry-weather outfall flows is a strong indicator of sewage contamination, as ammonia is a breakdown product of urea in human waste and is characteristic of sanitary sewage.

Question 52: Which type of stormwater emergency plan specifically addresses the actions a municipality must take to protect public health when combined sewer overflows (CSOs) occur during heavy rain?

Corrective Action Plan (CAP)
Long-Term Control Plan (LTCP) (Correct answer)
Source Water Protection Plan (SWPP)
Pollution Prevention Plan (PPP)

Correct answer: Long-Term Control Plan (LTCP)

Long-Term Control Plans (LTCPs) are required by EPA for municipalities with combined sewer systems and address emergency management of CSOs to protect public health.

Question 53: What is the term for the portion of precipitation that eventually reaches a stream channel through shallow subsurface flow?

Deep percolation
Overland flow
Interflow (Correct answer)
Baseflow

Correct answer: Interflow

Interflow (also called subsurface stormflow or throughflow) moves laterally through the upper soil horizons and contributes to streamflow during and shortly after storms.

Question 54: Which field parameter, when measured above ambient background levels at a storm drain outfall during dry weather, is a strong indicator of a sanitary sewer cross-connection?

pH between 6.5 and 8.5
Conductivity below 100 µS/cm
Dissolved oxygen below 5 mg/L
Surfactants (detergents) above background levels (Correct answer)

Correct answer: Surfactants (detergents) above background levels

Elevated surfactant levels in dry-weather outfall flow strongly suggest discharge of household or commercial wastewater containing soaps and detergents from an illicit cross-connection.

Question 55: A state wishes to administer its own NPDES program instead of EPA doing so. What must the state obtain?

A federal waiver under Section 101
EPA authorization under Section 402(b) (Correct answer)
An interstate compact approval
A Presidential Executive Order exemption

Correct answer: EPA authorization under Section 402(b)

States can receive authorization to administer the NPDES program under CWA Section 402(b) after demonstrating adequate legal authority and resources.

Question 56: What are Best Management Practices (BMPs)?

Construction materials.
Irrigation systems.
Methods to increase stormwater.
Controls to reduce pollution in stormwater (Correct answer)

Correct answer: Controls to reduce pollution in stormwater

Best Management Practices (BMPs) are techniques or structural controls designed to prevent or reduce the discharge of pollutants into stormwater runoff. Their primary goal is to minimize the environmental impact of development and human activities on water quality. By implementing BMPs, organizations can effectively manage stormwater and comply with environmental regulations.

Question 57: What is a common method of monitoring stormwater systems?

Rocket launches.
Visual inspection (Correct answer)
Infrared scanning.
Seismic analysis.

Correct answer: Visual inspection

Visual inspection is a common and fundamental method for monitoring stormwater systems. It involves physically observing the condition of BMPs, looking for signs of damage, clogging, erosion, or improper installation. This practical approach allows inspectors to quickly assess the functionality and integrity of stormwater controls.

Question 58: Which of the following best describes the role of public education and outreach in an effective IDDE program?

It reduces illicit discharges by informing residents and businesses about what can legally enter storm drains and how to report illegal dumping (Correct answer)
It is only required for Phase I MS4 permits in large urban areas
It is the responsibility of the state environmental agency, not the MS4 operator
It serves primarily to meet permit reporting requirements with minimal operational impact

Correct answer: It reduces illicit discharges by informing residents and businesses about what can legally enter storm drains and how to report illegal dumping

Public education and outreach reduce illicit discharges by raising awareness of proper disposal practices and creating a community reporting network that extends the reach of limited inspection staff.

Question 59: A stage-discharge relationship (rating curve) for a stream gauging station is developed by:

Applying the rational method with local rainfall data
Using Manning's equation with assumed roughness values
Correlating measured water surface elevations with measured streamflow discharges (Correct answer)
Calculating the cross-sectional area times average velocity from Manning's n

Correct answer: Correlating measured water surface elevations with measured streamflow discharges

Rating curves are developed empirically by repeatedly measuring both stage (water surface elevation) and discharge at a station over a range of flow conditions.

Question 60: Which phase of the NPDES permit cycle requires a permittee to submit a renewal application before permit expiration?

Initial permitting phase
Enforcement response phase
Permit reissuance or renewal phase (Correct answer)
Monitoring and reporting phase

Correct answer: Permit reissuance or renewal phase

The permit reissuance phase requires permittees to apply for renewal typically 180 days before the current permit expires.

Question 61: Which certification statement is typically required on a stormwater permit application or report to ensure accountability?

An insurance provider's liability attestation
A notarized property title statement
A neighbor signature confirming awareness
A responsible official's signature certifying accuracy and completeness under penalty of law (Correct answer)

Correct answer: A responsible official's signature certifying accuracy and completeness under penalty of law

NPDES permits require a responsible official to sign a certification statement attesting to the document's truth and accuracy under penalty of law.

Question 62: Which analytical method is approved under 40 CFR Part 136 for measuring total suspended solids (TSS) in stormwater samples?

ASTM D4972 (soil pH measurement)
EPA Method 160.2 (gravimetric filtration and drying) (Correct answer)
Standard Methods 2130 B (nephelometric turbidity)
EPA Method 200.8 (ICP-MS for metals)

Correct answer: EPA Method 160.2 (gravimetric filtration and drying)

EPA Method 160.2 is the approved gravimetric method for TSS, involving filtration through a glass fiber filter and weighing the residue after drying at 103–105°C.

Question 63: When an IDDE inspector discovers a confirmed illicit discharge from a commercial facility, what is the appropriate immediate response?

Issue a warning letter and schedule a reinspection in 90 days
Refer the matter to the EPA Region office and take no local action
Document findings, notify the appropriate regulatory authority, and require the discharger to eliminate the connection within a specified timeframe (Correct answer)
Plug the storm drain outfall to prevent further discharge to the receiving water

Correct answer: Document findings, notify the appropriate regulatory authority, and require the discharger to eliminate the connection within a specified timeframe

Confirmed illicit discharges require documentation, regulatory notification, and an enforcement action requiring the responsible party to eliminate the source within a permit-specified timeframe.

Question 64: Which metric is used to quantify the effectiveness of a stormwater BMP in reducing peak runoff flow rates?

Curve number (CN) reduction
Biochemical oxygen demand (BOD) loading
Event mean concentration (EMC)
Peak flow attenuation ratio (Correct answer)

Correct answer: Peak flow attenuation ratio

Peak flow attenuation ratio compares post-BMP peak discharge to pre-BMP peak discharge, directly measuring a BMP's ability to reduce flooding risk.

Question 65: What is a sediment trap, and how does it differ from a sediment basin?

A sediment trap uses chemical coagulants; a sediment basin relies only on gravity settling
A sediment trap is a small, excavated or bermed impoundment for drainage areas under 5 acres; a sediment basin serves larger areas with more engineered design (Correct answer)
A sediment trap is permanent; a sediment basin is temporary
A sediment trap treats groundwater; a sediment basin treats surface runoff

Correct answer: A sediment trap is a small, excavated or bermed impoundment for drainage areas under 5 acres; a sediment basin serves larger areas with more engineered design

Sediment traps are smaller, simpler impoundments designed for drainage areas up to about 5 acres, while sediment basins are larger engineered structures for bigger contributing areas with outlet control structures.

Question 66: A city's stormwater ordinance prohibits new development from increasing peak runoff rates above pre-development conditions for the 2-year and 10-year storms. This type of standard is best described as:

A hydromodification or peak flow control standard (Correct answer)
A groundwater recharge standard
A water quality volume standard
A first-flush capture standard

Correct answer: A hydromodification or peak flow control standard

Hydromodification or peak flow control standards require post-development peak flows to match pre-development rates for specified design storms to protect channel stability and downstream hydrology.

Question 67: What minimum illumination level (in foot-candles) does OSHA recommend for construction areas where stormwater workers are performing general work tasks?

1 foot-candle
3 foot-candles
5 foot-candles (Correct answer)
10 foot-candles

Correct answer: 5 foot-candles

OSHA 29 CFR 1926.56 requires a minimum of 5 foot-candles of illumination for general construction and work areas.

Question 68: How does permeable pavement reduce stormwater runoff compared to conventional pavement?

By allowing rainfall to infiltrate through the pavement surface into the subbase and underlying soil, reducing runoff volume and peak flow (Correct answer)
By collecting runoff in sub-surface tanks that pump water back onto the road surface
By heating the pavement surface to evaporate rainfall before it can run off
By using rough surface texture to slow runoff velocity without allowing infiltration

Correct answer: By allowing rainfall to infiltrate through the pavement surface into the subbase and underlying soil, reducing runoff volume and peak flow

Permeable pavement has an open pore structure that lets rainfall pass through to a stone storage bed below, where it infiltrates into native soils, significantly reducing surface runoff volume and peak discharge rates.

Question 69: What is the fundamental difference between erosion and sedimentation?

Erosion occurs in streams; sedimentation occurs only on land
Erosion is a natural process; sedimentation is always caused by human activity
Erosion is the detachment and transport of soil particles; sedimentation is the deposition of those transported particles (Correct answer)
Erosion involves chemical weathering; sedimentation involves physical processes only

Correct answer: Erosion is the detachment and transport of soil particles; sedimentation is the deposition of those transported particles

Erosion detaches soil particles from the ground surface through water or wind energy, while sedimentation is the settling and deposition of those transported particles at a new location.

Question 70: What is the primary purpose of conducting dry-weather screening at storm drain outfalls?

To detect non-stormwater flows that may indicate illicit connections or discharges (Correct answer)
To measure peak flow rates for hydraulic modeling
To assess the structural integrity of outfall pipes
To calculate pollutant loading from impervious surfaces

Correct answer: To detect non-stormwater flows that may indicate illicit connections or discharges

Dry-weather screening identifies outfalls with unexplained flows during periods of no recent rainfall, which is a primary indicator of potential illicit connections to sanitary lines or illegal dumping.

Question 71: A designer is selecting a BMP for a site with a high seasonal water table at 18 inches below grade. Which BMP type would be LEAST appropriate?

Infiltration basin (Correct answer)
Extended detention pond
Green roof
Bioretention with a raised underdrain outlet

Correct answer: Infiltration basin

Infiltration basins require adequate vertical separation between the basin bottom and the seasonal high water table (typically ≥2 feet) to function properly and avoid groundwater contamination risks.

Question 72: Which tool is most useful for pre-event emergency planning to identify which areas in a watershed will be inundated first during a major storm event?

Dissolved oxygen monitoring network
Biological assessment surveys
Stormwater GIS mapping with flood inundation layers (Correct answer)
Industrial discharge monitoring reports

Correct answer: Stormwater GIS mapping with flood inundation layers

GIS-based flood inundation mapping overlays watershed topography, drainage infrastructure, and storm modeling to predict which areas flood first during major events.

Question 73: A municipality discovers that a private restaurant has been discharging grease trap waste directly into a storm drain inlet for several months. Under a typical NPDES MS4-mandated IDDE program, what sequence of actions should the municipality take?

Transfer the case to the state environmental agency and take no further action at the local level
Send an educational pamphlet, then wait for the business to self-correct within one year
Install a grease interceptor in the storm drain at municipal expense to mitigate the discharge
Document the discharge, notify the discharger to cease immediately, issue a formal notice of violation, require elimination within a specified timeframe, and conduct a follow-up inspection to confirm compliance (Correct answer)

Correct answer: Document the discharge, notify the discharger to cease immediately, issue a formal notice of violation, require elimination within a specified timeframe, and conduct a follow-up inspection to confirm compliance

IDDE enforcement requires documentation, immediate cessation order, formal notice of violation, a compliance deadline, and follow-up verification — this sequence satisfies both permit obligations and due process requirements.

Question 74: Under the Clean Water Act, which section specifically establishes the National Pollutant Discharge Elimination System (NPDES)?

Section 319
Section 402 (Correct answer)
Section 404
Section 208

Correct answer: Section 402

Section 402 of the Clean Water Act establishes the NPDES permit program that regulates point source discharges into navigable waters.

Question 75: When documenting an IDDE field investigation, which of the following is MOST important to record for potential enforcement action?

Only the address of the suspected source facility
The estimated annual pollutant load from the discharge
Photographic evidence, GPS coordinates, field measurements, time and date of observation, and the name of the inspector (Correct answer)
The weather forecast for the following week

Correct answer: Photographic evidence, GPS coordinates, field measurements, time and date of observation, and the name of the inspector

Thorough documentation including photos, GPS location, field measurements, timestamps, and inspector identification is essential for creating a defensible enforcement record and tracking investigation status.

Question 76: A stormwater inspector finds that sediment has accumulated to 40% of the design storage volume in a dry detention basin. According to standard CSM maintenance thresholds, what action is triggered?

Increase inspection frequency to monthly until sediment reaches 50%
File a non-compliance report with the EPA immediately
Sediment removal is required, as the threshold is typically 25–33% capacity loss (Correct answer)
No action required until 75% capacity is lost

Correct answer: Sediment removal is required, as the threshold is typically 25–33% capacity loss

Most stormwater management standards require sediment removal when accumulation reduces storage capacity by 25–33%, and 40% clearly exceeds that threshold.

Question 77: What is infiltration?

Water forming waves.
Water freezing.
Water soaking into the soil (Correct answer)
Water evaporating into the air.

Correct answer: Water soaking into the soil

Infiltration is the process by which water on the ground surface enters the soil. This is a crucial part of the water cycle, as infiltrated water can replenish groundwater, support plant growth, and reduce surface runoff. The rate of infiltration depends on factors like soil type, vegetation cover, and soil moisture content.

Question 78: Which of the following construction activities would typically require a NPDES Construction General Permit (CGP) at the federal level?

Removing 0.1 acres of pavement
Installing a culvert with no land disturbance
Clearing 1.5 acres for a commercial parking lot (Correct answer)
Grading 0.25 acres for a residential driveway

Correct answer: Clearing 1.5 acres for a commercial parking lot

The CGP applies to construction sites disturbing 1 acre or more (or less than 1 acre if part of a larger common plan), making the 1.5-acre clearing subject to permit requirements.

Question 79: Which chemical tracer is commonly used by inspectors to confirm a specific building's drain is connected to the storm sewer rather than the sanitary sewer?

Sodium chloride (table salt)
Optical brighteners or fluorescent dye (Correct answer)
Potassium permanganate
Sodium hypochlorite (bleach)

Correct answer: Optical brighteners or fluorescent dye

Fluorescent dyes (such as fluorescein or rhodamine) or optical brighteners are introduced into building drains and detected downstream in the storm sewer to confirm an illicit connection.

Question 80: A municipality's emergency stormwater plan should include pre-identified 'critical assets' for protection during major storm events. Which of the following would NOT typically be a critical stormwater asset?

Major detention basin outlet structures
Residential lawn irrigation systems (Correct answer)
Flood control pump stations
Primary trunk line culverts under major roadways

Correct answer: Residential lawn irrigation systems

Residential irrigation systems are private property and do not function as stormwater infrastructure components requiring municipal emergency protection.

Question 81: A constructed stormwater wetland differs from a wet detention pond primarily in that it:

Incorporates shallow marsh zones with emergent vegetation for enhanced treatment (Correct answer)
Relies solely on chemical precipitation to remove pollutants
Uses a lined bottom to prevent groundwater contamination
Has a deeper permanent pool averaging 4–6 feet

Correct answer: Incorporates shallow marsh zones with emergent vegetation for enhanced treatment

Stormwater wetlands incorporate shallow emergent marsh zones (typically 0–18 inches deep) that support biological nutrient cycling and additional pollutant removal beyond simple settling.

Question 82: During an IDDE field investigation, a field technician observes gray, sudsy water flowing from an outfall during dry weather. Which upstream source is MOST likely responsible?

A cross-connected laundry or washing machine drain (Correct answer)
Stormwater ponded in a nearby retention basin
A leaking underground storage tank (UST)
An overflowing sanitary manhole several blocks away

Correct answer: A cross-connected laundry or washing machine drain

Gray, sudsy water during dry weather is a classic sign of laundry or household washing machine wastewater cross-connected to the storm drain, due to the presence of detergents and surfactants.

Question 83: During post-flood emergency operations, crews discover that a bioretention cell has been buried under 2 feet of sediment. The correct immediate action is to:

Assess sediment depth, test for contamination, then develop a restoration plan (Correct answer)
Abandon the facility and redirect drainage to the next downstream conveyance
Plant additional vegetation on top of the deposited sediment
Immediately excavate and remove all sediment to restore function

Correct answer: Assess sediment depth, test for contamination, then develop a restoration plan

Post-flood sediment assessment must include contamination testing before excavation to protect worker safety and prevent secondary contamination during removal.

Question 84: The concept of 'bankfull discharge' is significant in watershed management because it:

Marks the point at which levee overtopping begins
Equals the mean annual flood discharge
Is the flow that does the most geomorphic work and shapes the channel (Correct answer)
Represents the 100-year flood recurrence interval

Correct answer: Is the flow that does the most geomorphic work and shapes the channel

Bankfull discharge, typically corresponding to the 1.5- to 2-year return interval, is responsible for transporting the most sediment and maintaining channel form over time.

Question 85: What is a watershed?

An irrigation technique.
A land area draining into a water body (Correct answer)
A type of water tank.
A water purification device.

Correct answer: A land area draining into a water body

A watershed, also known as a drainage basin, is an area of land where all of the water that falls on it or drains off of it eventually collects and drains into a common outlet, such as a river, lake, or ocean. The boundaries of a watershed are determined by topography, with ridges and hills forming the divides between adjacent watersheds.

Question 86: What is the goal of erosion control in construction sites?

To prevent soil loss and pollution (Correct answer)
To promote runoff.
To create dust clouds.
To increase sediment discharge.

Correct answer: To prevent soil loss and pollution

Erosion control on construction sites is crucial for preventing the detachment and transport of soil particles by wind or water. Uncontrolled erosion leads to significant soil loss from the site and can cause sediment pollution in nearby waterways, harming aquatic ecosystems and reducing water quality. Effective erosion control measures protect both the construction site and the surrounding environment.

Question 87: Under the MSGP, which industrial sector is identified by Sector N?

Landfills, land application sites, and open dumps
Timber products facilities
Scrap recycling and waste recycling facilities (Correct answer)
Chemical and allied products manufacturing

Correct answer: Scrap recycling and waste recycling facilities

Sector N of the MSGP covers scrap recycling and waste recycling facilities, which have specific monitoring and reporting requirements.

Question 88: Which factor most strongly influences the selection between wet pond and dry extended detention basin for stormwater quality treatment in a residential area?

Color preferences of nearby residents
The number of upstream culverts in the system
Local zoning restrictions on fence heights
Availability of year-round baseflow or groundwater to maintain a permanent pool (Correct answer)

Correct answer: Availability of year-round baseflow or groundwater to maintain a permanent pool

Wet ponds require a reliable water source to maintain a permanent pool; without baseflow or groundwater, the pond will dry out and lose its treatment function.

Question 89: Why are stormwater inspections required?

To delay projects.
To avoid cleanup costs.
To report landscaping issues.
To ensure permit compliance (Correct answer)

Correct answer: To ensure permit compliance

Stormwater inspections are regularly required for construction sites and industrial facilities operating under NPDES stormwater permits. These inspections verify that the Best Management Practices (BMPs) outlined in the Stormwater Pollution Prevention Plan (SWPPP) are correctly installed, maintained, and functioning effectively. This ensures ongoing compliance with environmental regulations and prevents pollution.

Question 90: Which water quality parameter is MOST commonly associated with excess stormwater runoff from agricultural fields?

Chlorinated solvents
Petroleum hydrocarbons
Heavy metals
Nitrogen and phosphorus (Correct answer)

Correct answer: Nitrogen and phosphorus

Agricultural runoff is a major source of nitrogen and phosphorus from fertilizers, which cause eutrophication in receiving water bodies.

Question 91: Which soil characteristic most directly limits the feasibility of infiltration BMPs at a given site?

Soil pH and cation exchange capacity
Soil temperature and frost depth
Saturated hydraulic conductivity (Ksat) (Correct answer)
Soil color and organic matter content

Correct answer: Saturated hydraulic conductivity (Ksat)

Saturated hydraulic conductivity determines how quickly water moves through soil; sites with Ksat below 0.5 in/hr are typically poor candidates for infiltration BMPs.

Question 92: During sediment basin cleanout operations, heavy equipment operators are at risk for which condition caused by whole-body vibration over extended shifts?

Heat stroke
Lower back musculoskeletal disorders (Correct answer)
Raynaud's phenomenon
Carpal tunnel syndrome

Correct answer: Lower back musculoskeletal disorders

Prolonged whole-body vibration from heavy equipment is a known cause of lower back musculoskeletal disorders in operators.

Question 93: Which BMP configuration best manages high-frequency, low-volume runoff events (the 'water quality storm') while also providing peak flow attenuation for larger design storms?

An infiltration trench without an overflow bypass
A single large detention pond sized for the 100-year event
A grass swale discharging directly to a receiving stream
A bioretention cell in series with a downstream detention basin (Correct answer)

Correct answer: A bioretention cell in series with a downstream detention basin

Placing a bioretention cell upstream of a detention basin treats small frequent storms for water quality while the basin attenuates peak flows from larger design storms.

Question 94: Tree canopy interception contributes to stormwater management primarily by:

Increasing impervious surface area
Accelerating runoff to streams
Temporarily storing rainfall on leaves and branches before evaporation (Correct answer)
Reducing soil infiltration capacity

Correct answer: Temporarily storing rainfall on leaves and branches before evaporation

Tree canopies intercept rainfall, holding it on leaf surfaces where it evaporates rather than reaching the ground as runoff.

Question 95: Why is BMP design tailored to each site?

To reuse the same design for all sites.
To match site-specific conditions (Correct answer)
To delay construction.
To simplify all plans.

Correct answer: To match site-specific conditions

BMP design is tailored to each site to ensure maximum effectiveness, as every site has unique characteristics. Factors such as soil type, topography, climate, existing vegetation, and land use significantly influence how stormwater behaves and which BMPs will perform best. Customizing designs ensures that the chosen BMPs are appropriate for the specific conditions and achieve optimal pollution control and runoff reduction.

Question 96: During a stormwater emergency, which document serves as the primary operational guide for coordinating multi-agency response?

Stormwater Pollution Prevention Plan (SWPPP)
Incident Command System (ICS) Incident Action Plan (Correct answer)
National Pollutant Discharge Elimination System (NPDES) permit
Standard Operating Procedure manual

Correct answer: Incident Command System (ICS) Incident Action Plan

The Incident Action Plan (IAP) developed within the ICS framework guides multi-agency coordination during stormwater emergencies.

Question 97: Which of the following describes the hydrologic condition 'poor' as used in the SCS curve number tables for pasture or range land?

Lightly grazed with greater than 75% plant cover
Planted with native warm-season grasses
Heavily grazed, less than 50% ground cover (Correct answer)
Recently burned with bare soil exposed

Correct answer: Heavily grazed, less than 50% ground cover

Poor hydrologic condition for pasture/range indicates heavily grazed land with sparse ground cover (less than 50%), resulting in compacted soil and high runoff potential.

Question 98: Which of the following scenarios would most likely trigger a stormwater permit for an existing industrial facility that previously did not need one?

Replacing an aging HVAC system on the roof
Installing a new employee break room inside the existing building
Repainting the exterior of an existing building
Adding outdoor material storage that exposes pollutants to precipitation (Correct answer)

Correct answer: Adding outdoor material storage that exposes pollutants to precipitation

Adding outdoor storage of materials that can be exposed to precipitation can trigger NPDES stormwater permitting requirements for industrial stormwater discharges.

Question 99: What is a green roof and how does it contribute to urban stormwater management?

An elevated green space over a parking structure that collects rainwater for irrigation
A vegetated rooftop system that absorbs and evapotranspirates rainfall, reducing the volume and peak rate of runoff from buildings (Correct answer)
A solar-panel-covered roof that powers the building's stormwater pump system
A roof design that channels all rainfall to a single downspout for monitoring

Correct answer: A vegetated rooftop system that absorbs and evapotranspirates rainfall, reducing the volume and peak rate of runoff from buildings

Green roofs consist of growing media and plants on a rooftop that absorb rainfall, significantly reducing runoff volume and attenuating peak flows from building rooftops in urban areas.

Question 100: Which performance standard is most commonly used in the northeastern United States to size stormwater BMPs for channel protection?

Treat the water quality volume of 1 inch of rainfall
Reduce post-development peak discharge to pre-development rates for the 2-year and 10-year storms (Correct answer)
Match pre-development runoff volume for the 100-year storm
Retain the first 0.5 inches of rainfall on site

Correct answer: Reduce post-development peak discharge to pre-development rates for the 2-year and 10-year storms

The 2-year and 10-year storm peak flow matching standard is widely adopted in the northeast to protect receiving channels from increased erosive flows due to development.

Question 101: What is the function of a sediment basin on a construction site?

To collect and detain runoff so sediment can settle before discharge (Correct answer)
To provide a staging area for excavated material
To divert runoff away from the construction area
To store clean water for dust suppression

Correct answer: To collect and detain runoff so sediment can settle before discharge

A sediment basin temporarily impounds runoff from disturbed areas, allowing suspended sediment to settle before the clarified water is discharged.

Question 102: A stormwater management plan includes a rainwater harvesting cistern. Which design consideration is most important to ensure the cistern provides both water quality and volume reduction benefits?

Sizing the cistern with sufficient drawdown between storms to provide available storage capacity (Correct answer)
Making the cistern as large as possible to store the entire annual runoff volume
Ensuring the cistern overflow discharges directly to a storm drain without treatment
Positioning the cistern above grade to maximize gravity flow to end uses

Correct answer: Sizing the cistern with sufficient drawdown between storms to provide available storage capacity

A cistern only provides volume reduction if it has available capacity when the next storm arrives; adequate drawdown through planned reuse is essential for stormwater management benefits.

Question 103: A construction site disturbing 0.8 acres that is part of a larger common plan of development that will disturb 1.5 acres total — does it require a Construction General Permit?

No, because the individual site is under 1 acre
Yes, because the common plan of development exceeds 1 acre (Correct answer)
Only if the site discharges directly to an impaired water body
Only if the owner has had a prior permit violation

Correct answer: Yes, because the common plan of development exceeds 1 acre

EPA's CGP triggers apply to the entire common plan of development or sale, so if the overall plan disturbs ≥1 acre the permit is required regardless of individual lot size.

Question 104: Which section of the SWPPP describes site-specific Best Management Practices (BMPs) selected to prevent pollutant discharge?

Certification and signature page
Site description and drainage map
Notice of Intent attachment
BMP selection and implementation section (Correct answer)

Correct answer: BMP selection and implementation section

The BMP selection and implementation section identifies and describes the specific controls chosen for the site's pollutant sources.

Question 105: Which document must a regulated industrial facility maintain on-site under the EPA Multi-Sector General Permit (MSGP)?

A Facility Response Plan (FRP)
A Spill Prevention Control and Countermeasure (SPCC) Plan
A Stormwater Pollution Prevention Plan (SWPPP) (Correct answer)
An Environmental Impact Statement (EIS)

Correct answer: A Stormwater Pollution Prevention Plan (SWPPP)

MSGP-covered facilities must develop and implement a SWPPP that identifies pollutant sources and the BMPs used to reduce pollutants in stormwater discharges.

Question 106: Which channel lining material provides the highest Manning's n roughness value and therefore the slowest flow velocities for a given channel geometry and slope?

Concrete
Dense grass (Correct answer)
Smooth asphalt
Riprap

Correct answer: Dense grass

Dense grass has a Manning's n of approximately 0.03–0.10 or higher depending on flow depth, significantly higher than concrete (~0.013) or riprap (~0.033), resulting in slower velocities.

Question 107: What is the purpose of a trash rack or bar screen at a stormwater structure inlet?

To intercept large debris and prevent it from clogging or damaging downstream pipes, culverts, and outlet structures (Correct answer)
To slow stormwater velocity at the inlet to promote sediment settling
To measure total solids concentration in incoming stormwater
To prevent fish and aquatic organisms from entering the storm sewer system

Correct answer: To intercept large debris and prevent it from clogging or damaging downstream pipes, culverts, and outlet structures

Trash racks and bar screens at inlet structures catch large debris such as branches, trash, and leaves before they can clog pipes, damage pumps, or block outlet control structures.

Question 108: What is the primary hydrologic impact of replacing natural land cover with impervious surfaces on water quality?

Decreased total runoff volume but increased peak flows
Increased stormwater runoff volume carrying pollutants accumulated on pavement (Correct answer)
Increased groundwater recharge that dilutes contaminants
Reduced sediment transport due to armored surface conditions

Correct answer: Increased stormwater runoff volume carrying pollutants accumulated on pavement

Impervious surfaces prevent infiltration, increasing both runoff volume and velocity while washing accumulated pollutants such as oils, metals, and nutrients into waterways.

Question 109: What is the role of public education in stormwater compliance?

To encourage illegal dumping.
To promote awareness and pollution prevention (Correct answer)
To eliminate regulations.
To reduce public involvement.

Correct answer: To promote awareness and pollution prevention

Public education is a vital component of effective stormwater management programs. By informing residents, businesses, and developers about the impacts of stormwater pollution and how to prevent it, communities can foster a sense of responsibility and encourage practices that protect water quality. This collective effort helps reduce non-point source pollution and improve overall watershed health.

Question 110: Which maintenance activity is most critical during the first two years after installation of a bioretention facility?

Monthly dredging of accumulated sediment from the surface
Annual replacement of the entire filter media
Weekly inspection of underdrain outflow volume
Irrigation and vegetation management to ensure plant establishment (Correct answer)

Correct answer: Irrigation and vegetation management to ensure plant establishment

Adequate irrigation and weed control during the plant establishment period (typically 1–2 years) is critical to achieve the designed vegetation cover that supports long-term BMP performance.

Question 111: Which of the following outfall observations would be LEAST likely to indicate an illicit discharge during a dry-weather field screening visit?

Oily sheen on the water surface near the outfall
A small trickle of clear, odorless water at an outfall 72 hours after a significant rain event (Correct answer)
Bright orange or reddish staining around the outfall pipe
A persistent flow with a sewage odor and gray coloration

Correct answer: A small trickle of clear, odorless water at an outfall 72 hours after a significant rain event

A small trickle of clear, odorless water 72 hours after significant rainfall is likely base flow or subsurface drainage, a common allowable condition, and is the least indicative of an illicit discharge.

Question 112: A stormwater program wants to detect a 20% reduction in annual total nitrogen load after installing stream buffers. Which data collection design best supports this objective?

Annual dry-weather screening of all MS4 outfalls
One-time watershed-wide land cover mapping using aerial photography
Single outfall grab sample collected once per season
Before-after control-impact (BACI) design with continuous flow and water quality monitoring (Correct answer)

Correct answer: Before-after control-impact (BACI) design with continuous flow and water quality monitoring

A BACI design monitors paired treatment and control watersheds before and after BMP installation, isolating BMP effects from background variability and providing statistically defensible load comparisons.

Question 113: Which outlet structure feature is specifically designed to remove floating pollutants such as trash and oil from a stormwater pond?

Perforated riser pipe
Ogee spillway
Skimmer or reverse slope pipe (Correct answer)
Anti-seep collar

Correct answer: Skimmer or reverse slope pipe

A skimmer or reverse slope pipe draws water from below the surface, preventing floating debris and oils from passing through the outlet during normal operations.

Question 114: What is the recommended approach for tracing an illicit discharge upstream once flow is confirmed at an outfall during dry weather?

Walk the contributing drainage area and systematically check manholes and inlets moving upstream (Correct answer)
Sample the outfall water and wait for laboratory results before any field work
Install automated samplers at the outfall and review data remotely
Issue violation notices to all businesses in the drainage area

Correct answer: Walk the contributing drainage area and systematically check manholes and inlets moving upstream

Systematic upstream manhole and inlet investigation — walking the system from the outfall — is the standard IDDE field methodology to isolate the source of an illicit discharge.

Question 115: When calculating the design infiltration rate for an infiltration BMP, a safety factor is commonly applied to measured field Ksat values. What is the typical safety factor used?

0.25 (one-quarter of measured Ksat)
1.5 (fifty percent greater than measured Ksat)
0.50 (one-half of measured Ksat) (Correct answer)
2.0 (double the measured Ksat)

Correct answer: 0.50 (one-half of measured Ksat)

Designers typically apply a safety factor of 0.5, using half the measured Ksat to account for variability, clogging over time, and construction disturbance of native soils.

Question 116: According to best practice, when should temporary erosion and sediment controls be installed on a construction site?

Before or simultaneously with land disturbance activities (Correct answer)
When a regulatory inspector visits the site
After rough grading is complete
Only during the rainy season

Correct answer: Before or simultaneously with land disturbance activities

Temporary controls must be in place before or at the time land is disturbed to prevent erosion and off-site sediment discharge from the very start of grading.

Question 117: What is the primary purpose of a unit hydrograph in stormwater hydrology?

To estimate average annual runoff from long-term precipitation records
To determine the time of concentration using travel time segments
To relate a unit depth of excess rainfall to a direct runoff hydrograph for a watershed (Correct answer)
To calculate base flow contributions to total streamflow

Correct answer: To relate a unit depth of excess rainfall to a direct runoff hydrograph for a watershed

A unit hydrograph represents the direct runoff response of a watershed to one unit (1 inch or 1 cm) of excess rainfall uniformly distributed over the watershed for a specified duration.

Question 118: An inspector is conducting a dry-weather field screening program to identify illicit discharges. Which observation provides the STRONGEST evidence of a sanitary sewer cross-connection?

Clear water with neutral pH flowing from a storm outfall during dry weather
Turbid, sewage-odored flow with elevated ammonia and surfactant levels at a storm outfall during extended dry weather (Correct answer)
Runoff from landscape irrigation entering a storm inlet
Slight discoloration from iron oxidation in a storm pipe

Correct answer: Turbid, sewage-odored flow with elevated ammonia and surfactant levels at a storm outfall during extended dry weather

Sewage odor combined with elevated ammonia (from urea decomposition) and surfactants (from detergents) in dry-weather storm outfall flow is diagnostic of a sanitary sewer cross-connection or illicit discharge.

Question 119: Why is photo documentation useful in inspections?

They are required only once.
They delay the process.
They reduce inspection quality.
They provide visual compliance evidence (Correct answer)

Correct answer: They provide visual compliance evidence

Photo documentation is highly useful in inspections because it provides objective, visual evidence of compliance or non-compliance. Photos offer a clear, timestamped record of site conditions and BMP status at a specific moment. This visual proof can support inspection findings, track progress of corrective actions, and serve as valuable documentation for regulatory agencies.

Question 120: What is the term for the process of systematically closing down emergency operations and returning to normal stormwater management activities after a major incident?

Incident stabilization
Remediation
Demobilization (Correct answer)
Restoration

Correct answer: Demobilization

Demobilization in ICS refers to the planned, orderly release of resources and personnel and the return to pre-incident operational status.

Question 121: In a low impact development (LID) approach, which strategy best mimics the pre-development hydrograph by reducing both runoff volume and peak discharge?

Increasing pipe conveyance capacity to move runoff quickly off-site
Installing large end-of-pipe detention ponds at the watershed outlet
Distributing multiple small-scale infiltration and retention BMPs throughout the site (Correct answer)
Using impervious surface setbacks from waterways only

Correct answer: Distributing multiple small-scale infiltration and retention BMPs throughout the site

Distributed small-scale LID practices intercept and treat runoff near its source, collectively mimicking pre-development conditions by promoting infiltration, evapotranspiration, and slow release.

Question 122: When inspecting a grass-lined swale for maintenance needs, which condition would MOST warrant immediate corrective action?

Grass height of 8 inches throughout the swale
Slight discoloration of grass from iron in runoff
Isolated bare soil patches less than 1 square foot near the inlet
Rilling and erosion channels cutting through the swale bottom longitudinally (Correct answer)

Correct answer: Rilling and erosion channels cutting through the swale bottom longitudinally

Longitudinal rilling in a grass swale indicates flow velocities are exceeding the protective capacity of the vegetative cover, leading to accelerating erosion that must be corrected.

Question 123: Under the Safe Drinking Water Act, which program specifically protects wellhead areas from stormwater contamination?

Sole Source Aquifer Program
Underground Injection Control Program
Wellhead Protection Program (Correct answer)
Source Water Assessment Program

Correct answer: Wellhead Protection Program

The Wellhead Protection Program (WHPP) under SDWA requires states to delineate protection areas around public water supply wells and manage activities that could contaminate them.

Question 124: Why is staying current with industry developments important for Certified Stormwater Manager professionals?

It is only important for certification renewal
Industry changes rarely affect practice
To provide the best possible service using current knowledge and practices (Correct answer)
Only academic researchers need to stay current

Correct answer: To provide the best possible service using current knowledge and practices

Staying current ensures professionals provide the best possible service by incorporating the latest knowledge, techniques, and regulatory requirements.

Question 125: Which treatment mechanism is primarily responsible for nitrogen removal in a constructed stormwater wetland?

Volatilization of nitrogen gas at the water surface
Gravitational settling of nitrate particles
Adsorption of ammonium onto sand media
Nitrification followed by denitrification in anaerobic zones (Correct answer)

Correct answer: Nitrification followed by denitrification in anaerobic zones

Stormwater wetlands promote nitrification in aerobic surface zones and denitrification in anaerobic substrate zones, converting nitrate to nitrogen gas.

Question 126: Why is it important to use standardized terminology in documentation?

It reduces the amount of writing needed
It is only required in academic settings
It ensures consistent understanding across all readers and reduces ambiguity (Correct answer)
It makes notes look more professional

Correct answer: It ensures consistent understanding across all readers and reduces ambiguity

Standardized terminology ensures all readers interpret documentation consistently, reducing miscommunication and supporting quality care coordination.

Question 127: When a stormwater discharge is regulated under both a municipal MS4 permit and a Construction General Permit, which permit governs?

The MS4 permit always takes precedence
The more stringent of the two permits applies
Both permits apply simultaneously (Correct answer)
The Construction General Permit always takes precedence

Correct answer: Both permits apply simultaneously

Both the MS4 permit and the CGP can apply simultaneously; the operator must comply with all applicable requirements from each permit.

Question 128: Which soil amendment practice most improves the infiltration capacity of compacted urban soils, thereby enhancing stormwater performance?

Compacting topsoil further for uniformity
Applying herbicide to reduce root competition
Adding sand to clay soils only
Incorporating compost to increase organic matter and porosity (Correct answer)

Correct answer: Incorporating compost to increase organic matter and porosity

Adding compost increases soil organic matter, improving soil structure, macropore development, and infiltration capacity in compacted urban soils.

Question 129: A city's stormwater permit includes a numeric effluent limitation for total suspended solids. The city cannot meet the limit due to budget constraints. What is the appropriate course of action?

Seek a permit modification or variance through the permitting authority (Correct answer)
Cease all discharges until funding is secured
Transfer the permit to the county
Continue operating and document the budget issue in the annual report

Correct answer: Seek a permit modification or variance through the permitting authority

When compliance with a permit limit is infeasible, the permittee must engage the permitting authority to seek a formal permit modification or variance rather than simply continuing non-compliant discharges.

Question 130: A stormwater monitoring program requires quarterly sampling of a detention pond's discharge. Samples must be collected as 'flow-weighted composite' samples. What does this method entail?

Collecting aliquots proportional to flow rate so high-flow periods are represented proportionally (Correct answer)
Averaging results from three grab samples taken at the beginning, middle, and end of storm
Collecting equal-volume aliquots at fixed time intervals regardless of flow
Collecting a single grab sample at peak flow only

Correct answer: Collecting aliquots proportional to flow rate so high-flow periods are represented proportionally

Flow-weighted composite sampling collects aliquot volumes proportional to instantaneous flow rate, ensuring the composite sample accurately represents the pollutant load discharged.

Question 131: In watershed delineation, a 'pour point' refers to:

The highest elevation point on the watershed boundary
The location of maximum soil infiltration rate
A point where two stream tributaries merge
The outlet or lowest point through which all watershed runoff exits (Correct answer)

Correct answer: The outlet or lowest point through which all watershed runoff exits

The pour point (or watershed outlet) is the single point at the lowest elevation through which all surface water within the delineated watershed drains.

Question 132: When designing a vegetated filter strip, the recommended maximum slope to ensure uniform sheet flow and adequate treatment is:

2%
15%
10%
5% (Correct answer)

Correct answer: 5%

Filter strips are typically designed with slopes of 2–5%, with 5% being a common upper limit to maintain sheet flow and prevent channelization that bypasses treatment.

Question 133: What is the primary function of secondary containment systems at industrial facilities in a stormwater emergency context?

To prevent spilled materials from reaching stormwater conveyances (Correct answer)
To provide emergency water supply for fire suppression
To filter pollutants before discharge to municipal systems
To store treated stormwater for reuse

Correct answer: To prevent spilled materials from reaching stormwater conveyances

Secondary containment systems (berms, dikes, vaults) are designed to capture spills at the source and prevent them from entering stormwater drainage systems.

Question 134: Which bioremediation technique uses plants to extract heavy metals from contaminated stormwater sediments?

Rhizofiltration
Constructed wetland polishing
Phytoremediation (Correct answer)
Biofiltration

Correct answer: Phytoremediation

Phytoremediation uses hyperaccumulator plants to take up and concentrate heavy metals from contaminated soil and water.

Question 135: The dimensionless unit hydrograph developed by the NRCS is characterized by:

A recession limb that is longer than the rising limb (Correct answer)
37% of the total volume occurring before the peak
A time to peak equal to the storm duration
A symmetric shape with equal rising and falling limbs

Correct answer: A recession limb that is longer than the rising limb

The NRCS dimensionless unit hydrograph has a skewed shape where the recession limb extends approximately 1.67 times longer than the rising limb, reflecting slower groundwater drainage.

Question 136: A developer proposes to fill a wetland that provides 50 acre-feet of floodwater storage. Under the watershed management perspective, this action would most likely:

Increase downstream flood peaks by eliminating natural detention storage (Correct answer)
Decrease sediment transport capacity in downstream reaches
Reduce downstream peak flows by improving channel conveyance
Have no effect on downstream flows if compensatory storage is provided upstream

Correct answer: Increase downstream flood peaks by eliminating natural detention storage

Wetlands attenuate flood peaks by temporarily storing floodwater; eliminating this storage increases and accelerates downstream runoff, raising peak flows.

Question 137: Which of the following best describes a 'sanitary sewer cross-connection' in the context of an MS4 system?

An overflow structure on a combined sewer that diverts excess flow during storms
A physical connection between a building's sanitary drain and the storm sewer that allows sewage to enter the storm system (Correct answer)
A sewer manhole that is shared between the storm and sanitary systems for maintenance access
A pipe that carries both stormwater and treated wastewater to the same outfall

Correct answer: A physical connection between a building's sanitary drain and the storm sewer that allows sewage to enter the storm system

A sanitary sewer cross-connection occurs when a building's plumbing — either intentionally or by error — routes sewage into the storm sewer instead of the sanitary sewer, causing illicit discharge.

Question 138: What is the primary purpose of maintaining accurate professional documentation?

To create a legal record of services and support continuity of care (Correct answer)
To fill storage space with records
To satisfy billing department requirements only
To create work for administrative staff

Correct answer: To create a legal record of services and support continuity of care

Accurate documentation creates a legal record, supports continuity of care, facilitates communication among providers, and protects both practitioner and client.

Question 139: What is low impact development (LID)?

Natural techniques for local stormwater control (Correct answer)
An underground reservoir.
A large dam project.
A high-cost stormwater method.

Correct answer: Natural techniques for local stormwater control

Low Impact Development (LID) is an approach to stormwater management that mimics natural hydrologic processes to manage stormwater on-site. It employs a variety of natural techniques, often referred to as green infrastructure, such as rain gardens, permeable pavements, and vegetated swales. The goal of LID is to manage stormwater close to its source, reducing runoff volume and improving water quality through infiltration, filtration, and evapotranspiration.

Question 140: Which hydrologic process describes the movement of water from the soil surface into the soil profile?

Infiltration (Correct answer)
Exfiltration
Interflow
Percolation

Correct answer: Infiltration

Infiltration is the process by which water on the ground surface enters the soil, while percolation refers to downward movement through the saturated zone.

Question 141: Why monitor watershed health?

To reduce reporting.
To increase impervious surfaces.
To detect pollution and other issues (Correct answer)
To avoid maintenance.

Correct answer: To detect pollution and other issues

Monitoring watershed health involves regularly collecting data on water quality, aquatic life, habitat conditions, and other environmental indicators. This monitoring is essential for detecting sources of pollution, identifying ecological degradation, assessing the effectiveness of management strategies, and ensuring the long-term sustainability of water resources and ecosystems within the watershed.

Question 142: Why are Best Management Practices (BMPs) used in stormwater management?

To reduce taxes.
To control and reduce stormwater pollution (Correct answer)
To monitor wildlife only.
To increase pollution.

Correct answer: To control and reduce stormwater pollution

Best Management Practices (BMPs) are techniques, measures, or structural controls used to manage the quantity and improve the quality of stormwater runoff. They are implemented to prevent or reduce the discharge of pollutants into waterways. Examples include sediment basins, silt fences, vegetated swales, and permeable pavements.

Question 143: An industrial facility operating under a Multi-Sector General Permit (MSGP) must conduct stormwater sampling. What are these samples primarily used to assess?

The facility's compliance with air quality standards
Annual groundwater recharge rates
The effectiveness of wastewater treatment systems
Whether the facility's stormwater discharges exceed benchmark values (Correct answer)

Correct answer: Whether the facility's stormwater discharges exceed benchmark values

Under the MSGP, benchmark monitoring results are compared to benchmark values to help facilities assess whether their BMPs are adequately controlling pollutants in stormwater discharges.

Question 144: A stormwater manager receives a report of an unknown sheen on the surface of a retention pond. Under the Clean Water Act, sheens from petroleum products:

Must be reported to the National Response Center if from a vessel or facility (Correct answer)
Are exempt from reporting if naturally occurring
Only require reporting if they affect drinking water sources
Are permitted if the volume is below 1 gallon

Correct answer: Must be reported to the National Response Center if from a vessel or facility

The Clean Water Act requires reporting petroleum sheens to the National Response Center (NRC) at 1-800-424-8802 when caused by discharges from vessels or facilities.

Question 145: A watershed manager notices that baseflow in a stream has declined significantly over 20 years despite similar rainfall patterns. The most likely cause is:

Reduction in groundwater recharge due to expanded impervious cover (Correct answer)
Increased evapotranspiration from invasive riparian vegetation
Installation of upstream dams reducing downstream flow
Increased stream channel erosion reducing bed elevation

Correct answer: Reduction in groundwater recharge due to expanded impervious cover

Impervious surfaces prevent infiltration and groundwater recharge; over time, declining aquifer levels reduce the groundwater contribution that sustains baseflow between storms.

Question 146: Which material is most commonly used as a stabilized construction entrance to reduce tracking of mud onto public roads?

Wood chip mulch
Compacted native soil
Concrete poured over geotextile
Crushed stone or gravel pad (Correct answer)

Correct answer: Crushed stone or gravel pad

A stabilized construction entrance uses crushed stone or aggregate over geotextile fabric to knock mud off vehicle tires as they leave the site, preventing sediment tracking onto roads.

Question 147: Which term describes the process of reviewing monitoring data to determine whether a facility is meeting its permit effluent limits?

Load reduction analysis
Compliance determination (Correct answer)
Baseline characterization
Watershed delineation

Correct answer: Compliance determination

Compliance determination involves comparing monitoring data against permit limits to assess whether the facility is in compliance.

Question 148: Which type of NPDES permit is issued to a single, specific discharger rather than a broad category of dischargers?

Categorical permit
Sector-specific permit
General permit
Individual permit (Correct answer)

Correct answer: Individual permit

An individual permit is tailored to a specific facility's unique discharge characteristics and is not a general or sector-based permit.

Question 149: Which of the following entities is NOT typically subject to IDDE inspections by an MS4 operator?

Restaurants and food service establishments
Automotive repair shops and car washes
Industrial facilities discharging to the municipal storm sewer
Federally owned facilities with their own stormwater permits (Correct answer)

Correct answer: Federally owned facilities with their own stormwater permits

Federally owned facilities with their own separate NPDES stormwater permits are regulated independently and are generally not subject to MS4 IDDE inspections by the local municipality.

Question 150: Which sampling strategy collects individual discrete samples at fixed time intervals regardless of flow conditions?

Time-composite sampling (Correct answer)
Event mean concentration sampling
Grab sampling at peak flow
Flow-proportional composite sampling

Correct answer: Time-composite sampling

Time-composite sampling collects aliquots at set time intervals (e.g., every 15 minutes), independent of the actual flow rate during the storm event.

Question 151: Evapotranspiration (ET) is typically highest in watersheds that have:

Dense vegetation, warm temperatures, and ample soil moisture (Correct answer)
Shallow water tables and clay-rich soils
Steep slopes with rapid runoff generation
High impervious cover and minimal vegetation

Correct answer: Dense vegetation, warm temperatures, and ample soil moisture

ET requires energy (solar radiation and heat), available water, and leaf area to transpire moisture; dense vegetated watersheds with warm climates and moist soils maximize ET losses.

Question 152: In NRCS TR-55 methodology, which of the following contributes to the 'sheet flow' portion of time of concentration calculation?

Flow in defined natural or constructed channels
Flow in storm sewers and culverts
Overland flow on unpaved or paved surfaces for distances up to 300 feet (Correct answer)
Subsurface flow through soil macropores

Correct answer: Overland flow on unpaved or paved surfaces for distances up to 300 feet

Sheet flow is the initial overland flow phase, occurring over plane surfaces (grass, pavement, bare soil) for distances up to 300 feet before concentrating into shallow concentrated flow or channels.

Certified Stormwater Manager (CSM)

The CSM certification, administered by APWA, validates professional competency in municipal stormwater program management including regulatory compliance, hydrology, erosion and sediment control, illicit discharge elimination, BMP design, and program administration.

150

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210 min

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70%

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