Mixed Deck — All CSM Topics Flashcards

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

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.

Which document serves as the primary on-site compliance record for construction sites under the Construction General Permit?

Answer: Stormwater Pollution Prevention Plan (SWPPP)

The SWPPP is the foundational on-site document that details BMPs and serves as the primary compliance record for construction sites.

What does 'MEP' stand for in the context of MS4 stormwater permit compliance?

Answer: Maximum Extent Practicable

MEP (Maximum Extent Practicable) is the performance standard that MS4 operators must achieve in reducing pollutants in stormwater discharges.

A CSM inspector is evaluating a permeable pavement parking lot that shows ponding water 48 hours after a rain event. What is the FIRST diagnostic step?

Answer: Perform an infiltration test (e.g., ASTM C1701) to quantify the current infiltration rate versus design rate

An infiltration test quantifies how severely clogging has reduced permeability, which determines whether maintenance (vacuum sweeping, pressure washing) can restore function or replacement is needed.

What is residual risk?

Answer: The risk remaining after mitigation measures have been applied

Residual risk is what remains after mitigation measures are applied, and it must be accepted, further reduced, or transferred based on organizational risk tolerance.

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

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.

Which GIS-based method is commonly used to delineate watershed boundaries for stormwater assessment?

Answer: Digital elevation model (DEM) flow direction analysis

Watershed delineation using GIS relies on digital elevation model (DEM) analysis to determine flow direction and accumulation, identifying the drainage area contributing to a point of interest.

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?

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.

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

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.

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?

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.

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

Answer: Permit reissuance or renewal phase

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

What is considered an illicit discharge?

Answer: Unauthorized pollutants into storm drains

An illicit discharge refers to any discharge to an MS4 that is not composed entirely of stormwater, except for discharges allowed under an NPDES permit or specifically exempted by regulation. Common illicit discharges include sanitary wastewater, car wash waste, oil, chemicals, and improper disposal of trash, all of which can severely pollute receiving waters.

A developer proposes a cluster development design that preserves 40% of a site as open space. How does this primarily benefit stormwater management?

Answer: It maintains natural infiltration and reduces runoff-generating surfaces

Clustering development concentrates impervious surfaces, preserving natural areas that maintain pre-development infiltration capacity and reduce runoff volume.

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

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.

When reporting stormwater monitoring results to a regulatory agency, data flagged with a 'J' qualifier means:

Answer: The result is estimated because it falls below the reporting limit but above the detection limit

A 'J' qualifier (estimated value) indicates a concentration was detected but falls in the range between the method detection limit and the practical quantitation limit, making it a semi-quantitative estimate.

In arid and semi-arid regions of the US, stormwater harvesting practices are particularly valuable because they:

Answer: Capture infrequent but intense precipitation events for beneficial reuse

In arid regions, capturing high-intensity storm runoff for irrigation and non-potable uses conserves scarce water resources while managing stormwater volume.

Which provision of the Clean Water Act authorizes citizens or organizations to sue a permit violator directly when the government has not taken timely enforcement action?

Answer: Section 505 Citizen Suits

CWA Section 505 authorizes citizen suits against any person alleged to be in violation of an effluent standard or permit condition, serving as a powerful enforcement backstop.

A site designer wants to use a dry extended detention basin. Which pollutant removal mechanism is least effective in this BMP compared to a wet pond?

Answer: Biological nutrient uptake by aquatic plants

Dry basins drain between storms and lack a permanent pool, so aquatic vegetation cannot establish and biological nutrient uptake is minimal.

What does 'no exposure' certification allow certain industrial facilities to avoid?

Answer: Obtaining NPDES stormwater permit coverage

Facilities that can certify all industrial materials and activities are protected from stormwater contact (no exposure) may qualify for an exemption from NPDES industrial stormwater permit coverage.

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

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.