CSM Inspection Monitoring & Maintenance Procedures 3 — Questions and Answers
Question 1: 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?
- Replace the entire pavement surface immediately
- Perform an infiltration test (e.g., ASTM C1701) to quantify the current infiltration rate versus design rate (Correct answer)
- Add topsoil to the surface to improve drainage
- Install a French drain around the perimeter
Correct 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.
Question 2: Which of the following best describes the 'dead storage' zone in a stormwater wet pond, and why is monitoring its volume important?
- The zone above the permanent pool used for temporary flood storage; monitoring prevents overtopping
- The permanent pool volume below the outlet; monitoring tracks sediment accumulation that reduces water quality treatment capacity (Correct answer)
- The emergency spillway area; monitoring ensures it is free of vegetation
- The dry buffer zone around the pond perimeter; monitoring prevents encroachment
Correct answer: The permanent pool volume below the outlet; monitoring tracks sediment accumulation that reduces water quality treatment capacity
Dead storage is the permanent pool below the outlet structure that provides water quality treatment; as sediment fills this zone, pollutant removal efficiency declines and cleanout is needed.
Question 3: An inspector documents that a stormwater inlet grate has a 3-inch vertical deflection from vehicle traffic. What is the primary concern with this condition?
- Aesthetic appearance of the roadway
- Structural failure risk and potential for grate to become a safety hazard or allow larger debris to enter the system (Correct answer)
- Increased stormwater capture efficiency due to larger opening
- Violation of ADA accessibility requirements only
Correct answer: Structural failure risk and potential for grate to become a safety hazard or allow larger debris to enter the system
A deformed inlet grate is a structural deficiency that can fail completely under traffic load, creating a safety hazard and potentially allowing large debris to block downstream pipes.
Question 4: When establishing a routine maintenance schedule for an underground stormwater detention vault, which factor MOST influences the inspection frequency?
- The color of the vault's interior coating
- The contributing drainage area's land use and associated sediment/pollutant loading (Correct answer)
- The vault manufacturer's country of origin
- The distance from the vault to the nearest surface water body
Correct answer: The contributing drainage area's land use and associated sediment/pollutant loading
High-sediment-loading land uses like construction sites or unpaved areas require more frequent inspection and cleanout than low-loading residential catchments.
Question 5: A stormwater inspector observes an oily sheen on the permanent pool of a wet detention pond serving a commercial strip mall. Under which regulatory program must this observation MOST likely be reported?
- RCRA (Resource Conservation and Recovery Act) only
- NPDES stormwater permit and potentially as a spill under Clean Water Act Section 311 if petroleum is confirmed (Correct answer)
- Only to the local building department
- No reporting required unless the sheen persists more than 30 days
Correct answer: NPDES stormwater permit and potentially as a spill under Clean Water Act Section 311 if petroleum is confirmed
An oil sheen on a stormwater BMP may indicate an illicit discharge or spill, triggering NPDES illicit discharge detection and elimination (IDDE) investigation and potential CWA Section 311 spill reporting.
Question 6: What is the recommended minimum frequency for inspecting high-hazard stormwater ponds with earthen embankments under most state dam safety programs?
- Once every 10 years by an owner's representative
- Annually by a licensed professional engineer with dam safety experience (Correct answer)
- Only after storms exceeding the 100-year design storm
- Every 5 years by a certified inspector
Correct answer: Annually by a licensed professional engineer with dam safety experience
High-hazard dams and pond embankments typically require annual inspections by a licensed professional engineer under state dam safety regulations due to the life-safety risk of failure.
Question 7: During vegetated filter strip maintenance, an inspector finds that the contributing impervious area now drains as concentrated flow through a channel rather than as sheet flow across the strip. What maintenance action is required?
- Convert the filter strip to a grass swale to accommodate concentrated flow
- Install a level spreader or flow spreader device at the inlet to re-establish sheet flow conditions (Correct answer)
- Do nothing, as filter strips function equally well with concentrated or sheet flow
- Remove the filter strip and install a sediment trap
Correct answer: Install a level spreader or flow spreader device at the inlet to re-establish sheet flow conditions
Vegetated filter strips depend on sheet flow for effective sediment and pollutant removal; concentrated flow bypasses most of the treatment area, so a level spreader must be installed to restore design function.
CSM Inspection Monitoring & Maintenance Procedures 3
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?