CPESC Water Quality Standards 5 — Questions and Answers
Question 1: What is the purpose of a Section 401 Water Quality Certification under the Clean Water Act?
- To authorize NPDES stormwater permits for large construction sites
- To ensure that federally permitted activities comply with state water quality standards (Correct answer)
- To establish TMDLs for impaired water bodies
- To grant variances from numeric effluent limitations
Correct answer: To ensure that federally permitted activities comply with state water quality standards
Section 401 certification is issued by states to certify that a federally permitted activity (like a Section 404 wetland fill) will comply with state water quality standards.
Question 2: In a TMDL calculation, what does the 'margin of safety' (MOS) account for?
- Future population growth and increased discharge volumes
- Uncertainty in data, modeling, and the relationship between pollutant loads and water quality (Correct answer)
- The buffer zone around critical habitat areas
- Administrative time needed to implement corrective actions
Correct answer: Uncertainty in data, modeling, and the relationship between pollutant loads and water quality
The margin of safety accounts for uncertainties in data quality, modeling assumptions, and the relationship between pollutant loads and resulting water quality conditions.
Question 3: Which stormwater management approach is most effective at reducing total phosphorus loads from construction sites before discharge to sensitive water bodies?
- Street sweeping of adjacent roadways
- Installation of a sediment basin with a chemical treatment system (Correct answer)
- Increasing the velocity of discharge to dilute concentrations
- Planting fast-growing annual grasses
Correct answer: Installation of a sediment basin with a chemical treatment system
Sediment basins combined with chemical treatment (such as polyacrylamide or alum) effectively flocculate and settle fine particles and phosphorus bound to sediment.
Question 4: Under EPA regulations, which of the following water bodies receives Tier 2 protection under antidegradation policy?
- Waters already failing to meet water quality standards
- Waters that exceed water quality standards — better than required (Correct answer)
- Waters designated as Outstanding National Resource Waters
- Waters with approved TMDLs in place
Correct answer: Waters that exceed water quality standards — better than required
Tier 2 antidegradation protection applies to waters where quality exceeds levels necessary to support designated uses — these must be maintained and protected from degradation.
Question 5: A construction contractor observes a spill of hydraulic fluid reaching a storm drain that discharges to a local creek. Under CWA requirements, what is the immediate obligation?
- Document the spill in the SWPPP and notify the permitting authority within 30 days
- Implement containment and cleanup immediately, and notify the appropriate regulatory agency as required by permit conditions (Correct answer)
- Wait for the next inspection to report the incident to the SWPPP preparer
- Apply for a permit modification before taking any remedial action
Correct answer: Implement containment and cleanup immediately, and notify the appropriate regulatory agency as required by permit conditions
Spills reaching surface waters require immediate containment and cleanup actions, followed by regulatory notification within the timeframe specified in the applicable permit.
Question 6: Which stormwater quality parameter is typically used to assess overall effectiveness of sediment control BMPs at a construction site?
- pH
- Total Suspended Solids (TSS) (Correct answer)
- Dissolved oxygen
- Chloride concentration
Correct answer: Total Suspended Solids (TSS)
Total Suspended Solids (TSS) is the primary indicator of sediment control BMP performance, directly measuring the particle load being discharged from a construction site.
Question 7: What is the significance of the 'load allocation' (LA) component within a TMDL for construction stormwater management?
- It sets permit limits for NPDES-regulated construction sites
- It represents the pollutant load assigned to nonpoint sources and background sources (Correct answer)
- It calculates the total loading capacity of the receiving water body
- It establishes the compliance schedule for point source dischargers
Correct answer: It represents the pollutant load assigned to nonpoint sources and background sources
The load allocation (LA) represents the portion of a TMDL's allowable pollutant load assigned to nonpoint sources (like unregulated stormwater runoff) and natural background levels.
CPESC Water Quality Standards 5
What is the purpose of a Section 401 Water Quality Certification under the Clean Water Act?