CPESC Water Quality Standards 3 — Questions and Answers
Question 1: Under EPA's Construction General Permit (CGP), what is the typical turbidity benchmark value that triggers additional BMP evaluation?
- 25 NTU
- 50 NTU
- 100 NTU (Correct answer)
- 280 NTU
Correct answer: 100 NTU
EPA's CGP establishes a turbidity benchmark of 280 NTU for most receiving waters, but many state permits set lower benchmarks such as 50 or 100 NTU.
Question 2: Which Clean Water Act section requires states to develop water quality standards and submit them to EPA for approval?
- Section 301
- Section 303 (Correct answer)
- Section 319
- Section 401
Correct answer: Section 303
Section 303 of the Clean Water Act requires states to establish water quality standards and submit them to EPA for review and approval.
Question 3: What distinguishes a 'narrative criterion' from a 'numeric criterion' in water quality standards?
- Narrative criteria apply only to groundwater; numeric to surface water
- Narrative criteria describe qualitative conditions; numeric criteria specify measurable concentrations or values (Correct answer)
- Narrative criteria are federally set; numeric criteria are state-specific
- Narrative criteria apply to point sources only
Correct answer: Narrative criteria describe qualitative conditions; numeric criteria specify measurable concentrations or values
Narrative criteria describe qualitative conditions (e.g., 'no visible sheen') while numeric criteria specify measurable limits for specific pollutants.
Question 4: A construction project near an Outstanding National Resource Water (ONRW) is proposed. Which statement is most accurate regarding water quality protection?
- Standard NPDES permit conditions apply without modification
- No new or increased discharges that cause degradation are allowed (Correct answer)
- Antidegradation review is waived for temporary construction activities
- Only TSS limits are more restrictive than standard waters
Correct answer: No new or increased discharges that cause degradation are allowed
ONRWs receive the highest level of protection under antidegradation policy — no new or increased discharges that would degrade water quality are permitted.
Question 5: Which pollutant from construction sites is most directly regulated by the TMDL process when a water body is listed as impaired?
- Carbon dioxide
- Sediment/turbidity (Correct answer)
- Atmospheric nitrogen deposition
- Groundwater contaminants
Correct answer: Sediment/turbidity
Sediment and turbidity are among the most common reasons water bodies appear on 303(d) impaired waters lists, and TMDLs are developed to address these impairments.
Question 6: What is a 'waste load allocation' (WLA) within a TMDL framework?
- The total pollutant load a watershed can receive
- The portion of a TMDL assigned to regulated point sources (Correct answer)
- The pollutant reduction required from nonpoint sources
- The safety margin built into TMDL calculations
Correct answer: The portion of a TMDL assigned to regulated point sources
A waste load allocation (WLA) is the portion of a TMDL's allowable pollutant load assigned specifically to point sources regulated under NPDES permits.
Question 7: Fecal coliform and E. coli standards in water quality criteria primarily protect which designated use?
- Industrial water supply
- Agricultural irrigation
- Primary contact recreation (swimming) (Correct answer)
- Navigation and boat traffic
Correct answer: Primary contact recreation (swimming)
Fecal coliform and E. coli criteria are established to protect primary contact recreation uses, particularly swimming, where human exposure to pathogens is highest.
CPESC Water Quality Standards 3
Under EPA's Construction General Permit (CGP), what is the typical turbidity benchmark value that triggers additional BMP evaluation?