19 20 21 22 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 

### Variance 1+ 

### Variance 2+ Triennial review 

### State rulemaking and EPA approval of initial WQS variance Triennial review

Reevaluation at permit reissuance. More stringent HAC not found. No change to WQBEL. Reevaluation at permit reissuance. More stringent HAC identified. Modified WQBEL derived from more stringent HAC. Triennial review Triennial review provides a dditional information 

### State rulemaking and EPA approval of subsequent WQS variance

Permit 5 Permit 1 Permit 2 Permit 3 Permit 4 

# Hypothetical Example of 20

-year WQS Variance Reevaluations Synchronized to NPDES Permit Cycle

Triennial review Triennial review

Reevaluation at permit reissuance using additional information from triennial review. More stringent HAC identified. Modified WQBEL derived from more stringent HAC. WQBEL Year

Permit reissuance. Designated use not attainable, but additional progress possible. Adopt WQS variance. Derive WQBEL from HAC of WQS variance. + Meets all statutory and regulatory requirements. WQBEL

– Water Quality Based Effluent Limit HAC

– Highest Attainable Condition19 20 21 22 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 

### Variance 1+ 

### Variance 2+ Triennial review and reevaluation. More stringent HAC not found. 

### State rulemaking and EPA approval of initial WQS variance

Permit reissuance. No change to WQBEL. Permit reissuance. Modified WQBEL derived from more stringent HAC. Triennial review and reevaluation. More stringent HAC identified 

### State rulemaking and EPA approval of subsequent WQS variance

Permit 5 Permit 1 Permit 2 Permit 3 Permit 4 

# Hypothetical Example of 20

-year WQS Variance Reevaluations Synchronized to Triennial Review Cycle

Triennial review and reevaluation. More stringent HAC not found. Triennial review and reevaluation. More stringent HAC not found.

Permit reissuance. Modified WQBEL derived from more stringent HAC. Triennial review and reevaluation. More stringent HAC not found. Triennial review and reevaluation. More stringent HAC identified

Permit reissuance. Designated use not attainable, but additional progress possible. Adopt WQS variance. Derive WQBEL from HAC of WQS variance. + Meets all statutory and regulatory requirements. WQBEL

– Water Quality Based Effluent Limit HAC

– Highest Attainable Condition WQBEL Year

### WQS Variance 1 

# Hypothetical Example of Coordinating a Discharger

-specific WQS Variance and a Permit Compliance Schedule

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15



### Permit 3 Permit 1

After 15 years, the state could : 1. Establish a new WQBEL derived from the underlying designated use (and a compliance schedule if needed) if the underlying designated use is now attainable ; 2. Consider adopting a subsequent WQS variance with a new HAC and WQBEL (and compliance schedule if needed) if uncertainty remains about the attainability of the underlying designated use ; 3. Consider modifying the designated use if it remains unattainable. Year Underlying designated use WQS HAC and permit WQBEL Current effluent condition



### Permit 2 Permit Compliance Schedule 1 The underlying designated use is not attainable. The highest attainable condition (HAC) can be identified as an effluent condition, but the discharger requires 15 years to attain it. The state is able to justify and adopts a 15

-year WQS variance specifying the HAC, and establishes a water quality

-based effluent limit (WQBEL) equal to the HAC. The state also provides the permittee with a 15

-year compliance schedule that will lead to attainment of the WQBEL “as soon as possible” (in this case 15 years).

1 Meets all statutory and regulatory requirements.