Code of Colorado Regulations
1000 - Department of Public Health and Environment
1002 - Water Quality Control Commission (1002 Series)
5 CCR 1002-34 - REGULATION NO. 34 - CLASSIFICATIONS AND NUMERIC STANDARDS FOR SAN JUAN AND DOLORES RIVER BASINS
Section 5 CCR 1002-34.53 - STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE; DECEMBER 14, 2020 RULEMAKING; FINAL ACTION FEBRUARY 8, 2021 EFFECTIVE DATE JUNE 30, 2021

A. La Plata Segment 7a

The commission adopted a discharger specific variance (DSV) for La Plata Segment 7a (COSJLP07a) for ammonia that represents the highest degree of protection of the classified use that is economically feasible for Vista Verde Village Mobile Home Park (Vista Verde). The ammonia acute and chronic alternative effluent limits are, 24 mg/L from November through April and 14 mg/L from May through October. The seasonal change in limits is intended to address changes in treatment performance due to temperature. Since aerated lagoons have long detention times (greater than 30 days) and do not provide the opportunity to control for daily variation, the AELs shall apply to both the acute and chronic WQBELs. The DSV requires that Vista Verde's ammonia effluent concentrations do not exceed the current condition at any time during the variance. To ensure that the requirements of the DSV do not result in any lowering of currently attained ambient water quality, the commission relies on the implementation of numeric initial effluent limits to be developed in a method consistent with the division's policy for current condition temporary modifications (Clean Water Policy 13). The DSV will expire on 6/30/2031.

A comprehensive alternatives analysis demonstrated that compliance with the ammonia WQBELs would cause substantial and widespread adverse social and economic impacts in the area where the discharge is located. Alternatives that would achieve compliance, such as replacing the lagoon with a mechanical plant or consolidation with the nearest city, would result in costs that the entity would not be able to pay while still operating a viable business. The commission determined that closing the mobile home park would result in the loss of affordable housing to the typically low-income residents of Vista Verde.

The commission adopted a DSV with an alternative effluent limit that is based upon the expected ammonia effluent quality that will be achieved through feasible improvements to the lagoon. There is some uncertainty in the final effluent quality that will be achieved. Vista Verde will collect additional data to characterize the effectiveness of the improvements, which the commission will review upon re-evaluation of the AEL at future hearings. Since the basis for this DSV is economic feasibility, at future re-evaluations of the DSV, the commission will review whether economic conditions have changed in a way that would make additional reductions in ammonia feasible.

The commission expects that Vista Verde will submit a progress report including updated facility data and improvements to date for the commission's review of the DSV and the AEL at the June 2022 and June 2027 rulemaking hearings. The commission will re-evaluate the requirements of the DSV at these rulemaking hearings, and will consider whether the information at that time demonstrates an ability to reliably achieve lower ammonia concentrations than the AEL originally adopted. If warranted, the commission will modify the AEL to reflect the highest attainable condition.

B. La Plata Segment 10

The commission adopted a DSV for La Plata Segment 10 (COSJLP10) for ammonia that represents the highest degree of protection of the classified use that is economically feasible for the Town of Dove Creek. The ammonia AEL is 20 mg/L from November through May and 10 mg/L from June through October. The seasonal change in limits is intended to address changes in treatment performance due to temperature. Since aerated lagoons have long detention times (greater than 30 days) and do not provide the opportunity to control for daily variation, the AELs shall apply to both the acute and chronic WQBELs. The DSV requires that the Town of Dove Creek's ammonia effluent concentrations do not exceed the current condition at any time during the variance. To ensure that the requirements of the DSV do not result in any lowering of currently attained ambient water quality, the commission relies on the implementation of numeric initial effluent limits to be developed in a method consistent with the division's policy for current condition temporary modifications (Clean Water Policy 13). The DSV will expire on 6/30/2025.

A comprehensive alternatives analysis demonstrated that compliance with the ammonia WQBELs would cause substantial and widespread adverse social and economic impacts in the area where the discharge is located. Treatment that would allow the Town of Dove Creek to meet the ammonia WQBELs, such as replacing the lagoon with a mechanical plant, would result in user fees that exceed the community's ability to pay. The commission determined that any alternative that would result in user fees exceeding 1.25% of median household income for the Town of Dove Creek's residents was economically infeasible at this time, due to the current economic conditions in the Town of Dove Creek, including a high level of debt per capita and a local median household income that is significantly lower than the State's average.

The commission adopted a DSV with an AEL that is based upon the expected ammonia effluent quality that will be achieved through feasible improvements to the lagoon. There is some uncertainty in the final effluent quality that will be achieved. Dove Creek will collect additional data to characterize the effectiveness of the improvements, which the commission will review upon re-evaluation of the AEL The commission expects that Dove Creek will submit a progress report for the commission's review of the DSV and the AEL at the June 2022 rulemaking hearing. The requirements of the DSV will be reviewed during the re-evaluation rulemaking hearing, and will either remain as the AEL identified at the time of the adoption of the variance or be modified to reflect the highest attainable condition. If a subsequent variance is warranted, the Town of Dove Creek may propose a new DSV at the December 2024 rulemaking hearing.