5 Colo. Code Regs. § 1002-35.43
The provisions of C.R S. 25-8-202 (1)(a), (b) and (2); 25-8-203; 25-8-204; and 25-8-402; provide the specific statutory authority for adoption of these regulatory amendments. The Commission also adopted in compliance with 24-4-103(4) C.R.S. the following statement of basis and purpose.
BASIS AND PURPOSE
In 2010, the Commission adopted the discharger specific variance (DSV) provisions at Regulation 31.7(4), which allow a temporary water quality standard to be adopted in cases where water quality based effluent limit (WQBELs) are not feasible to achieve. A DSV is a hybrid standard that maintains the long-term water quality goal of fully protecting all designated uses, while temporarily authorizing an alternative effluent limit (AEL) to be developed for a specific pollutant and specific point source discharge where compliance with the water quality based effluent limit is not feasible.
Pursuant to 40 CFR 131.14(b)(1)(v)-(vi), the Commission must re-evaluate every DSV with a duration longer than five years and provide EPA notice of the results within 30 days of the completion of the re-evaluation process. If the Commission does not complete this action, the federal regulation states that the DSV will no longer be the applicable water quality standard for purposes of the Clean Water Act. This re-evaluation is consistent with Commission Regulation 31.7(4), which requires that the Commission reexamine all DSVs not less than once every three years. For purposes of EPAs notice requirement, the Commission's re-evaluation can be completed at two different points:
The Commission adopted a DSV for San Miguel Segment 12b for ammonia that represents the highest degree of protection of the classified use that is economically feasible for the Town of Nucla. For ammonia, effluent limits for the Town of Nucla shall not be more restrictive than 30-day average effluent limits of 13.8 mg/L from November through April, and 8.3 mg/L from May through October prior to 12/31/2026. The Commission adopted a 30-day average alternative effluent limit because proposed improvements are anticipated to reduce average effluent ammonia concentrations. The proposed improvements do not provide the opportunity to control for variation in the daily maximum effluent concentrations and therefore, an acute limit would not be an appropriate regulatory mechanism to determine whether implementation of the selected alternative was successful.
The Town of Nucia submitted evidence tinat meeting tine ammonia WQBEL 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 NucIa 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 1.5% of median household income for the Town of Nucla's residents was economically infeasible at this time, due to the current economic conditions in the Town of NucIa, including a declining population and a local median household income that is significantly lower than the State's average.
The Commission adopted a DSV with an alternative effluent limit that is based upon the expected ammonia effluent quality that will be achieved through implementation of the selected alternative, which includes improvements to the lagoon. There is some uncertainty in the final effluent quality that will be achieved. This uncertainty may be addressed during future re-evaluations. The Town of NucIa 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 way that would make additional reductions in ammonia feasible.
The Commission expects that the Town of NucIa will submit a progress report for the Commission's review of the DSV and the AEL during the June 2017 and June 2022 Gunnison River Basin review rulemaking hearings. The Commission will conduct a re-evaluation of the DSV during the triennial review process for this regulation. At the time of the issues scoping hearing and the issues formulation hearing for this regulation, the Division will review all existing and readily available information and provide comments to the Commission regarding whether the DSV continues to be the highest attainable condition. The Commission will obtain public input on the re-evaluation through the triennial review process. For purposes of EPA's notice requirement, the Commission's re-examination of this DSV will be completed at the effective date of the 2017 and 2022 Gunnison River Basin rulemaking hearings, and the Commission will submit the results of the re-evaluation to EPA no later than 30 days after the effective date of the rulemaking. The requirements of the DSV will be either the AEL identified at the time of the adoption of the variance, or the highest attainable condition identified during any re-evaluation rulemaking hearing held by the Commission.
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-35.43