5 Colo. Code Regs. § 1002-38.93
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 limits 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 (WQBEL) 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 re-examine all DSVs not less than once every three years. For purposes of EPA's notice requirement, the Commission's re-evaluation can be completed at two different points:
The Commission adopted a DSV for Upper South Platte River Segments 15 and 16i for selenium that represents the highest degree of protection of the classified uses that is feasible for the Suncor Energy (U.S.A.) Inc. Commerce City Refinery. For selenium, the effluent limits for Suncor shall not be more restrictive than a 30-day average of 24 µg/L prior to 12/31/2023. During the duration of the DSV, Suncor will continue to study selenium treatment optimization and technologies to inform future Commission review of the DSV. 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 also expects that Suncor will submit a progress report for the Commission's review of the DSV and the AEL during the June 2020 South Platte Basin rulemaking hearing. 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 the Suncor DSV will be completed at the effective date of the June 2020 South Platte Basin rulemaking hearing, and the Commission will submit the results of the re-evaluation to EPA no later than 30 days after the effective date of the South Platte Basin 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 1002-38.93