5 Colo. Code Regs. § 1002-36.46
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
Rio Grande segments 4a and 7 (CORGRG04a and CORGRG07): The commission adopted a two year delay for the effective dates of the Tier 1 and Tier 2 feasibility-based standards on segments 4a and 7.
In the 2018 Rio Grande Basin rulemaking hearing, the commission adopted ambient-based site-specific standards for multiple metals on segments 4a and 7 (36.42(K)). The commission also revised the existing tiered feasibility-based standards based on improvements in water quality tied to future reopening of the Bulldog Mine. The ambient-based standards were to be effective until 12/31/2021, when the Tier 1 feasibility-based standards became effective. Tier 1 standards were to be effective for two years (2022-2023), and then Tier 2 would become effective (1/1/2024).
In the 2018 hearing, the commission directed Rio Grande Silver, Inc. (RGS) to provide an update to the commission in December 2020 regarding the status of the Bulldog Mine operations and tiered standards (36.42(K)). RGS provided an update in this hearing, and based on the water quality data and projected timing of reopening of the Bulldog Mine, proposed to delay the effective date of the tiered feasibility-based standards by two years because reopening the mine is still not economically viable. RGS also presented a longevity plan for ongoing collection of data from all assessment locations (36.6(4)(b) and (c)) to ensure the site-specific standards can be reviewed and updated as needed during future reviews. The data collection effort will be a collaboration between local non-profit groups, CDPHE, and RGS. Understanding that local non-profit groups and CDPHE may not be able to sample all sites in all years due to funding or staffing limitations, RGS has committed to contributing additional sampling effort as needed to maintain a continuous dataset.
The commission adopted this proposal based on the data, information, and longevity plan presented by RGS. The ambient-based site-specific standards adopted in 2018 will continue to apply on segments 4a and 7 until the new expiration date of 12/31/2023. The Tier 1 feasibility-based standards will become effective on 1/1/2024 and expire 12/31/2025, and the Tier 2 standards will become effective on 1/1/2026. No changes were made to the ambient or feasibility-based standards, as they continue to represent the highest attainable ambient quality and feasibility-based quality upon mine reopening, respectively.
The commission will reevaluate these standards at the 2023 Rio Grande Basin rulemaking hearing.
5 CCR 1002-36.46