5 Colo. Code Regs. § 1002-33.65
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
Pursuant to the requirements in the Basic Standards (at 31.7(3)), the commission reviewed the status of temporary modifications scheduled to expire before December 31, 2022 to determine whether the temporary modification should be modified, eliminated, or extended.
For the temporary modifications set to expire after the effective date of this hearing, the commission reviewed progress toward resolving the uncertainty in the underlying standard and/or the extent to which conditions are a result of natural or anthropogenic conditions, and evaluated whether the temporary modifications were still justified.
The commission took no action on the following temporary modifications:
Yampa River Segment 2b (COUCYA02b): temporary modification of the chronic temperature standard (expires 12/31/2024). As requested by the commission in 2019 at 33.62(I), the City of Steamboat Springs provided an update on its work to resolve the uncertainty in the chronic temperature standard. Steamboat continues to make progress on resolving the uncertainty and eliminating the need for the temporary modification and determining the extent to which the existing quality is the result of natural or irreversible human-induced conditions. The commission made no change to the expiration date, as the original time allotment was deemed adequate to resolve the uncertainty.
The operative value of the temporary modification is the narrative "current conditions". In future reviews of this temporary modification, the commission will use the following values to compare to the most recent five years of representative effluent data to determine if effluent quality is maintained and ensure that the existing uses are protected. These values are for use by the commission in future reviews of the temporary modification and are not intended to direct implementation of "current condition" temporary modifications in permits:
Data to characterize the status quo of the waterbody are being collected, but adequate data are not available at this time. It is the commission's expectation that as more data become available to characterize instream waterbody temperature conditions, representative numeric values to represent instream status quo will be determined as soon as possible for the commission's use in future reviews of this temporary modification.
Yampa River segments 13e, 13g, 13i, 13j (COUCYA13e, COUCYA13g, COUCYA13i, COUCYA13j): temporary modifications of the chronic selenium standard (expire 12/31/2022). Peabody Sage Creek Mining, LLC, Seneca Properties, LLC, and Twentymile Coal, LLC (Peabody) provided an update to the commission on progress being made on its selenium study and its plan to develop a proposal for site-specific selenium standards in the December 2021 temporary modifications rulemaking hearing. Peabody provided data that demonstrated instream nonattainment of the underlying standard and demonstrated or predicted water quality-based effluent limit compliance problems.
Peabody's plan to resolve uncertainty includes extensive data collection to develop site-specific selenium standards. In previous hearings, the commission has found there was uncertainty regarding the water quality standards necessary to protect current and/or future uses, and uncertainty about the extent to which existing quality is the result of natural or irreversible human-induced conditions. Therefore, to resolve the uncertainty regarding reversibility, the commission expects that any future proposal by Peabody will adequately characterize the extent to which existing conditions are human-induced and include an evaluation of the feasibility of reversing anthropogenic impacts.
Because Peabody intends to propose site-specific standards at the December 2021 temporary modifications rulemaking hearing, the commission did not adopt numeric operative values to determine if the status quo is being maintained during the temporary modification. The commission does not intend that these temporary modifications will be extended. However, if Peabody's proposal is delayed, representative numeric values to characterize instream and effluent status quo to facilitate future evaluations of status quo preservation and ensure existing use protection will be adopted at the next temporary modifications hearing.
The commission deleted temporary modifications on the following segments:
Yampa River segments 13b, 13d, 13h (COUCYA13b, COUCYA13d, COUCYA13h): temporary modifications of the chronic selenium standard (expire 12/31/2022). The commission deleted the temporary modifications on segments 13b and 13d because instream selenium data show that the underlying chronic selenium standard is being attained. The commission also deleted the temporary modification on Segment 13h due to a lack of evidence of a demonstrated or predicted water quality-based effluent limit compliance problem on Segment 13h or upstream in Segment 13d.
5 CCR 1002-33.65