5 Colo. Code Regs. § 1002-33.59
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, 2019 to determine whether the temporary modification should be modified, eliminated, or extended.
No action: The commission took no action on the temporary modifications on the following segments:
Blue River Segment 14: temporary modification of the molybdenum standard (expires 12/31/2018). The commission took no action on this temporary modification.
Extension:
Yampa River Segments 13b, 13d, 13e, 13g, 13h, 13i, and 13j: temporary modifications of the iron standards (Segments 13d and 13i, expire 12/31/2018) and selenium standards (Segments 13b, 13d, 13e, 13g, 13i, expire 12/31/2018) were reviewed. Based on evidence submitted by Peabody Sage Creek Mining Company, Seneca Coal Company, and Twentymile Coal, LLC (Peabody) that demonstrated a need for additional time to resolve the uncertainty in the underlying standards, the commission extended the iron temporary modifications on Yampa River segments 13d and 13i. The commission also extended the temporary modifications of the selenium standards on Yampa River segments 13b, 13d, 13e, 13g, and 13i, and adopted temporary modifications of the selenium standards of Yampa River Segments 13h and 13j.
Iron
Peabody originally proposed ambient-based iron standards for Yampa River Segment 13i and revised ambient-based iron standards for Yampa River Segment 13d. However, the commission decided instead to extend the temporary modifications. The commission found that there is still uncertainty about the potential for iron concentrations to stabilize over time, the potential for iron concentrations to improve with additional reclamation activities, and the spatial and seasonal variability of the natural or irreversible iron concentrations. The commission reviewed the revised plan to resolve uncertainty submitted by Peabody and determined that additional time is required for data collection. Peabody revised its proposal to seek extensions of the temporary modifications and agreed to continue to characterize the spatial and temporal variability of iron in these segments. The commission extended the current conditions temporary modifications for iron on Segments 13d and 13i with an expiration date of 6/30/2023.
Selenium
Peabody had originally proposed site-specific criteria-based standards for Yampa River Segments 13b, 13d, 13e, 13g, and 13i, and site-specific ambient-based standards for Yampa River Segments 13h and 13j. Based on discussions with the division, and due to the lack of final guidance on EPA selenium criteria as well as ongoing Colorado-specific selenium studies, Peabody revised its proposal to seek extensions and adoptions of selenium temporary modifications on these segments. Based on the evidence presented by Peabody, the commission extended the temporary modifications for selenium on Yampa River Segments 13b, 13d, 13e, 13g, and 13i, and adopted temporary modifications for selenium on Segments 13h and 13j, as follows:
Yampa River Segment 13b: Selenium(chronic) = current condition for Foidel and Middle Creeks, expiration date of 12/31/2022
Yampa River Segments 13d, 13e, 13g, 13h, 13i, and 13j: Selenium(chronic) = current condition, expiration date of 12/31/2022
If compliance and permitting issues on Cow Camp (in Segment 13g) and Little Grassy (in Segment 13i) creeks are resolved sooner than 12/31/2022 and eliminate the need for temporary modifications on these waterbodies, the commission can modify the temporary modifications during the June 2019 Upper Colorado River basin review, the 2020 Temporary Modifications hearing, or the 2021 Temporary Modifications hearing, when these temporary modifications are scheduled for review.
Typographical and other corrections:
The commission made edits to improve clarity and correct typographical errors in section 33.6 and the corresponding tables for Yampa River sub-basin segments.
New temporary modifications of the arsenic standard:
Consistent with the actions taken in 2013, the commission adopted a temporary modification of the arsenic standard on segments on the following list, with an expiration date of 12/31/2021. At the April 8, 2013 rulemaking, the commission heard testimony that concurred with the finding from a December 13, 2011 rulemaking hearing that an initial reasonable lower limit of treatment technology for arsenic is 3.0 µg/L, pending further investigation by the division, dischargers and stakeholders. The temporary modification was established by the commission to allow for a temporarily less stringent application of the chronic arsenic standard in control requirements for both existing discharges and new or increased discharges.
Upper Colorado Segment 2
Blue River Segment 2a
Roaring Fork Segment 12
Yampa River Segment 2a
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-33.59