5 Colo. Code Regs. § 1002-38.108
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
The commission initiated this rulemaking hearing upon its own motion pursuant to section 25-8-207, C.R.S. to review the consistency of use classifications and standards for certain segments in the Upper and Middle South Platte Rivers, and specifically to determine whether such classifications and standards were adopted based on material assumptions that were in error or no longer apply (§ 25-8-207(1)(b), C.R.S.; Regulation #31, § 31.6(3)(b)(iii)).
During the Regulation #93 hearing process in 2023, it came to the commission's attention that there was disagreement between the City and County of Denver (Denver) and the division staff concerning the intent behind the descriptions in Regulation #38 (Classifications and Numeric Standards for South Platte River Basin, Laramie River Basin, Republican River Basin, Smoky Hill River Basin) for certain segments in the Upper South Platte and Middle South Platte River basins that flow through Denver International Airport (DEN) property.
In the 2023 Regulation #93 proceeding, the division proposed to include Upper South Platte Segment 16c (COSPUS16c) on Colorado's 303(d) List of Impaired Waters for E. coli and selenium. Segment COSPUS16c is an "all tributaries" segment to the Upper South Platte River to which table value standards apply. The division's Storymap, Colorado's Integrated Water Quality Monitoring and Assessment Report to report on the status of Colorado's streams and lakes, and other division documents indicated that certain small tributaries running through DEN property were included in COSPUS16c. The division's inclusion of these small tributaries in COSPUS16c was based on its reading of segment descriptions adopted during a Regulation #38 rulemaking hearing in 2004, where Denver had proposed resegmentation and site-specific standards for the segments flowing through DEN property.
Denver, on the other hand, had a different understanding of its 2004 proposal, and accordingly sought clarification from the commission in the context of Regulation #93 that the small tributaries at-issue were instead part of Upper South Platte Segments 16d, 16e, and 16f (COSPUS16d, COSPUS16e, and COSPUS16f, respectively), and Middle South Platte Segment 3b (COSPMS03b) - and not the segment proposed for listing, COSPUS16c.
The commission ultimately adopted the division's Regulation #93 proposal for the listing of COSPUS16c as impaired for E. coli and selenium, while noting in the Statement of Basis and Purpose that it agreed with the division's reading that the small tributaries on the DEN property were part of that segment. The commission denied a subsequent motion for reconsideration by Denver but directed the division and Denver to work together for a resolution to the disagreement about the DEN segment descriptions.
To carry out this directive, division and commission staff conducted a comprehensive review of the 2004 Regulation #38 hearing record and discovered documentation indicating that the division had asked Denver, in delineating the upstream point of the proposed new segments, to change the term "headwaters" in its proposal to "from the source." The commission views this as evidence of the parties' intent to include the "sources" (i.e., the small tributaries) for segments COSPUS16d, COSPUS16e, COSPUS16f, and COSPMS03b in those respective segments, rather than including them in the "all tributaries" segment COSPUS16c.
Section 25-8-207(2) instructs the commission to establish appropriate classifications and standards where it finds an existing inconsistency that is based on erroneous "material assumptions." The commission hereby finds the "material assumption" that the 2004 Regulation #38 rulemaking resulted in the small tributaries at-issue being part of COSPUS16c (including the standards and classifications that are attached to that segment) was in error. Through the current rulemaking, the commission seeks to correct this inconsistency and to clarify Denver and the division's (and therefore the commission's) intent behind the 2004 Regulation #38 segment descriptions, as demonstrated through evidence in the 2004 hearing record. This is being accomplished by adding the words "including all tributaries" to the descriptions for segments COSPUS16d, COSPUS16e, COSPUS16f, and COSPMS03b. The commission hereby declares the classifications and standards for COSPUS16c as they previously applied to the small tributaries at-issue void ab initio and simultaneously attaches the standards and classifications for segments COSPUS16d, COSPUS16e, COSPUS16f, and COSPMS03b to those small tributaries, as appropriate.
5 CCR 1002-38.108