5 Colo. Code Regs. § 1002-37.27
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 determined that a new segment was warranted to separate ephemeral reaches of streams in the Grand Valley from Lewis Wash to West Salt Creek and between the base of the Book Cliffs at 5,200 feet elevation to the Government Highline Canal, which are currently in Lower Colorado segment 13a.
Lower Colorado River Basin Re-segmentation - New Segment 13e
The Commission created Lower Colorado segment 13e, which includes ephemeral streams that support extremely limited or rudimentary aquatic life north of the Colorado River, and separates these streams from the perennial and intermittent streams in segment 13a. The Commission specifically excluded the potentially perennial or intermittent headwater portions of the streams by limiting the up-gradient extent of segment 13e at an elevation of 5,200 feet, which approximates the base of the Book Cliffs. This allows for the uppermost headwater reaches of these streams and portions of streams, including the potentially perennial Munger Creek, to remain in segment 13a. In addition. Big Salt Wash, East Salt Creek, and West Salt Creek were identified as streams which are intermittent or perennial; thus, the Commission also specifically excluded these streams from segment 13e.
Lower Colorado segment 13e has Aquatic Life Warm 2, Recreation P, and Agriculture use classifications, and the metals standards for protection of agriculture irrigation uses were retained to provide a level of protection for rudimentary aquatic life, even though irrigated crops are not known to be present in the segment. The Commission noted that information on existing water quality in the segment is limited, because these washes have no base flow, which severely limits the ability to collect water and biological samples. Because of limited sampling data, ambient-based criteria were not calculated. However, the limited sample results available indicated the potential for high levels of arsenic, nickel, zinc and manganese. As additional water-quality data become available in the future, the possibility of ambient-based water quality standards can be revisited.
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-37.27