5 Colo. Code Regs. § 1002-33.27
The provisions of 25-8-202(1)(b) and (2); and 25-8-204 and 25-8-402, C.R.S. 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:
In this rulemaking proceeding, the Commission (1) reaffirmed the existing acute and chronic unionized ammonia standards for Segment 6c of the Upper Colorado River Basin and (2) extended the temporary modification for un-ionized ammonia for that segment. With respect to the temporary modification, the Commission understands that existing quality is based on instream monitoring data collected by the District from 1992 through 1995, at the upper boundary of Segment 6c and reflects the District's existing monthly average discharge levels up to 15 mg/l total ammonia.
In December, 1990, former Upper Colorado River Basin Segment 6 was resegmented into Segments 6a, 6b and 6c, due to differing water quality conditions in the three new segments. A temporary modification for un-ionized ammonia, set at ambient to reflect existing conditions of discharge and agricultural activities, was established for Segment 6c to allow Three Lakes Water and Sanitation District ("Three Lakes") time to conduct water quality monitoring and aquatic biological surveys of the segment, for the purpose of consideration of site-specific standards. In 1993 and 1994, the temporary modification was extended to allow Three Lakes to continue sampling and collecting data on Segment 6c. When the temporary modification was extended in 1994, the Commission also scheduled a rulemaking hearing for November, 1995, to consider revisions to the use classifications and/or water quality standards for Segment 6c based on the data collected by Three Lakes.
The results of Three Lakes water chemistry monitoring and aquatic biological surveys of Segment 6c indicate that its habitat substantially limits any resident population or natural reproduction of fish species; most of the fish found in the segment are transient from water diversion structures. The Division and EPA remain concerned about the potential impact of un-ionized ammonia contained in the Three Lakes's effluent on aquatic life in the segment. Three Lakes presented evidence and testimony that the cost of providing capital improvements sufficient to meet the underlying standards for the benefit of the few transient fish found in the segment was estimated at 4 million dollars. Three Lakes District is a rural public entity with a limited tax and revenue base to finance any needed capital improvements.
The Commission in this rulemaking hearing approved a five year temporary modification, subject to review at approximately a three year interval into such modification. The parties to this rulemaking have entered into a stipulation which forms the basis for the action now being taken by the Commission. The Commission understands that under the stipulation Three Lakes shall comply with the following terms:
The Commission has determined that the temporary modification is consistent with Colorado's Basic Standards and EPA's recent policy statement on variances from water quality standards (October 18, 1995 letter from EPA). The underlying ammonia standards which are adopted as part of this rulemaking are adequate to protect public health and the limited aquatic environment of the unnamed tributary and the aquatic life in Willow Creek. Nothing in this Statement of Basis and Purpose shall be construed as prohibiting any person, including the parties to this rulemaking, from requesting review or revision of these underlying standards at some future time.
PARTIES TO THE RULEMAKING
5 CCR 1002-33.27