5 Colo. Code Regs. § 1002-36.18
The provisions of sections 25-8-202 and 25-8-401, C.R.S., provide the specific statutory authority for adoption of the attached regulatory amendments. The Commission also adopted, in compliance with section 24-4-103(4) C.R.S., the following statement of basis and purpose.
BASIS AND PURPOSE
The following revisions to the standards for segments 9a and 9b of the Closed Basin. (Kerber Creek and its tributaries) were made. Changes to the water quality standards for cadmium and selenium in 9a are reflective of the changes to the Basic Standards made in 1994 (cadmium and 1995 (selenium). In addition, a change to the standard for sulfide in 9a was made because the existing standard was erroneously listed as the value for an aquatic life use which is not an adopted use for segment 9a. The expiration date for temporary modifications in both 9a and 9b were extended to June 30, 2000. In segment 9b the standards for selenium were also changed to reflect the 1995 changes to the Basic Standards and numeric temporary modifications for cadmium, copper, manganese and zinc were adopted along with a new expiration date. The numeric values for the temporary modifications were based on data collected during low flow in 1994, 95 and 96 by the Group at their station KC-6. The numeric values are intended to represent the existing quality in segment 9b as measured at one point (KC-6) in the segment. The numeric values at monitoring point KC-6 are based only on single measurements made during individual high-flow and low-flow sampling events during the years 1994, 1995 and 1996, and thus do not fully represent the range of metals concentrations that may be observed. Additional data will be collected in 1997 on a more frequent basis at KC-6 to further assess existing quality at KC-6 under a wider range of flow conditions. The expiration date was extended to allow the Group to continue their voluntary cleanup efforts in segments 9a and 9b which began in 1994 and are not expected to be completed until 2000.
It is recognized that the Bonanza Mining District Group (the Group) will direct remedial efforts toward attainment of long-term classification and numeric standard goals. However, attainment of long-term goals may require additional efforts by others to improve physical conditions of the stream and/or address metals loading sources on property over which the Group has no control or responsibility. Long-term classification goals are intended to encourage such efforts.
5 CCR 1002-36.18