5 Colo. Code Regs. § 1002-33.13
The Water Quality Control Commission supports the request to set seasonal standards of 2.1 mg/l for total iron and 1.6 mg/l for total manganese for Segment 13 of Tenmile Creek. Segment 13 is defined as the mainstem of Tenmile Creek from the Climax Parshall Flume to a point immediately above the confluence of West Tenmile Creek and all tributaries, lakes and reservoirs from the source of Tenmile Creek to a point immediately above the confluence with West Tenmile Creek except for specific listing in Segment 15.
The current water quality standards for iron and manganese during the snowmelt bypass period in Segment 13 of Tenmile Creek are based on "Table Value" water quality standards of 1.0 mg/l whereas the actual ambient water quality of iron and manganese during the snowmelt bypass is 2.1 mg/l and 1 6 mg/l. respectively based on a calculation of x[BAR] + s. Hence, assuming zero low flow, as was done by the Division in the discharge permit under which AMAX is operating, the effluent limitations for iron and manganese cannot be met during the snowmelt bypass period. The snowmelt bypass period is defined as any contiguous period of time not to exceed 60 days commencing not earlier than May 1 and terminating not later than July 31.
Seasonal standards for cyanide, cadmium, copper, lead, and zinc were set for Segment 13 in December, 1982. Those standards were proposed after lengthy discussions between Climax Molybdenum, Colorado Division of Wildlife and Water Quality Control Division. At that time the attention was focused on those parameters that are specified in the BAT requirements for the ore mining and dressing industry, the reasoning being that a minimum of BAT limits would be required for any snowmelt bypass. Iron and manganese, which are not included in BAT requirements and are also in exceedence of the stream standards during snowmelt bypass periods (attachment), were inadvertently neglected in the proposal for seasonal standards.
Discussions between the Water Quality Control Division and the Colorado Division of Wildlife concluded that the proposed seasonal standards for iron and manganese which are only applicable during the snowmelt bypass period would have no significant impact on the aquatic life use classification of Segment 13. Also, the Commission is convinced that downstream water supplies will not be impacted by this action. The snowmelt bypass period is defined as any continuous period of time not to exceed 60 days commencing not earlier than May 1 and terminating not later than July 31.
These standards are consistent with the Commission's practice of adopting water quality standards based on instream quality where the data indicates that Table Values are exceeded, but existing uses are nevertheless adequately protected.
During this period (snowmelt bypass) it becomes economically unreasonable, if not impossible, to provide treatment for the large flow of runoff water that comes into contact with the Tailings Ponds located in the Tenmile Basin. Evidence indicates the standards adopted do not require additional technology and are economically reasonable.
The discharge permit issued by the Division includes effluent limitations for iron and manganese during the snowmelt bypass period that cannot be met. As recognized in the Statement of Basis and Purpose, it is economically unreasonable, if not impossible, to provide treatment to achieve the iron and manganese limits during this time.
The specific statutory authority for these amendments is C.R.S. Section 25-8-204.
FISCAL IMPACT STATEMENT
As in the 1982 rulemaking proceedings, the principal fiscal impact of the adoption of the revised water quality standards is a significant potential cost savings to be realized by AMAX. Evidence submitted by AMAX in the 1982 proceedings suggests that without the proposed modifications, AMAX would be faced with additional treatment costs from $8.2 million to $14.6 million in capital expenses and from $3.8 million to $6.6 million in annual operating and maintenance costs. Because the evidence in this proceeding, as well as that of the 1982 proceeding, suggests that the beneficial uses that are identified and in place will be adequately protected with these changes, and because potential beneficial use improvements to be realized by the additional treatment do not bear a reasonable relationship to the costs to attain them, the Commission concludes that it is economically reasonable to support the revision of the iron and manganese standards for the snowmelt bypass period on Segment 13.
5 CCR 1002-33.13