5 Colo. Code Regs. § 1002-32.56
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
Pursuant to the requirements in the Basic Standards (at 31.7(3)), the Commission reviewed the status of temporary modifications scheduled to expire before December 31, 2017, to determine whether the temporary modification should be modified, eliminated or extended. Temporary modifications of standards on twelve segments were reviewed.
The Commission took no action on the temporary modifications on the following segments.
Middle Arkansas segment 6b (Lower St Charles River): Temporary modification of the temperature standard. The Commission made no change to the expiration date of 6/30/2017 as the original time allotment was deemed adequate to resolve the uncertainty.
The Commission deleted the temporary modifications on the following segments.
Lower Arkansas segments 3a, 3b, 4b, 5b, 5c, 6a, 6b, 15, 16 and 17: Temporary modification of the temperature standard. The Commission deleted these temporary modifications because they were no longer needed.
The Commission extended the expiration date of temporary modifications on the following segments.
Lower Arkansas segment 1a: Temporary modification of the selenium and sulfate standard. The Commission extended the expiration dates to 12/31/2018 to allow time for the City of Pueblo to pursue a discharger-specific variance (DSV). The Commission reviewed Pueblo's plan for resolving the uncertainty with the underlying standard and found that the remaining uncertainty (the details of the DSV) can be resolved in this time even though all the facets of source control and treatment optimization will not be resolved in this timeframe. The two major tasks for the Division and Pueblo are to develop the Alternative Effluent Limit and to fully articulate the compliance schedule.
The Commission found that keeping the "existing quality" temporary modification in place will not allow any increased impact on the uses of the stream in segment 1a or in waters located downstream. The Commission also notes that if, due to unforeseen circumstances, the City of Pueblo and the Division anticipate that they will be unable to complete the work by January 2018 (to meet the June hearing schedule), an extension of the temporary modification can be considered in the temporary modification rulemaking hearings in December 2016 or December 2017.
The Commission added temporary modifications on the following segment.
Upper Arkansas segment 8b (lower Iowa Gulch): Temporary modification of the temperature, cadmium (chronic) and zinc (chronic) standards: The Commission made no change to the expiration date of 12/31/2017, but expanded the temporary modification to include an acute zinc standard of 754 ug/L, with the same expiration date. Resurrection Mining Company provided data predicting a compliance issue associated with its permitted discharge on segment 8b and there is still uncertainty as to the appropriate acute and chronic standard for segment 8b. The acute value is equal to the 95th percentile of the same data set presented to calculate the chronic temporary modification in the 2013 Basin Hearing. It is understood that Resurrection Mining Company will collect and evaluate additional data during the temporary modification period to better define the uses and appropriate acute and chronic water quality standards for segment 8b.
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-32.56