5 Colo. Code Regs. § 1002-38.66
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:
Fort Collins originally proposed site-specific water effect ratios for Segments 11 and 12 of the Cache la Poudre River using a combination of the streamlined Water Effect Ratio (WER) and the Biotic Ligand Model (BLM). Similar proposals were submitted by two parties in the June 2007 Arkansas River Basin hearing. These proposals were opposed by the Division and EPA who recommended that type iii temporary modifications be adopted pursuant to Regulation 31.7(3)(a)(iii). Ultimately in the Arkansas Basin hearing, the Commission adopted temporary modifications of "current condition" with an expiration date of December 31, 2009. Fort Collins modified its proposal in this proceeding accordingly.
This temporary modification recognizes the uncertainty created by the evolving guidance regarding use of the WER, BLM, or other appropriate copper standard to protect the aquatic life use, as well as uncertainty about whether protective levels can feasibly be attained in the effluent of the Fort Collins WWTF. An additional source of uncertainty is whether or not a translator study will provide adequate relief for the WWTF.
The temporary modification has been set to expire on December 31, 2009. During the term of the temporary modification, Fort Collins will investigate the efficacy of a translator from dissolved criterion to a potentially dissolved (or total recoverable) permit limit. In addition, the Commission anticipates that there will be an expanded dialogue between EPA, the Division and interested parties regarding the appropriate methods for setting site-specific copper stream standards.
With a 2009 expiration date, Fort Collins' progress will be reported to the Commission at the December 2007 and December 2008 annual Temporary Modification Review hearing, and the need for the temporary modification will be reviewed at that time. If a translator is inadequate, the Commission recognizes that more time may be needed to develop a site-specific standards proposal.
The temporary modification is set at "current condition." It is the intention of the Commission that when implementing this temporary modification in a CDPS permit, and interpreting the term current condition, the division will assess the current effluent quality, recognizing that it changes over time due to variability in treatment plant removal efficiency and influent loading from industrial, commercial, and residential sources. One necessary element of an approach to maintain the current condition would be a requirement that the total loading from commercial and industrial contributors be maintained at that level as of the date of adoption of the temporary modification and that neither the concentration nor the frequency of high concentration shall increase over historic levels and frequency.
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-38.66